2005-04-17 06:20:36 +08:00
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#ifndef __LINUX_PERCPU_H
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#define __LINUX_PERCPU_H
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2006-09-26 14:31:21 +08:00
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2007-07-16 14:39:57 +08:00
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#include <linux/preempt.h>
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2005-04-17 06:20:36 +08:00
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#include <linux/slab.h> /* For kmalloc() */
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#include <linux/smp.h>
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2006-09-26 14:31:21 +08:00
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#include <linux/cpumask.h>
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2009-03-06 13:33:58 +08:00
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#include <linux/pfn.h>
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2006-09-26 14:31:21 +08:00
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2005-04-17 06:20:36 +08:00
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#include <asm/percpu.h>
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2009-03-06 13:33:58 +08:00
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/* enough to cover all DEFINE_PER_CPUs in modules */
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2007-05-03 01:27:11 +08:00
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#ifdef CONFIG_MODULES
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2009-03-06 13:33:58 +08:00
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#define PERCPU_MODULE_RESERVE (8 << 10)
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2007-05-03 01:27:11 +08:00
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#else
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2009-03-06 13:33:58 +08:00
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#define PERCPU_MODULE_RESERVE 0
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2005-04-17 06:20:36 +08:00
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#endif
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2009-03-06 13:33:58 +08:00
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#ifndef PERCPU_ENOUGH_ROOM
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2007-05-03 01:27:11 +08:00
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#define PERCPU_ENOUGH_ROOM \
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2009-03-06 13:33:58 +08:00
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(ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES) + \
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PERCPU_MODULE_RESERVE)
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#endif
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2007-05-03 01:27:11 +08:00
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2006-09-26 14:30:53 +08:00
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/*
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* Must be an lvalue. Since @var must be a simple identifier,
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* we force a syntax error here if it isn't.
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*/
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#define get_cpu_var(var) (*({ \
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preempt_disable(); \
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&__get_cpu_var(var); }))
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2009-10-29 21:34:15 +08:00
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#define put_cpu_var(var) do { \
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(void)(var); \
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preempt_enable(); \
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} while (0)
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2005-04-17 06:20:36 +08:00
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#ifdef CONFIG_SMP
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2009-02-24 10:57:21 +08:00
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/* minimum unit size, also is the maximum supported allocation size */
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2009-03-06 13:33:58 +08:00
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#define PCPU_MIN_UNIT_SIZE PFN_ALIGN(64 << 10)
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2009-02-24 10:57:21 +08:00
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/*
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* PERCPU_DYNAMIC_RESERVE indicates the amount of free area to piggy
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2009-03-06 13:33:59 +08:00
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* back on the first chunk for dynamic percpu allocation if arch is
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* manually allocating and mapping it for faster access (as a part of
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* large page mapping for example).
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2009-02-24 10:57:21 +08:00
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*
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2009-03-06 13:33:59 +08:00
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* The following values give between one and two pages of free space
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* after typical minimal boot (2-way SMP, single disk and NIC) with
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* both defconfig and a distro config on x86_64 and 32. More
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* intelligent way to determine this would be nice.
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2009-02-24 10:57:21 +08:00
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*/
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2009-03-06 13:33:59 +08:00
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#if BITS_PER_LONG > 32
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#define PERCPU_DYNAMIC_RESERVE (20 << 10)
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#else
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#define PERCPU_DYNAMIC_RESERVE (12 << 10)
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#endif
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2009-02-24 10:57:21 +08:00
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2009-02-20 15:29:08 +08:00
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extern void *pcpu_base_addr;
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2009-08-14 14:00:51 +08:00
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extern const unsigned long *pcpu_unit_offsets;
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2005-04-17 06:20:36 +08:00
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percpu: introduce pcpu_alloc_info and pcpu_group_info
Till now, non-linear cpu->unit map was expressed using an integer
array which maps each cpu to a unit and used only by lpage allocator.
Although how many units have been placed in a single contiguos area
(group) is known while building unit_map, the information is lost when
the result is recorded into the unit_map array. For lpage allocator,
as all allocations are done by lpages and whether two adjacent lpages
are in the same group or not is irrelevant, this didn't cause any
problem. Non-linear cpu->unit mapping will be used for sparse
embedding and this grouping information is necessary for that.
This patch introduces pcpu_alloc_info which contains all the
information necessary for initializing percpu allocator.
pcpu_alloc_info contains array of pcpu_group_info which describes how
units are grouped and mapped to cpus. pcpu_group_info also has
base_offset field to specify its offset from the chunk's base address.
pcpu_build_alloc_info() initializes this field as if all groups are
allocated back-to-back as is currently done but this will be used to
sparsely place groups.
pcpu_alloc_info is a rather complex data structure which contains a
flexible array which in turn points to nested cpu_map arrays.
* pcpu_alloc_alloc_info() and pcpu_free_alloc_info() are provided to
help dealing with pcpu_alloc_info.
* pcpu_lpage_build_unit_map() is updated to build pcpu_alloc_info,
generalized and renamed to pcpu_build_alloc_info().
@cpu_distance_fn may be NULL indicating that all cpus are of
LOCAL_DISTANCE.
* pcpul_lpage_dump_cfg() is updated to process pcpu_alloc_info,
generalized and renamed to pcpu_dump_alloc_info(). It now also
prints which group each alloc unit belongs to.
* pcpu_setup_first_chunk() now takes pcpu_alloc_info instead of the
separate parameters. All first chunk allocators are updated to use
pcpu_build_alloc_info() to build alloc_info and call
pcpu_setup_first_chunk() with it. This has the side effect of
packing units for sparse possible cpus. ie. if cpus 0, 2 and 4 are
possible, they'll be assigned unit 0, 1 and 2 instead of 0, 2 and 4.
* x86 setup_pcpu_lpage() is updated to deal with alloc_info.
* sparc64 setup_per_cpu_areas() is updated to build alloc_info.
Although the changes made by this patch are pretty pervasive, it
doesn't cause any behavior difference other than packing of sparse
cpus. It mostly changes how information is passed among
initialization functions and makes room for more flexibility.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
2009-08-14 14:00:51 +08:00
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struct pcpu_group_info {
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int nr_units; /* aligned # of units */
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unsigned long base_offset; /* base address offset */
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unsigned int *cpu_map; /* unit->cpu map, empty
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* entries contain NR_CPUS */
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};
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struct pcpu_alloc_info {
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size_t static_size;
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size_t reserved_size;
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size_t dyn_size;
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size_t unit_size;
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size_t atom_size;
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size_t alloc_size;
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size_t __ai_size; /* internal, don't use */
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int nr_groups; /* 0 if grouping unnecessary */
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struct pcpu_group_info groups[];
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};
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2009-08-14 14:00:50 +08:00
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enum pcpu_fc {
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PCPU_FC_AUTO,
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PCPU_FC_EMBED,
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PCPU_FC_PAGE,
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PCPU_FC_NR,
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};
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extern const char *pcpu_fc_names[PCPU_FC_NR];
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extern enum pcpu_fc pcpu_chosen_fc;
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2009-08-14 14:00:50 +08:00
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typedef void * (*pcpu_fc_alloc_fn_t)(unsigned int cpu, size_t size,
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size_t align);
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2009-07-04 07:10:59 +08:00
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typedef void (*pcpu_fc_free_fn_t)(void *ptr, size_t size);
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typedef void (*pcpu_fc_populate_pte_fn_t)(unsigned long addr);
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2009-07-04 07:11:00 +08:00
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typedef int (pcpu_fc_cpu_distance_fn_t)(unsigned int from, unsigned int to);
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2009-02-20 15:29:08 +08:00
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percpu: introduce pcpu_alloc_info and pcpu_group_info
Till now, non-linear cpu->unit map was expressed using an integer
array which maps each cpu to a unit and used only by lpage allocator.
Although how many units have been placed in a single contiguos area
(group) is known while building unit_map, the information is lost when
the result is recorded into the unit_map array. For lpage allocator,
as all allocations are done by lpages and whether two adjacent lpages
are in the same group or not is irrelevant, this didn't cause any
problem. Non-linear cpu->unit mapping will be used for sparse
embedding and this grouping information is necessary for that.
This patch introduces pcpu_alloc_info which contains all the
information necessary for initializing percpu allocator.
pcpu_alloc_info contains array of pcpu_group_info which describes how
units are grouped and mapped to cpus. pcpu_group_info also has
base_offset field to specify its offset from the chunk's base address.
pcpu_build_alloc_info() initializes this field as if all groups are
allocated back-to-back as is currently done but this will be used to
sparsely place groups.
pcpu_alloc_info is a rather complex data structure which contains a
flexible array which in turn points to nested cpu_map arrays.
* pcpu_alloc_alloc_info() and pcpu_free_alloc_info() are provided to
help dealing with pcpu_alloc_info.
* pcpu_lpage_build_unit_map() is updated to build pcpu_alloc_info,
generalized and renamed to pcpu_build_alloc_info().
@cpu_distance_fn may be NULL indicating that all cpus are of
LOCAL_DISTANCE.
* pcpul_lpage_dump_cfg() is updated to process pcpu_alloc_info,
generalized and renamed to pcpu_dump_alloc_info(). It now also
prints which group each alloc unit belongs to.
* pcpu_setup_first_chunk() now takes pcpu_alloc_info instead of the
separate parameters. All first chunk allocators are updated to use
pcpu_build_alloc_info() to build alloc_info and call
pcpu_setup_first_chunk() with it. This has the side effect of
packing units for sparse possible cpus. ie. if cpus 0, 2 and 4 are
possible, they'll be assigned unit 0, 1 and 2 instead of 0, 2 and 4.
* x86 setup_pcpu_lpage() is updated to deal with alloc_info.
* sparc64 setup_per_cpu_areas() is updated to build alloc_info.
Although the changes made by this patch are pretty pervasive, it
doesn't cause any behavior difference other than packing of sparse
cpus. It mostly changes how information is passed among
initialization functions and makes room for more flexibility.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
2009-08-14 14:00:51 +08:00
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extern struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
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int nr_units);
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extern void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai);
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extern struct pcpu_alloc_info * __init pcpu_build_alloc_info(
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size_t reserved_size, ssize_t dyn_size,
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size_t atom_size,
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2009-08-14 14:00:51 +08:00
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pcpu_fc_cpu_distance_fn_t cpu_distance_fn);
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2009-08-14 14:00:51 +08:00
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extern int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
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void *base_addr);
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2009-02-24 10:57:21 +08:00
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2009-08-14 14:00:49 +08:00
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#ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
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2009-08-14 14:00:52 +08:00
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extern int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
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size_t atom_size,
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pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
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pcpu_fc_alloc_fn_t alloc_fn,
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pcpu_fc_free_fn_t free_fn);
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2009-08-14 14:00:49 +08:00
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#endif
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2009-03-10 15:27:48 +08:00
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2009-08-14 14:00:49 +08:00
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#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
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2009-08-14 14:00:51 +08:00
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extern int __init pcpu_page_first_chunk(size_t reserved_size,
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2009-07-04 07:10:59 +08:00
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pcpu_fc_alloc_fn_t alloc_fn,
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pcpu_fc_free_fn_t free_fn,
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pcpu_fc_populate_pte_fn_t populate_pte_fn);
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2009-08-14 14:00:49 +08:00
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#endif
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2009-07-04 07:10:59 +08:00
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2009-02-20 15:29:08 +08:00
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/*
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* Use this to get to a cpu's version of the per-cpu object
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* dynamically allocated. Non-atomic access to the current CPU's
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* version should probably be combined with get_cpu()/put_cpu().
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*/
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2009-02-20 15:29:08 +08:00
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#define per_cpu_ptr(ptr, cpu) SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu)))
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2009-03-06 13:33:59 +08:00
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extern void *__alloc_reserved_percpu(size_t size, size_t align);
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2009-02-20 15:29:08 +08:00
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extern void *__alloc_percpu(size_t size, size_t align);
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extern void free_percpu(void *__pdata);
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2005-04-17 06:20:36 +08:00
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2009-03-30 18:07:44 +08:00
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#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
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extern void __init setup_per_cpu_areas(void);
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#endif
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2005-04-17 06:20:36 +08:00
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#else /* CONFIG_SMP */
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2009-02-20 15:29:08 +08:00
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#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
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2006-09-26 14:31:21 +08:00
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2009-02-20 15:29:08 +08:00
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static inline void *__alloc_percpu(size_t size, size_t align)
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2006-09-26 14:31:21 +08:00
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{
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2009-02-20 15:29:08 +08:00
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/*
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* Can't easily make larger alignment work with kmalloc. WARN
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* on it. Larger alignment should only be used for module
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* percpu sections on SMP for which this path isn't used.
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*/
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2009-02-26 09:54:17 +08:00
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WARN_ON_ONCE(align > SMP_CACHE_BYTES);
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2009-02-25 21:36:45 +08:00
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return kzalloc(size, GFP_KERNEL);
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2006-09-26 14:31:21 +08:00
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}
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2009-02-20 15:29:08 +08:00
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static inline void free_percpu(void *p)
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2006-09-26 14:31:21 +08:00
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{
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2009-02-20 15:29:08 +08:00
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kfree(p);
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2005-04-17 06:20:36 +08:00
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}
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2009-03-30 18:07:44 +08:00
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static inline void __init setup_per_cpu_areas(void) { }
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2009-07-15 22:35:14 +08:00
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static inline void *pcpu_lpage_remapped(void *kaddr)
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{
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return NULL;
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}
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2005-04-17 06:20:36 +08:00
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#endif /* CONFIG_SMP */
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2009-10-29 21:34:12 +08:00
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#define alloc_percpu(type) \
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(typeof(type) *)__alloc_percpu(sizeof(type), __alignof__(type))
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2005-04-17 06:20:36 +08:00
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2009-04-11 03:02:40 +08:00
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/*
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* Optional methods for optimized non-lvalue per-cpu variable access.
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*
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* @var can be a percpu variable or a field of it and its size should
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* equal char, int or long. percpu_read() evaluates to a lvalue and
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* all others to void.
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*
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* These operations are guaranteed to be atomic w.r.t. preemption.
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* The generic versions use plain get/put_cpu_var(). Archs are
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* encouraged to implement single-instruction alternatives which don't
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* require preemption protection.
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*/
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#ifndef percpu_read
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# define percpu_read(var) \
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({ \
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2009-10-29 21:34:15 +08:00
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typeof(var) *pr_ptr__ = &(var); \
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typeof(var) pr_ret__; \
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pr_ret__ = get_cpu_var(*pr_ptr__); \
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put_cpu_var(*pr_ptr__); \
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pr_ret__; \
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2009-04-11 03:02:40 +08:00
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})
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#endif
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#define __percpu_generic_to_op(var, val, op) \
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do { \
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2009-10-29 21:34:15 +08:00
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typeof(var) *pgto_ptr__ = &(var); \
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get_cpu_var(*pgto_ptr__) op val; \
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put_cpu_var(*pgto_ptr__); \
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2009-04-11 03:02:40 +08:00
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} while (0)
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#ifndef percpu_write
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# define percpu_write(var, val) __percpu_generic_to_op(var, (val), =)
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#endif
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#ifndef percpu_add
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# define percpu_add(var, val) __percpu_generic_to_op(var, (val), +=)
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#endif
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#ifndef percpu_sub
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# define percpu_sub(var, val) __percpu_generic_to_op(var, (val), -=)
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#endif
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#ifndef percpu_and
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# define percpu_and(var, val) __percpu_generic_to_op(var, (val), &=)
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#endif
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#ifndef percpu_or
|
|
|
|
|
# define percpu_or(var, val) __percpu_generic_to_op(var, (val), |=)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef percpu_xor
|
|
|
|
|
# define percpu_xor(var, val) __percpu_generic_to_op(var, (val), ^=)
|
|
|
|
|
#endif
|
|
|
|
|
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
/*
|
|
|
|
|
* Branching function to split up a function into a set of functions that
|
|
|
|
|
* are called for different scalar sizes of the objects handled.
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
extern void __bad_size_call_parameter(void);
|
|
|
|
|
|
2009-10-29 21:34:12 +08:00
|
|
|
#define __pcpu_size_call_return(stem, variable) \
|
|
|
|
|
({ typeof(variable) pscr_ret__; \
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
switch(sizeof(variable)) { \
|
2009-10-29 21:34:12 +08:00
|
|
|
case 1: pscr_ret__ = stem##1(variable);break; \
|
|
|
|
|
case 2: pscr_ret__ = stem##2(variable);break; \
|
|
|
|
|
case 4: pscr_ret__ = stem##4(variable);break; \
|
|
|
|
|
case 8: pscr_ret__ = stem##8(variable);break; \
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
default: \
|
|
|
|
|
__bad_size_call_parameter();break; \
|
|
|
|
|
} \
|
2009-10-29 21:34:12 +08:00
|
|
|
pscr_ret__; \
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
})
|
|
|
|
|
|
2009-10-29 21:34:12 +08:00
|
|
|
#define __pcpu_size_call(stem, variable, ...) \
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
do { \
|
|
|
|
|
switch(sizeof(variable)) { \
|
|
|
|
|
case 1: stem##1(variable, __VA_ARGS__);break; \
|
|
|
|
|
case 2: stem##2(variable, __VA_ARGS__);break; \
|
|
|
|
|
case 4: stem##4(variable, __VA_ARGS__);break; \
|
|
|
|
|
case 8: stem##8(variable, __VA_ARGS__);break; \
|
|
|
|
|
default: \
|
|
|
|
|
__bad_size_call_parameter();break; \
|
|
|
|
|
} \
|
|
|
|
|
} while (0)
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Optimized manipulation for memory allocated through the per cpu
|
2009-10-29 21:34:15 +08:00
|
|
|
* allocator or for addresses of per cpu variables.
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
*
|
|
|
|
|
* These operation guarantee exclusivity of access for other operations
|
|
|
|
|
* on the *same* processor. The assumption is that per cpu data is only
|
|
|
|
|
* accessed by a single processor instance (the current one).
|
|
|
|
|
*
|
|
|
|
|
* The first group is used for accesses that must be done in a
|
|
|
|
|
* preemption safe way since we know that the context is not preempt
|
|
|
|
|
* safe. Interrupts may occur. If the interrupt modifies the variable
|
|
|
|
|
* too then RMW actions will not be reliable.
|
|
|
|
|
*
|
|
|
|
|
* The arch code can provide optimized functions in two ways:
|
|
|
|
|
*
|
|
|
|
|
* 1. Override the function completely. F.e. define this_cpu_add().
|
|
|
|
|
* The arch must then ensure that the various scalar format passed
|
|
|
|
|
* are handled correctly.
|
|
|
|
|
*
|
|
|
|
|
* 2. Provide functions for certain scalar sizes. F.e. provide
|
|
|
|
|
* this_cpu_add_2() to provide per cpu atomic operations for 2 byte
|
|
|
|
|
* sized RMW actions. If arch code does not provide operations for
|
|
|
|
|
* a scalar size then the fallback in the generic code will be
|
|
|
|
|
* used.
|
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#define _this_cpu_generic_read(pcp) \
|
|
|
|
|
({ typeof(pcp) ret__; \
|
|
|
|
|
preempt_disable(); \
|
|
|
|
|
ret__ = *this_cpu_ptr(&(pcp)); \
|
|
|
|
|
preempt_enable(); \
|
|
|
|
|
ret__; \
|
|
|
|
|
})
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_read
|
|
|
|
|
# ifndef this_cpu_read_1
|
|
|
|
|
# define this_cpu_read_1(pcp) _this_cpu_generic_read(pcp)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_read_2
|
|
|
|
|
# define this_cpu_read_2(pcp) _this_cpu_generic_read(pcp)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_read_4
|
|
|
|
|
# define this_cpu_read_4(pcp) _this_cpu_generic_read(pcp)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_read_8
|
|
|
|
|
# define this_cpu_read_8(pcp) _this_cpu_generic_read(pcp)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define this_cpu_read(pcp) __pcpu_size_call_return(this_cpu_read_, (pcp))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#define _this_cpu_generic_to_op(pcp, val, op) \
|
|
|
|
|
do { \
|
|
|
|
|
preempt_disable(); \
|
2009-10-29 21:34:15 +08:00
|
|
|
*__this_cpu_ptr(&(pcp)) op val; \
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
preempt_enable(); \
|
|
|
|
|
} while (0)
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_write
|
|
|
|
|
# ifndef this_cpu_write_1
|
|
|
|
|
# define this_cpu_write_1(pcp, val) _this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_write_2
|
|
|
|
|
# define this_cpu_write_2(pcp, val) _this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_write_4
|
|
|
|
|
# define this_cpu_write_4(pcp, val) _this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_write_8
|
|
|
|
|
# define this_cpu_write_8(pcp, val) _this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_add
|
|
|
|
|
# ifndef this_cpu_add_1
|
|
|
|
|
# define this_cpu_add_1(pcp, val) _this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_add_2
|
|
|
|
|
# define this_cpu_add_2(pcp, val) _this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_add_4
|
|
|
|
|
# define this_cpu_add_4(pcp, val) _this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_add_8
|
|
|
|
|
# define this_cpu_add_8(pcp, val) _this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_sub
|
|
|
|
|
# define this_cpu_sub(pcp, val) this_cpu_add((pcp), -(val))
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_inc
|
|
|
|
|
# define this_cpu_inc(pcp) this_cpu_add((pcp), 1)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_dec
|
|
|
|
|
# define this_cpu_dec(pcp) this_cpu_sub((pcp), 1)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_and
|
|
|
|
|
# ifndef this_cpu_and_1
|
|
|
|
|
# define this_cpu_and_1(pcp, val) _this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_and_2
|
|
|
|
|
# define this_cpu_and_2(pcp, val) _this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_and_4
|
|
|
|
|
# define this_cpu_and_4(pcp, val) _this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_and_8
|
|
|
|
|
# define this_cpu_and_8(pcp, val) _this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define this_cpu_and(pcp, val) __pcpu_size_call(this_cpu_and_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_or
|
|
|
|
|
# ifndef this_cpu_or_1
|
|
|
|
|
# define this_cpu_or_1(pcp, val) _this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_or_2
|
|
|
|
|
# define this_cpu_or_2(pcp, val) _this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_or_4
|
|
|
|
|
# define this_cpu_or_4(pcp, val) _this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_or_8
|
|
|
|
|
# define this_cpu_or_8(pcp, val) _this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define this_cpu_or(pcp, val) __pcpu_size_call(this_cpu_or_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef this_cpu_xor
|
|
|
|
|
# ifndef this_cpu_xor_1
|
|
|
|
|
# define this_cpu_xor_1(pcp, val) _this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_xor_2
|
|
|
|
|
# define this_cpu_xor_2(pcp, val) _this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_xor_4
|
|
|
|
|
# define this_cpu_xor_4(pcp, val) _this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef this_cpu_xor_8
|
|
|
|
|
# define this_cpu_xor_8(pcp, val) _this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define this_cpu_xor(pcp, val) __pcpu_size_call(this_cpu_or_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Generic percpu operations that do not require preemption handling.
|
|
|
|
|
* Either we do not care about races or the caller has the
|
|
|
|
|
* responsibility of handling preemptions issues. Arch code can still
|
|
|
|
|
* override these instructions since the arch per cpu code may be more
|
|
|
|
|
* efficient and may actually get race freeness for free (that is the
|
|
|
|
|
* case for x86 for example).
|
|
|
|
|
*
|
|
|
|
|
* If there is no other protection through preempt disable and/or
|
|
|
|
|
* disabling interupts then one of these RMW operations can show unexpected
|
|
|
|
|
* behavior because the execution thread was rescheduled on another processor
|
|
|
|
|
* or an interrupt occurred and the same percpu variable was modified from
|
|
|
|
|
* the interrupt context.
|
|
|
|
|
*/
|
|
|
|
|
#ifndef __this_cpu_read
|
|
|
|
|
# ifndef __this_cpu_read_1
|
|
|
|
|
# define __this_cpu_read_1(pcp) (*__this_cpu_ptr(&(pcp)))
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_read_2
|
|
|
|
|
# define __this_cpu_read_2(pcp) (*__this_cpu_ptr(&(pcp)))
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_read_4
|
|
|
|
|
# define __this_cpu_read_4(pcp) (*__this_cpu_ptr(&(pcp)))
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_read_8
|
|
|
|
|
# define __this_cpu_read_8(pcp) (*__this_cpu_ptr(&(pcp)))
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define __this_cpu_read(pcp) __pcpu_size_call_return(__this_cpu_read_, (pcp))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#define __this_cpu_generic_to_op(pcp, val, op) \
|
|
|
|
|
do { \
|
|
|
|
|
*__this_cpu_ptr(&(pcp)) op val; \
|
|
|
|
|
} while (0)
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_write
|
|
|
|
|
# ifndef __this_cpu_write_1
|
|
|
|
|
# define __this_cpu_write_1(pcp, val) __this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_write_2
|
|
|
|
|
# define __this_cpu_write_2(pcp, val) __this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_write_4
|
|
|
|
|
# define __this_cpu_write_4(pcp, val) __this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_write_8
|
|
|
|
|
# define __this_cpu_write_8(pcp, val) __this_cpu_generic_to_op((pcp), (val), =)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define __this_cpu_write(pcp, val) __pcpu_size_call(__this_cpu_write_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_add
|
|
|
|
|
# ifndef __this_cpu_add_1
|
|
|
|
|
# define __this_cpu_add_1(pcp, val) __this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_add_2
|
|
|
|
|
# define __this_cpu_add_2(pcp, val) __this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_add_4
|
|
|
|
|
# define __this_cpu_add_4(pcp, val) __this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_add_8
|
|
|
|
|
# define __this_cpu_add_8(pcp, val) __this_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define __this_cpu_add(pcp, val) __pcpu_size_call(__this_cpu_add_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_sub
|
|
|
|
|
# define __this_cpu_sub(pcp, val) __this_cpu_add((pcp), -(val))
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_inc
|
|
|
|
|
# define __this_cpu_inc(pcp) __this_cpu_add((pcp), 1)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_dec
|
|
|
|
|
# define __this_cpu_dec(pcp) __this_cpu_sub((pcp), 1)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_and
|
|
|
|
|
# ifndef __this_cpu_and_1
|
|
|
|
|
# define __this_cpu_and_1(pcp, val) __this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_and_2
|
|
|
|
|
# define __this_cpu_and_2(pcp, val) __this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_and_4
|
|
|
|
|
# define __this_cpu_and_4(pcp, val) __this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_and_8
|
|
|
|
|
# define __this_cpu_and_8(pcp, val) __this_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define __this_cpu_and(pcp, val) __pcpu_size_call(__this_cpu_and_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_or
|
|
|
|
|
# ifndef __this_cpu_or_1
|
|
|
|
|
# define __this_cpu_or_1(pcp, val) __this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_or_2
|
|
|
|
|
# define __this_cpu_or_2(pcp, val) __this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_or_4
|
|
|
|
|
# define __this_cpu_or_4(pcp, val) __this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_or_8
|
|
|
|
|
# define __this_cpu_or_8(pcp, val) __this_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define __this_cpu_or(pcp, val) __pcpu_size_call(__this_cpu_or_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef __this_cpu_xor
|
|
|
|
|
# ifndef __this_cpu_xor_1
|
|
|
|
|
# define __this_cpu_xor_1(pcp, val) __this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_xor_2
|
|
|
|
|
# define __this_cpu_xor_2(pcp, val) __this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_xor_4
|
|
|
|
|
# define __this_cpu_xor_4(pcp, val) __this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef __this_cpu_xor_8
|
|
|
|
|
# define __this_cpu_xor_8(pcp, val) __this_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define __this_cpu_xor(pcp, val) __pcpu_size_call(__this_cpu_xor_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* IRQ safe versions of the per cpu RMW operations. Note that these operations
|
|
|
|
|
* are *not* safe against modification of the same variable from another
|
|
|
|
|
* processors (which one gets when using regular atomic operations)
|
|
|
|
|
. They are guaranteed to be atomic vs. local interrupts and
|
|
|
|
|
* preemption only.
|
|
|
|
|
*/
|
|
|
|
|
#define irqsafe_cpu_generic_to_op(pcp, val, op) \
|
|
|
|
|
do { \
|
|
|
|
|
unsigned long flags; \
|
|
|
|
|
local_irq_save(flags); \
|
|
|
|
|
*__this_cpu_ptr(&(pcp)) op val; \
|
|
|
|
|
local_irq_restore(flags); \
|
|
|
|
|
} while (0)
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_add
|
|
|
|
|
# ifndef irqsafe_cpu_add_1
|
|
|
|
|
# define irqsafe_cpu_add_1(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_add_2
|
|
|
|
|
# define irqsafe_cpu_add_2(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_add_4
|
|
|
|
|
# define irqsafe_cpu_add_4(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_add_8
|
|
|
|
|
# define irqsafe_cpu_add_8(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), +=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define irqsafe_cpu_add(pcp, val) __pcpu_size_call(irqsafe_cpu_add_, (pcp), (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_sub
|
|
|
|
|
# define irqsafe_cpu_sub(pcp, val) irqsafe_cpu_add((pcp), -(val))
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_inc
|
|
|
|
|
# define irqsafe_cpu_inc(pcp) irqsafe_cpu_add((pcp), 1)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_dec
|
|
|
|
|
# define irqsafe_cpu_dec(pcp) irqsafe_cpu_sub((pcp), 1)
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_and
|
|
|
|
|
# ifndef irqsafe_cpu_and_1
|
|
|
|
|
# define irqsafe_cpu_and_1(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_and_2
|
|
|
|
|
# define irqsafe_cpu_and_2(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_and_4
|
|
|
|
|
# define irqsafe_cpu_and_4(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_and_8
|
|
|
|
|
# define irqsafe_cpu_and_8(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), &=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define irqsafe_cpu_and(pcp, val) __pcpu_size_call(irqsafe_cpu_and_, (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_or
|
|
|
|
|
# ifndef irqsafe_cpu_or_1
|
|
|
|
|
# define irqsafe_cpu_or_1(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_or_2
|
|
|
|
|
# define irqsafe_cpu_or_2(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_or_4
|
|
|
|
|
# define irqsafe_cpu_or_4(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_or_8
|
|
|
|
|
# define irqsafe_cpu_or_8(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), |=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define irqsafe_cpu_or(pcp, val) __pcpu_size_call(irqsafe_cpu_or_, (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
|
|
|
|
#ifndef irqsafe_cpu_xor
|
|
|
|
|
# ifndef irqsafe_cpu_xor_1
|
|
|
|
|
# define irqsafe_cpu_xor_1(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_xor_2
|
|
|
|
|
# define irqsafe_cpu_xor_2(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_xor_4
|
|
|
|
|
# define irqsafe_cpu_xor_4(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
|
|
|
|
# ifndef irqsafe_cpu_xor_8
|
|
|
|
|
# define irqsafe_cpu_xor_8(pcp, val) irqsafe_cpu_generic_to_op((pcp), (val), ^=)
|
|
|
|
|
# endif
|
2009-10-29 21:34:12 +08:00
|
|
|
# define irqsafe_cpu_xor(pcp, val) __pcpu_size_call(irqsafe_cpu_xor_, (val))
|
this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations
This patch introduces two things: First this_cpu_ptr and then per cpu
atomic operations.
this_cpu_ptr
------------
A common operation when dealing with cpu data is to get the instance of the
cpu data associated with the currently executing processor. This can be
optimized by
this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id).
The problem with per_cpu_ptr(x, smp_processor_id) is that it requires
an array lookup to find the offset for the cpu. Processors typically
have the offset for the current cpu area in some kind of (arch dependent)
efficiently accessible register or memory location.
We can use that instead of doing the array lookup to speed up the
determination of the address of the percpu variable. This is particularly
significant because these lookups occur in performance critical paths
of the core kernel. this_cpu_ptr() can avoid memory accesses and
this_cpu_ptr comes in two flavors. The preemption context matters since we
are referring the the currently executing processor. In many cases we must
insure that the processor does not change while a code segment is executed.
__this_cpu_ptr -> Do not check for preemption context
this_cpu_ptr -> Check preemption context
The parameter to these operations is a per cpu pointer. This can be the
address of a statically defined per cpu variable (&per_cpu_var(xxx)) or
the address of a per cpu variable allocated with the per cpu allocator.
per cpu atomic operations: this_cpu_*(var, val)
-----------------------------------------------
this_cpu_* operations (like this_cpu_add(struct->y, value) operate on
abitrary scalars that are members of structures allocated with the new
per cpu allocator. They can also operate on static per_cpu variables
if they are passed to per_cpu_var() (See patch to use this_cpu_*
operations for vm statistics).
These operations are guaranteed to be atomic vs preemption when modifying
the scalar. The calculation of the per cpu offset is also guaranteed to
be atomic at the same time. This means that a this_cpu_* operation can be
safely used to modify a per cpu variable in a context where interrupts are
enabled and preemption is allowed. Many architectures can perform such
a per cpu atomic operation with a single instruction.
Note that the atomicity here is different from regular atomic operations.
Atomicity is only guaranteed for data accessed from the currently executing
processor. Modifications from other processors are still possible. There
must be other guarantees that the per cpu data is not modified from another
processor when using these instruction. The per cpu atomicity is created
by the fact that the processor either executes and instruction or not.
Embedded in the instruction is the relocation of the per cpu address to
the are reserved for the current processor and the RMW action. Therefore
interrupts or preemption cannot occur in the mids of this processing.
Generic fallback functions are used if an arch does not define optimized
this_cpu operations. The functions come also come in the two flavors used
for this_cpu_ptr().
The firstparameter is a scalar that is a member of a structure allocated
through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The
operations are similar to what percpu_add() and friends do.
this_cpu_read(scalar)
this_cpu_write(scalar, value)
this_cpu_add(scale, value)
this_cpu_sub(scalar, value)
this_cpu_inc(scalar)
this_cpu_dec(scalar)
this_cpu_and(scalar, value)
this_cpu_or(scalar, value)
this_cpu_xor(scalar, value)
Arch code can override the generic functions and provide optimized atomic
per cpu operations. These atomic operations must provide both the relocation
(x86 does it through a segment override) and the operation on the data in a
single instruction. Otherwise preempt needs to be disabled and there is no
gain from providing arch implementations.
A third variant is provided prefixed by irqsafe_. These variants are safe
against hardware interrupts on the *same* processor (all per cpu atomic
primitives are *always* *only* providing safety for code running on the
*same* processor!). The increment needs to be implemented by the hardware
in such a way that it is a single RMW instruction that is either processed
before or after an interrupt.
cc: David Howells <dhowells@redhat.com>
cc: Ingo Molnar <mingo@elte.hu>
cc: Rusty Russell <rusty@rustcorp.com.au>
cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-03 18:48:22 +08:00
|
|
|
#endif
|
|
|
|
|
|
2005-04-17 06:20:36 +08:00
|
|
|
#endif /* __LINUX_PERCPU_H */
|