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Tejun Heo 490c79a657 percpu_ref: decouple switching to atomic mode and killing 
percpu_ref has treated the dropping of the base reference and
switching to atomic mode as an integral operation; however, there's
nothing inherent tying the two together.

The use cases for percpu_ref have been expanding continuously.  While
the current init/kill/reinit/exit model can cover a lot, the coupling
of kill/reinit with atomic/percpu mode switching is turning out to be
too restrictive for use cases where many percpu_refs are created and
destroyed back-to-back with only some of them reaching extended
operation.  The coupling also makes implementing always-atomic debug
mode difficult.

This patch separates out atomic mode switching into
percpu_ref_switch_to_atomic() and reimplements
percpu_ref_kill_and_confirm() on top of it.

* The handling of __PERCPU_REF_ATOMIC and __PERCPU_REF_DEAD is now
  differentiated.  Among get/put operations, percpu_ref_tryget_live()
  is the only one which cares about DEAD.

* percpu_ref_switch_to_atomic() can be called multiple times on the
  same ref.  This means that multiple @confirm_switch may get queued
  up which we can't do reliably without extra memory area.  This is
  handled by making the later invocation synchronously wait for the
  completion of the previous one.  This isn't particularly desirable
  but such synchronous waits shouldn't happen in most cases.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
 		2014-09-24 13:31:49 -04:00
..
fonts partly revert commit 8a10bc9: parisc/sti_console: prefer Linux fonts over built-in ROM fonts 2014-03-23 16:44:42 +01:00
lz4 lz4: add overrun checks to lz4_uncompress_unknownoutputsize() 2014-07-03 16:12:04 -07:00
lzo lzo: properly check for overruns 2014-06-23 14:12:01 -04:00
mpi MPILIB: add module description and license 2013-09-25 17:17:01 +01:00
raid6 md update for v3.12 2013-09-10 13:03:41 -07:00
reed_solomon
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xz lib/xz: enable all filters by default in Kconfig 2014-06-04 16:54:18 -07:00
zlib_deflate zlib: clean up some dead code 2014-08-06 18:01:24 -07:00
zlib_inflate zlib: clean up some dead code 2014-08-06 18:01:24 -07:00
.gitignore X.509: Implement simple static OID registry 2012-10-08 13:50:18 +10:30
Kconfig Make ARCH_HAS_FAST_MULTIPLIER a real config variable 2014-09-13 11:14:53 -07:00
Kconfig.debug lib: turn CONFIG_STACKTRACE into an actual option. 2014-08-29 16:28:16 -07:00
Kconfig.kgdb treewide: Fix typo in printk 2013-06-18 13:48:45 +02:00
Kconfig.kmemcheck
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Makefile lib: add lib/glob.c 2014-08-06 18:01:24 -07:00
argv_split.c argv_split(): teach it to handle mutable strings 2013-04-29 18:28:19 -07:00
asn1_decoder.c lib/asn1_decoder.c: kernel-doc warning fix 2014-06-04 16:54:19 -07:00
assoc_array.c KEYS: Fix termination condition in assoc array garbage collection 2014-09-12 22:34:31 +10:00
atomic64.c lib: atomic64: Initialize locks statically to fix early users 2012-12-20 13:50:16 -08:00
atomic64_test.c lib/atomic64_test.c: convert printk(KERN_INFO to pr_info 2014-06-04 16:54:19 -07:00
audit.c audit: Add generic compat syscall support 2014-03-20 10:11:35 -04:00
average.c lib: Ensure EWMA does not store wrong intermediate values 2014-01-16 23:46:06 -08:00
bcd.c usb/core: use bin2bcd() for bcdDevice in RH 2012-09-10 11:13:16 -07:00
bch.c lib: add shared BCH ECC library 2011-03-11 14:25:50 +00:00
bitmap.c lib: bitmap: add missing mask in bitmap_andnot 2014-08-06 18:01:27 -07:00
bitrev.c
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bsearch.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
btree.c lib/btree.c: fix leak of whole btree nodes 2014-06-04 16:54:18 -07:00
bug.c lib/bug.c: convert printk to pr_foo() 2014-06-04 16:54:19 -07:00
build_OID_registry X.509: do not emit any informational output 2013-06-19 17:54:06 +02:00
bust_spinlocks.c printk: Provide a wake_up_klogd() off-case 2013-03-22 16:41:20 -07:00
check_signature.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
checksum.c asm-generic headers: Allow yet more arch overrides in checksum.h 2013-02-11 20:00:33 +05:30
clz_ctz.c lib/clz_ctz.c: add prototype declarations in lib/clz_ctz.c 2014-04-03 16:21:12 -07:00
clz_tab.c lib: Fix multiple definitions of clz_tab 2012-02-02 10:34:23 +11:00
cmdline.c lib/cmdline.c: add size unit t/p/e to memparse 2014-08-06 18:01:25 -07:00
compat_audit.c audit: Add generic compat syscall support 2014-03-20 10:11:35 -04:00
cordic.c Docs: wording: functions -> algorithm 2011-10-29 21:20:22 +02:00
cpu-notifier-error-inject.c cpu: rewrite cpu-notifier-error-inject module 2012-07-30 17:25:22 -07:00
cpu_rmap.c Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
cpumask.c lib/cpumask: cpumask_set_cpu_local_first to use all cores when numa node is not defined 2014-07-02 18:29:23 -07:00
crc-ccitt.c
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crc-itu-t.c
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crc-t10dif.c crypto: crct10dif - Add fallback for broken initrds 2013-09-12 15:31:34 +10:00
crc7.c lib/crc7: Shift crc7() output left 1 bit 2014-05-16 14:26:52 -04:00
crc8.c lib: crc8: add new library module providing crc8 algorithm 2011-06-03 15:01:06 -04:00
crc16.c
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crc32.c lib: crc32: Add some additional __pure annotations 2014-06-25 16:04:00 -07:00
crc32defs.h crc32: select an algorithm via Kconfig 2012-03-23 16:58:38 -07:00
ctype.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
debug_locks.c mutex: Add support for wound/wait style locks 2013-06-26 12:10:56 +02:00
debugobjects.c lib/debugobjects.c: convert printk(KERN_DEBUG to pr_debug 2014-06-04 16:53:53 -07:00
dec_and_lock.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
decompress.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
decompress_bunzip2.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
decompress_inflate.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
decompress_unlz4.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
decompress_unlzma.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
decompress_unlzo.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
decompress_unxz.c initramfs: support initramfs that is bigger than 2GiB 2014-08-08 15:57:26 -07:00
devres.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-08-05 17:46:42 -07:00
digsig.c lib/digsig.c: kernel-doc warning fixes 2014-06-04 16:54:19 -07:00
div64.c math64: New separate div64_u64_rem helper 2013-08-23 09:02:14 -04:00
dma-debug.c dma debug: account for cachelines and read-only mappings in overlap tracking 2014-03-04 07:55:47 -08:00
dump_stack.c asmlinkage: Add explicit __visible to drivers/*, lib/*, kernel/* 2014-05-05 16:07:46 -07:00
dynamic_debug.c net: print net_device reg_state in netdev_* unless it's registered 2014-07-20 20:38:43 -07:00
dynamic_queue_limits.c bql: Avoid possible inconsistent calculation. 2012-05-31 18:18:17 -04:00
earlycpio.c earlycpio.c: Fix the confusing comment of find_cpio_data(). 2013-08-14 23:24:01 +02:00
extable.c
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fault-inject.c debugfs: add get/set for atomic types 2013-06-03 13:55:01 -07:00
fdt.c of/lib: Allow scripts/dtc/libfdt to be used from kernel code 2012-07-23 13:54:52 +01:00
fdt_empty_tree.c lib: add fdt_empty_tree.c 2014-04-30 19:49:37 +01:00
fdt_ro.c of/lib: Allow scripts/dtc/libfdt to be used from kernel code 2012-07-23 13:54:52 +01:00
fdt_rw.c of/lib: Allow scripts/dtc/libfdt to be used from kernel code 2012-07-23 13:54:52 +01:00
fdt_strerror.c of/lib: Allow scripts/dtc/libfdt to be used from kernel code 2012-07-23 13:54:52 +01:00
fdt_sw.c of/lib: Allow scripts/dtc/libfdt to be used from kernel code 2012-07-23 13:54:52 +01:00
fdt_wip.c of/lib: Allow scripts/dtc/libfdt to be used from kernel code 2012-07-23 13:54:52 +01:00
find_last_bit.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
find_next_bit.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
flex_array.c reciprocal_divide: update/correction of the algorithm 2014-01-21 23:17:20 -08:00
flex_proportions.c proportions: add @gfp to init functions 2014-09-08 09:51:30 +09:00
gcd.c lib/gcd.c: prevent possible div by 0 2012-10-06 03:04:57 +09:00
gen_crc32table.c sections: fix const sections for crc32 table 2012-10-06 03:04:46 +09:00
genalloc.c lib/genalloc.c: add check gen_pool_dma_alloc() if dma pointer is not NULL 2014-01-29 16:22:39 -08:00
glob.c lib/glob.c: add CONFIG_GLOB_SELFTEST 2014-08-06 18:01:25 -07:00
halfmd4.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
hash.c lib: hash: follow-up fixups for arch hash 2013-12-19 00:14:53 -05:00
hexdump.c lib: introduce upper case hex ascii helpers 2013-09-20 15:38:26 -04:00
hweight.c Make ARCH_HAS_FAST_MULTIPLIER a real config variable 2014-09-13 11:14:53 -07:00
idr.c lib/idr.c: fix out-of-bounds pointer dereference 2014-08-08 15:57:24 -07:00
inflate.c MN10300: Don't try and #include <linux/slab.h> in lib/inflate.c from bootloader 2010-08-12 09:51:35 -07:00
int_sqrt.c lib/int_sqrt.c: optimize square root algorithm 2013-04-29 18:28:19 -07:00
interval_tree.c lib: Export interval_tree 2014-05-05 09:09:14 +02:00
interval_tree_test.c lib: Export interval_tree 2014-05-05 09:09:14 +02:00
iomap.c Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
iomap_copy.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
iommu-helper.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
ioremap.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
iovec.c iovec: make sure the caller actually wants anything in memcpy_fromiovecend 2014-08-02 15:25:21 -07:00
irq_regs.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
is_single_threaded.c
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jedec_ddr_data.c ddr: add LPDDR2 data from JESD209-2 2012-05-02 00:04:06 -07:00
kasprintf.c lib/kasprintf.c: use kmalloc_track_caller() to get accurate traces for kvasprintf 2012-10-11 08:50:15 +09:00
kfifo.c kfifo: use BUG_ON 2014-08-08 15:57:25 -07:00
klist.c klist: use same naming scheme as hlist for klist_add_after() 2014-08-06 18:01:24 -07:00
kobject.c sysfs, kobject: add sysfs wrapper for kernfs_enable_ns() 2014-02-07 16:08:57 -08:00
kobject_uevent.c kobject: Make support for uevent_helper optional. 2014-04-25 12:00:49 -07:00
kstrtox.c lib/kstrtox.c: remove redundant cleanup 2014-01-23 16:36:57 -08:00
kstrtox.h lib/kstrtox: common code between kstrto*() and simple_strto*() functions 2011-10-31 17:30:56 -07:00
lcm.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
libcrc32c.c lib/libcrc32c.c: use PTR_ERR_OR_ZERO 2014-06-04 16:54:18 -07:00
list_debug.c rcu: Fix broken strings in RCU's source code. 2012-07-06 06:01:49 -07:00
list_sort.c lib/list_sort.c: convert to pr_foo 2014-08-06 18:01:25 -07:00
llist.c llists-move-llist_reverse_order-from-raid5-to-llistc-fix 2013-11-15 09:32:22 +09:00
locking-selftest-hardirq.h
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locking-selftest-mutex.h
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locking-selftest-rlock-hardirq.h
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locking-selftest-rlock-softirq.h
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locking-selftest-rlock.h
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locking-selftest-rsem.h
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locking-selftest-softirq.h
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locking-selftest-spin-hardirq.h
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locking-selftest-spin-softirq.h
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locking-selftest-spin.h
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locking-selftest-wlock-hardirq.h
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locking-selftest-wlock-softirq.h
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locking-selftest-wlock.h
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locking-selftest-wsem.h
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locking-selftest.c sched: Introduce preempt_count accessor functions 2013-09-25 14:07:32 +02:00
lockref.c arch, locking: Ciao arch_mutex_cpu_relax() 2014-07-17 12:32:47 +02:00
lru_cache.c drbd: debugfs: add per volume oldest_requests 2014-07-10 18:35:19 +02:00
md5.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
memory-notifier-error-inject.c memory: memory notifier error injection module 2012-07-30 17:25:22 -07:00
memweight.c string: introduce memweight() 2012-07-30 17:25:16 -07:00
net_utils.c mac_pton: Use bool not int return 2014-06-25 17:45:43 -07:00
nlattr.c Merge branch 'next' (accumulated 3.16 merge window patches) into master 2014-06-08 11:31:16 -07:00
notifier-error-inject.c mode_t, whack-a-mole at 11... 2013-04-09 14:13:05 -04:00
notifier-error-inject.h fault-injection: notifier error injection 2012-07-30 17:25:22 -07:00
of-reconfig-notifier-error-inject.c powerpc+of: Rename and fix OF reconfig notifier error inject module 2012-12-14 10:32:52 +11:00
oid_registry.c Give the OID registry file module info to avoid kernel tainting 2013-05-05 14:38:00 -07:00
parser.c lib/parser.c: put EXPORT_SYMBOLs in the conventional place 2014-01-23 16:36:55 -08:00
pci_iomap.c lib: add NO_GENERIC_PCI_IOPORT_MAP 2012-01-31 23:19:47 +02:00
percpu-refcount.c percpu_ref: decouple switching to atomic mode and killing 2014-09-24 13:31:49 -04:00
percpu_counter.c percpu_counter: add @gfp to percpu_counter_init() 2014-09-08 09:51:29 +09:00
percpu_ida.c Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2014-02-14 10:45:18 -08:00
percpu_test.c percpu: add test module for various percpu operations 2013-11-13 12:09:11 +09:00
plist.c lib/plist.c: replace pr_debug with printk in plist_test() 2014-06-04 16:54:18 -07:00
pm-notifier-error-inject.c PM: PM notifier error injection module 2012-07-30 17:25:22 -07:00
prio_heap.c
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proportions.c proportions: add @gfp to init functions 2014-09-08 09:51:30 +09:00
radix-tree.c lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations 2014-06-06 16:08:17 -07:00
random32.c random32: mix in entropy from core to late initcall 2014-07-30 13:55:27 -07:00
ratelimit.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
rational.c lib: Change mail address of Oskar Schirmer 2012-05-17 15:18:37 +02:00
rbtree.c lib/rbtree.c: fix typo in comment of __rb_insert() 2014-08-08 15:57:24 -07:00
rbtree_test.c rbtree/test: test rbtree_postorder_for_each_entry_safe() 2014-01-23 16:37:03 -08:00
reciprocal_div.c reciprocal_divide: update/correction of the algorithm 2014-01-21 23:17:20 -08:00
rhashtable.c lib: rhashtable: remove second linux/log2.h inclusion 2014-09-19 17:08:52 -04:00
scatterlist.c lib/scatterlist: make ARCH_HAS_SG_CHAIN an actual Kconfig 2014-08-08 15:57:26 -07:00
sha1.c lib: reduce the use of module.h wherever possible 2012-03-07 15:04:04 -05:00
show_mem.c lib/show_mem.c: show num_poisoned_pages when oom 2014-01-21 16:19:48 -08:00
smp_processor_id.c percpu: add preemption checks to __this_cpu ops 2014-04-07 16:36:14 -07:00
sort.c
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stmp_device.c lib: add support for stmp-style devices 2012-04-20 23:27:08 +02:00
string.c Make ARCH_HAS_FAST_MULTIPLIER a real config variable 2014-09-13 11:14:53 -07:00
string_helpers.c lib/string_helpers.c: constify static arrays 2014-08-06 18:01:25 -07:00
strncpy_from_user.c word-at-a-time: make the interfaces truly generic 2012-05-26 11:33:40 -07:00
strnlen_user.c lib: Fix generic strnlen_user for 32-bit big-endian machines 2012-05-27 20:59:46 -07:00
swiotlb.c swiotlb: don't assume PA 0 is invalid 2014-06-20 16:04:32 -04:00
syscall.c lib/syscall.c: unexport task_current_syscall() 2014-04-03 16:21:06 -07:00
test-kstrtox.c lib/test-kstrtox.c: use ARRAY_SIZE instead of sizeof/sizeof[0] 2014-08-06 18:01:25 -07:00
test-string_helpers.c lib/string_helpers: introduce generic string_unescape 2013-04-30 17:04:03 -07:00
test_bpf.c net: filter: split 'struct sk_filter' into socket and bpf parts 2014-08-02 15:03:58 -07:00
test_firmware.c test: add firmware_class loader test 2014-07-17 18:44:19 -07:00
test_module.c test: add minimal module for verification testing 2014-01-23 16:36:57 -08:00
test_user_copy.c test: check copy_to/from_user boundary validation 2014-01-23 16:36:57 -08:00
textsearch.c lib/textsearch.c: move EXPORT_SYMBOL after functions 2014-06-04 16:54:19 -07:00
timerqueue.c The following text was taken from the original review request: 2012-03-24 10:24:31 -07:00
ts_bm.c
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ts_fsm.c
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ts_kmp.c
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ucs2_string.c Move utf16 functions to kernel core and rename 2013-04-15 21:23:03 +01:00
usercopy.c Kconfig: consolidate CONFIG_DEBUG_STRICT_USER_COPY_CHECKS 2013-04-30 17:04:09 -07:00
uuid.c uuid: use prandom_bytes() 2013-04-29 18:28:42 -07:00
vsprintf.c lib/vsprintf.c: fix comparison to bool 2014-06-04 16:54:18 -07:00