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Author SHA1 Message Date
Mel Gorman 0e9f02450d sched/fair: Do not re-read ->h_load_next during hierarchical load calculation 
A NULL pointer dereference bug was reported on a distribution kernel but
the same issue should be present on mainline kernel. It occured on s390
but should not be arch-specific.  A partial oops looks like:

  Unable to handle kernel pointer dereference in virtual kernel address space
  ...
  Call Trace:
    ...
    try_to_wake_up+0xfc/0x450
    vhost_poll_wakeup+0x3a/0x50 [vhost]
    __wake_up_common+0xbc/0x178
    __wake_up_common_lock+0x9e/0x160
    __wake_up_sync_key+0x4e/0x60
    sock_def_readable+0x5e/0x98

The bug hits any time between 1 hour to 3 days. The dereference occurs
in update_cfs_rq_h_load when accumulating h_load. The problem is that
cfq_rq->h_load_next is not protected by any locking and can be updated
by parallel calls to task_h_load. Depending on the compiler, code may be
generated that re-reads cfq_rq->h_load_next after the check for NULL and
then oops when reading se->avg.load_avg. The dissassembly showed that it
was possible to reread h_load_next after the check for NULL.

While this does not appear to be an issue for later compilers, it's still
an accident if the correct code is generated. Full locking in this path
would have high overhead so this patch uses READ_ONCE to read h_load_next
only once and check for NULL before dereferencing. It was confirmed that
there were no further oops after 10 days of testing.

As Peter pointed out, it is also necessary to use WRITE_ONCE() to avoid any
potential problems with store tearing.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Fixes: 685207963b ("sched: Move h_load calculation to task_h_load()")
Link: https://lkml.kernel.org/r/20190319123610.nsivgf3mjbjjesxb@techsingularity.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-04-03 09:50:22 +02:00
Linus Torvalds 231c807a60 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull scheduler updates from Thomas Gleixner:
 "Third more careful attempt for this set of fixes:

   - Prevent a 32bit math overflow in the cpufreq code

   - Fix a buffer overflow when scanning the cgroup2 cpu.max property

   - A set of fixes for the NOHZ scheduler logic to prevent waking up
     CPUs even if the capacity of the busy CPUs is sufficient along with
     other tweaks optimizing the behaviour for asymmetric systems
     (big/little)"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Skip LLC NOHZ logic for asymmetric systems
  sched/fair: Tune down misfit NOHZ kicks
  sched/fair: Comment some nohz_balancer_kick() kick conditions
  sched/core: Fix buffer overflow in cgroup2 property cpu.max
  sched/cpufreq: Fix 32-bit math overflow
 2019-03-24 11:42:10 -07:00
Valentin Schneider b9a7b88316 sched/fair: Skip LLC NOHZ logic for asymmetric systems 
The LLC NOHZ condition will become true as soon as >=2 CPUs in a
single LLC domain are busy. On big.LITTLE systems, this translates to
two or more CPUs of a "cluster" (big or LITTLE) being busy.

Issuing a NOHZ kick in these conditions isn't desired for asymmetric
systems, as if the busy CPUs can provide enough compute capacity to
the running tasks, then we can leave the NOHZ CPUs in peace.

Skip the LLC NOHZ condition for asymmetric systems, and rely on
nr_running & capacity checks to trigger NOHZ kicks when the system
actually needs them.

Suggested-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dietmar.Eggemann@arm.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190211175946.4961-4-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-03-19 12:06:15 +01:00
Valentin Schneider a0fe2cf086 sched/fair: Tune down misfit NOHZ kicks 
In this commit:

  3b1baa6496 ("sched/fair: Add 'group_misfit_task' load-balance type")

we set rq->misfit_task_load whenever the current running task has a
utilization greater than 80% of rq->cpu_capacity. A non-zero value in
this field enables misfit load balancing.

However, if the task being looked at is already running on a CPU of
highest capacity, there's nothing more we can do for it. We can
currently spot this in update_sd_pick_busiest(), which prevents us
from selecting a sched_group of group_type == group_misfit_task as the
busiest group, but we don't do any of that in nohz_balancer_kick().

This means that we could repeatedly kick NOHZ CPUs when there's no
improvements in terms of load balance to be done.

Introduce a check_misfit_status() helper that returns true iff there
is a CPU in the system that could give more CPU capacity to a rq's
misfit task - IOW, there exists a CPU of higher capacity_orig or the
rq's CPU is severely pressured by rt/IRQ.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dietmar.Eggemann@arm.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190211175946.4961-3-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-03-19 12:06:15 +01:00
Valentin Schneider e25a7a944f sched/fair: Comment some nohz_balancer_kick() kick conditions 
We now have a comment explaining the first sched_domain based NOHZ kick,
so might as well comment them all.

While at it, unwrap a line that fits under 80 characters.

Co-authored-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dietmar.Eggemann@arm.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190211175946.4961-2-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-03-19 12:06:15 +01:00
Konstantin Khlebnikov 4c47acd824 sched/core: Fix buffer overflow in cgroup2 property cpu.max 
Add limit into sscanf format string for on-stack buffer.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 0d5936344f ("sched: Implement interface for cgroup unified hierarchy")
Link: https://lkml.kernel.org/r/155189230232.2620.13120481613524200065.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-03-19 12:06:15 +01:00
Peter Zijlstra a23314e9d8 sched/cpufreq: Fix 32-bit math overflow 
Vincent Wang reported that get_next_freq() has a mult overflow bug on
32-bit platforms in the IOWAIT boost case, since in that case {util,max}
are in freq units instead of capacity units.

Solve this by moving the IOWAIT boost to capacity units. And since this
means @max is constant; simplify the code.

Reported-by: Vincent Wang <vincent.wang@unisoc.com>
Tested-by: Vincent Wang <vincent.wang@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190305083202.GU32494@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-03-19 12:06:11 +01:00
Linus Torvalds 8dcd175bc3 Merge branch 'akpm' (patches from Andrew) 
Merge misc updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (159 commits)
  tools/testing/selftests/proc/proc-self-syscall.c: remove duplicate include
  proc: more robust bulk read test
  proc: test /proc/*/maps, smaps, smaps_rollup, statm
  proc: use seq_puts() everywhere
  proc: read kernel cpu stat pointer once
  proc: remove unused argument in proc_pid_lookup()
  fs/proc/thread_self.c: code cleanup for proc_setup_thread_self()
  fs/proc/self.c: code cleanup for proc_setup_self()
  proc: return exit code 4 for skipped tests
  mm,mremap: bail out earlier in mremap_to under map pressure
  mm/sparse: fix a bad comparison
  mm/memory.c: do_fault: avoid usage of stale vm_area_struct
  writeback: fix inode cgroup switching comment
  mm/huge_memory.c: fix "orig_pud" set but not used
  mm/hotplug: fix an imbalance with DEBUG_PAGEALLOC
  mm/memcontrol.c: fix bad line in comment
  mm/cma.c: cma_declare_contiguous: correct err handling
  mm/page_ext.c: fix an imbalance with kmemleak
  mm/compaction: pass pgdat to too_many_isolated() instead of zone
  mm: remove zone_lru_lock() function, access ->lru_lock directly
  ...
 2019-03-06 10:31:36 -08:00
Linus Torvalds 45802da05e Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle were:

   - refcount conversions

   - Solve the rq->leaf_cfs_rq_list can of worms for real.

   - improve power-aware scheduling

   - add sysctl knob for Energy Aware Scheduling

   - documentation updates

   - misc other changes"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
  kthread: Do not use TIMER_IRQSAFE
  kthread: Convert worker lock to raw spinlock
  sched/fair: Use non-atomic cpumask_{set,clear}_cpu()
  sched/fair: Remove unused 'sd' parameter from select_idle_smt()
  sched/wait: Use freezable_schedule() when possible
  sched/fair: Prune, fix and simplify the nohz_balancer_kick() comment block
  sched/fair: Explain LLC nohz kick condition
  sched/fair: Simplify nohz_balancer_kick()
  sched/topology: Fix percpu data types in struct sd_data & struct s_data
  sched/fair: Simplify post_init_entity_util_avg() by calling it with a task_struct pointer argument
  sched/fair: Fix O(nr_cgroups) in the load balancing path
  sched/fair: Optimize update_blocked_averages()
  sched/fair: Fix insertion in rq->leaf_cfs_rq_list
  sched/fair: Add tmp_alone_branch assertion
  sched/core: Use READ_ONCE()/WRITE_ONCE() in move_queued_task()/task_rq_lock()
  sched/debug: Initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK
  sched/pelt: Skip updating util_est when utilization is higher than CPU's capacity
  sched/fair: Update scale invariance of PELT
  sched/fair: Move the rq_of() helper function
  sched/core: Convert task_struct.stack_refcount to refcount_t
  ...
 2019-03-06 08:14:05 -08:00
Linus Torvalds 3478588b51 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull locking updates from Ingo Molnar:
 "The biggest part of this tree is the new auto-generated atomics API
  wrappers by Mark Rutland.

  The primary motivation was to allow instrumentation without uglifying
  the primary source code.

  The linecount increase comes from adding the auto-generated files to
  the Git space as well:

    include/asm-generic/atomic-instrumented.h     | 1689 ++++++++++++++++--
    include/asm-generic/atomic-long.h             | 1174 ++++++++++---
    include/linux/atomic-fallback.h               | 2295 +++++++++++++++++++++++++
    include/linux/atomic.h                        | 1241 +------------

  I preferred this approach, so that the full call stack of the (already
  complex) locking APIs is still fully visible in 'git grep'.

  But if this is excessive we could certainly hide them.

  There's a separate build-time mechanism to determine whether the
  headers are out of date (they should never be stale if we do our job
  right).

  Anyway, nothing from this should be visible to regular kernel
  developers.

  Other changes:

   - Add support for dynamic keys, which removes a source of false
     positives in the workqueue code, among other things (Bart Van
     Assche)

   - Updates to tools/memory-model (Andrea Parri, Paul E. McKenney)

   - qspinlock, wake_q and lockdep micro-optimizations (Waiman Long)

   - misc other updates and enhancements"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (48 commits)
  locking/lockdep: Shrink struct lock_class_key
  locking/lockdep: Add module_param to enable consistency checks
  lockdep/lib/tests: Test dynamic key registration
  lockdep/lib/tests: Fix run_tests.sh
  kernel/workqueue: Use dynamic lockdep keys for workqueues
  locking/lockdep: Add support for dynamic keys
  locking/lockdep: Verify whether lock objects are small enough to be used as class keys
  locking/lockdep: Check data structure consistency
  locking/lockdep: Reuse lock chains that have been freed
  locking/lockdep: Fix a comment in add_chain_cache()
  locking/lockdep: Introduce lockdep_next_lockchain() and lock_chain_count()
  locking/lockdep: Reuse list entries that are no longer in use
  locking/lockdep: Free lock classes that are no longer in use
  locking/lockdep: Update two outdated comments
  locking/lockdep: Make it easy to detect whether or not inside a selftest
  locking/lockdep: Split lockdep_free_key_range() and lockdep_reset_lock()
  locking/lockdep: Initialize the locks_before and locks_after lists earlier
  locking/lockdep: Make zap_class() remove all matching lock order entries
  locking/lockdep: Reorder struct lock_class members
  locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache
  ...
 2019-03-06 07:17:17 -08:00
Mel Gorman 5e1f0f098b mm, compaction: capture a page under direct compaction 
Compaction is inherently race-prone as a suitable page freed during
compaction can be allocated by any parallel task.  This patch uses a
capture_control structure to isolate a page immediately when it is freed
by a direct compactor in the slow path of the page allocator.  The
intent is to avoid redundant scanning.

                                     5.0.0-rc1              5.0.0-rc1
                               selective-v3r17          capture-v3r19
Amean     fault-both-1         0.00 (   0.00%)        0.00 *   0.00%*
Amean     fault-both-3      2582.11 (   0.00%)     2563.68 (   0.71%)
Amean     fault-both-5      4500.26 (   0.00%)     4233.52 (   5.93%)
Amean     fault-both-7      5819.53 (   0.00%)     6333.65 (  -8.83%)
Amean     fault-both-12     9321.18 (   0.00%)     9759.38 (  -4.70%)
Amean     fault-both-18     9782.76 (   0.00%)    10338.76 (  -5.68%)
Amean     fault-both-24    15272.81 (   0.00%)    13379.55 *  12.40%*
Amean     fault-both-30    15121.34 (   0.00%)    16158.25 (  -6.86%)
Amean     fault-both-32    18466.67 (   0.00%)    18971.21 (  -2.73%)

Latency is only moderately affected but the devil is in the details.  A
closer examination indicates that base page fault latency is reduced but
latency of huge pages is increased as it takes creater care to succeed.
Part of the "problem" is that allocation success rates are close to 100%
even when under pressure and compaction gets harder

                                5.0.0-rc1              5.0.0-rc1
                          selective-v3r17          capture-v3r19
Percentage huge-3        96.70 (   0.00%)       98.23 (   1.58%)
Percentage huge-5        96.99 (   0.00%)       95.30 (  -1.75%)
Percentage huge-7        94.19 (   0.00%)       97.24 (   3.24%)
Percentage huge-12       94.95 (   0.00%)       97.35 (   2.53%)
Percentage huge-18       96.74 (   0.00%)       97.30 (   0.58%)
Percentage huge-24       97.07 (   0.00%)       97.55 (   0.50%)
Percentage huge-30       95.69 (   0.00%)       98.50 (   2.95%)
Percentage huge-32       96.70 (   0.00%)       99.27 (   2.65%)

And scan rates are reduced as expected by 6% for the migration scanner
and 29% for the free scanner indicating that there is less redundant
work.

Compaction migrate scanned    20815362    19573286
Compaction free scanned       16352612    11510663

[mgorman@techsingularity.net: remove redundant check]
  Link: http://lkml.kernel.org/r/20190201143853.GH9565@techsingularity.net
Link: http://lkml.kernel.org/r/20190118175136.31341-23-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2019-03-05 21:07:17 -08:00
Anshuman Khandual 98fa15f34c mm: replace all open encodings for NUMA_NO_NODE 
Patch series "Replace all open encodings for NUMA_NO_NODE", v3.

All these places for replacement were found by running the following
grep patterns on the entire kernel code.  Please let me know if this
might have missed some instances.  This might also have replaced some
false positives.  I will appreciate suggestions, inputs and review.

1. git grep "nid == -1"
2. git grep "node == -1"
3. git grep "nid = -1"
4. git grep "node = -1"

This patch (of 2):

At present there are multiple places where invalid node number is
encoded as -1.  Even though implicitly understood it is always better to
have macros in there.  Replace these open encodings for an invalid node
number with the global macro NUMA_NO_NODE.  This helps remove NUMA
related assumptions like 'invalid node' from various places redirecting
them to a common definition.

Link: http://lkml.kernel.org/r/1545127933-10711-2-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>	[ixgbe]
Acked-by: Jens Axboe <axboe@kernel.dk>			[mtip32xx]
Acked-by: Vinod Koul <vkoul@kernel.org>			[dmaengine.c]
Acked-by: Michael Ellerman <mpe@ellerman.id.au>		[powerpc]
Acked-by: Doug Ledford <dledford@redhat.com>		[drivers/infiniband]
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2019-03-05 21:07:14 -08:00
Linus Torvalds 3717f613f4 Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull RCU updates from Ingo Molnar:
 "The main RCU related changes in this cycle were:

   - Additional cleanups after RCU flavor consolidation

   - Grace-period forward-progress cleanups and improvements

   - Documentation updates

   - Miscellaneous fixes

   - spin_is_locked() conversions to lockdep

   - SPDX changes to RCU source and header files

   - SRCU updates

   - Torture-test updates, including nolibc updates and moving nolibc to
     tools/include"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits)
  locking/locktorture: Convert to SPDX license identifier
  linux/torture: Convert to SPDX license identifier
  torture: Convert to SPDX license identifier
  linux/srcu: Convert to SPDX license identifier
  linux/rcutree: Convert to SPDX license identifier
  linux/rcutiny: Convert to SPDX license identifier
  linux/rcu_sync: Convert to SPDX license identifier
  linux/rcu_segcblist: Convert to SPDX license identifier
  linux/rcupdate: Convert to SPDX license identifier
  linux/rcu_node_tree: Convert to SPDX license identifier
  rcu/update: Convert to SPDX license identifier
  rcu/tree: Convert to SPDX license identifier
  rcu/tiny: Convert to SPDX license identifier
  rcu/sync: Convert to SPDX license identifier
  rcu/srcu: Convert to SPDX license identifier
  rcu/rcutorture: Convert to SPDX license identifier
  rcu/rcu_segcblist: Convert to SPDX license identifier
  rcu/rcuperf: Convert to SPDX license identifier
  rcu/rcu.h: Convert to SPDX license identifier
  RCU/torture.txt: Remove section MODULE PARAMETERS
  ...
 2019-03-05 14:49:11 -08:00
Linus Torvalds b1b988a6a0 Merge branch 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull year 2038 updates from Thomas Gleixner:
 "Another round of changes to make the kernel ready for 2038. After lots
  of preparatory work this is the first set of syscalls which are 2038
  safe:

    403 clock_gettime64
    404 clock_settime64
    405 clock_adjtime64
    406 clock_getres_time64
    407 clock_nanosleep_time64
    408 timer_gettime64
    409 timer_settime64
    410 timerfd_gettime64
    411 timerfd_settime64
    412 utimensat_time64
    413 pselect6_time64
    414 ppoll_time64
    416 io_pgetevents_time64
    417 recvmmsg_time64
    418 mq_timedsend_time64
    419 mq_timedreceiv_time64
    420 semtimedop_time64
    421 rt_sigtimedwait_time64
    422 futex_time64
    423 sched_rr_get_interval_time64

  The syscall numbers are identical all over the architectures"

* 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  riscv: Use latest system call ABI
  checksyscalls: fix up mq_timedreceive and stat exceptions
  unicore32: Fix __ARCH_WANT_STAT64 definition
  asm-generic: Make time32 syscall numbers optional
  asm-generic: Drop getrlimit and setrlimit syscalls from default list
  32-bit userspace ABI: introduce ARCH_32BIT_OFF_T config option
  compat ABI: use non-compat openat and open_by_handle_at variants
  y2038: add 64-bit time_t syscalls to all 32-bit architectures
  y2038: rename old time and utime syscalls
  y2038: remove struct definition redirects
  y2038: use time32 syscall names on 32-bit
  syscalls: remove obsolete __IGNORE_ macros
  y2038: syscalls: rename y2038 compat syscalls
  x86/x32: use time64 versions of sigtimedwait and recvmmsg
  timex: change syscalls to use struct __kernel_timex
  timex: use __kernel_timex internally
  sparc64: add custom adjtimex/clock_adjtime functions
  time: fix sys_timer_settime prototype
  time: Add struct __kernel_timex
  time: make adjtime compat handling available for 32 bit
  ...
 2019-03-05 14:08:26 -08:00
David S. Miller f7fb7c1a1c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 
Daniel Borkmann says:

====================
pull-request: bpf-next 2019-03-04

The following pull-request contains BPF updates for your *net-next* tree.

The main changes are:

1) Add AF_XDP support to libbpf. Rationale is to facilitate writing
   AF_XDP applications by offering higher-level APIs that hide many
   of the details of the AF_XDP uapi. Sample programs are converted
   over to this new interface as well, from Magnus.

2) Introduce a new cant_sleep() macro for annotation of functions
   that cannot sleep and use it in BPF_PROG_RUN() to assert that
   BPF programs run under preemption disabled context, from Peter.

3) Introduce per BPF prog stats in order to monitor the usage
   of BPF; this is controlled by kernel.bpf_stats_enabled sysctl
   knob where monitoring tools can make use of this to efficiently
   determine the average cost of programs, from Alexei.

4) Split up BPF selftest's test_progs similarly as we already
   did with test_verifier. This allows to further reduce merge
   conflicts in future and to get more structure into our
   quickly growing BPF selftest suite, from Stanislav.

5) Fix a bug in BTF's dedup algorithm which can cause an infinite
   loop in some circumstances; also various BPF doc fixes and
   improvements, from Andrii.

6) Various BPF sample cleanups and migration to libbpf in order
   to further isolate the old sample loader code (so we can get
   rid of it at some point), from Jakub.

7) Add a new BPF helper for BPF cgroup skb progs that allows
   to set ECN CE code point and a Host Bandwidth Manager (HBM)
   sample program for limiting the bandwidth used by v2 cgroups,
   from Lawrence.

8) Enable write access to skb->queue_mapping from tc BPF egress
   programs in order to let BPF pick TX queue, from Jesper.

9) Fix a bug in BPF spinlock handling for map-in-map which did
   not propagate spin_lock_off to the meta map, from Yonghong.

10) Fix a bug in the new per-CPU BPF prog counters to properly
    initialize stats for each CPU, from Eric.

11) Add various BPF helper prototypes to selftest's bpf_helpers.h,
    from Willem.

12) Fix various BPF samples bugs in XDP and tracing progs,
    from Toke, Daniel and Yonghong.

13) Silence preemption splat in test_bpf after BPF_PROG_RUN()
    enforces it now everywhere, from Anders.

14) Fix a signedness bug in libbpf's btf_dedup_ref_type() to
    get error handling working, from Dan.

15) Fix bpftool documentation and auto-completion with regards
    to stream_{verdict,parser} attach types, from Alban.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
 2019-03-04 10:14:31 -08:00
Ingo Molnar 0614621d89 Merge branch 'linus' into locking/core, to pick up fixes 
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-28 07:50:39 +01:00
Johannes Weiner 4e37504d1c psi: avoid divide-by-zero crash inside virtual machines 
We've been seeing hard-to-trigger psi crashes when running inside VM
instances:

    divide error: 0000 [#1] SMP PTI
    Modules linked in: [...]
    CPU: 0 PID: 212 Comm: kworker/0:2 Not tainted 4.16.18-119_fbk9_3817_gfe944c98d695 #119
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
    Workqueue: events psi_clock
    RIP: 0010:psi_update_stats+0x270/0x490
    RSP: 0018:ffffc90001117e10 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8800a35a13f8
    RDX: 0000000000000000 RSI: ffff8800a35a1340 RDI: 0000000000000000
    RBP: 0000000000000658 R08: ffff8800a35a1470 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
    R13: 0000000000000000 R14: 0000000000000000 R15: 00000000000f8502
    FS:  0000000000000000(0000) GS:ffff88023fc00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007fbe370fa000 CR3: 00000000b1e3a000 CR4: 00000000000006f0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     psi_clock+0x12/0x50
     process_one_work+0x1e0/0x390
     worker_thread+0x2b/0x3c0
     ? rescuer_thread+0x330/0x330
     kthread+0x113/0x130
     ? kthread_create_worker_on_cpu+0x40/0x40
     ? SyS_exit_group+0x10/0x10
     ret_from_fork+0x35/0x40
    Code: 48 0f 47 c7 48 01 c2 45 85 e4 48 89 16 0f 85 e6 00 00 00 4c 8b 49 10 4c 8b 51 08 49 69 d9 f2 07 00 00 48 6b c0 64 4c 8b 29 31 d2 <48> f7 f7 49 69 d5 8d 06 00 00 48 89 c5 4c 69 f0 00 98 0b 00 48

The Code-line points to `period` being 0 inside update_stats(), and we
divide by that when calculating that period's pressure percentage.

The elapsed period should never be 0.  The reason this can happen is due
to an off-by-one in the idle time / missing period calculation combined
with a coarse sched_clock() in the virtual machine.

The target time for aggregation is advanced into the future on a fixed
grid to prevent clock drift.  So when an aggregation runs after some idle
period, we can not just set it to "now + psi_period", but have to
calculate the downtime and advance the target time relative to itself.

However, if the aggregator was disabled exactly one psi_period (ns), we
drop one idle period in the calculation due to a > when we should do >=.
In that case, next_update will be advanced from 'now - psi_period' to
'now' when it should be moved to 'now + psi_period'.  The run finishes
with last_update == next_update == sched_clock().

With hardware clocks, this exact nanosecond match isn't likely in the
first place; but if it does happen, the clock will still have moved on and
the period non-zero by the time the worker runs.  A pointlessly short
period, but besides the extra work, no harm no foul.  However, a slow
sched_clock() like we have on VMs might not have advanced either by the
time the worker runs again.  And when we calculate the elapsed period, the
result, our pressure divisor, will be 0.  Ouch.

Fix this by correctly handling the situation when the elapsed time between
aggregation runs is precisely two periods, and advance the expiration
timestamp correctly to period into the future.

Link: http://lkml.kernel.org/r/20190214193157.15788-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Łukasz Siudut <lsiudut@fb.com
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2019-02-21 09:01:00 -08:00
Peter Zijlstra 568f196756 bpf: check that BPF programs run with preemption disabled 
Introduce cant_sleep() macro for annotation of functions that
cannot sleep.

Use it in BPF_PROG_RUN to catch execution of BPF programs in
preemptable context.

Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
 2019-02-19 21:53:07 +01:00
Ingo Molnar cae45e1c6c Merge branch 'rcu-next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu 
Pull the latest RCU tree from Paul E. McKenney:

 - Additional cleanups after RCU flavor consolidation
 - Grace-period forward-progress cleanups and improvements
 - Documentation updates
 - Miscellaneous fixes
 - spin_is_locked() conversions to lockdep
 - SPDX changes to RCU source and header files
 - SRCU updates
 - Torture-test updates, including nolibc updates and moving
   nolibc to tools/include

Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-13 08:36:18 +01:00
Viresh Kumar c89d92eddf sched/fair: Use non-atomic cpumask_{set,clear}_cpu() 
The cpumasks updated here are not subject to concurrency and using
atomic bitops for them is pointless and expensive. Use the non-atomic
variants instead.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/2e2a10f84b9049a81eef94ed6d5989447c21e34a.1549963617.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-13 08:34:13 +01:00
Viresh Kumar 1b5500d734 sched/fair: Remove unused 'sd' parameter from select_idle_smt() 
The 'sd' parameter isn't getting used in select_idle_smt(), drop it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/f91c5e118183e79d4a982e9ac4ce5e47948f6c1b.1549536337.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:48:27 +01:00
Valentin Schneider 9f132742d5 sched/fair: Prune, fix and simplify the nohz_balancer_kick() comment block 
The comment block for that function lists the heuristics for
triggering a nohz kick, but the most recent ones (blocked load
updates, misfit) aren't included, and some of them (LLC nohz logic,
asym packing) are no longer in sync with the code.

The conditions are either simple enough or properly commented, so get
rid of that list instead of letting it grow.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190117153411.2390-4-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:18 +01:00
Valentin Schneider 892d59c222 sched/fair: Explain LLC nohz kick condition 
Provide a comment explaining the LLC related nohz kick in
nohz_balancer_kick().

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190117153411.2390-3-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:17 +01:00
Valentin Schneider 7edab78d74 sched/fair: Simplify nohz_balancer_kick() 
Calling 'nohz_balance_exit_idle(rq)' will always clear 'rq->cpu' from
'nohz.idle_cpus_mask' if it is set. Since it is called at the top of
'nohz_balancer_kick()', 'rq->cpu' will never be set in
'nohz.idle_cpus_mask' if it is accessed in the rest of the function.

Combine the 'sched_domain_span()' with 'nohz.idle_cpus_mask' and drop the
'(i == cpu)' check since 'rq->cpu' will never be iterated over.

While at it, clean up a condition alignment.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: morten.rasmussen@arm.com
Cc: vincent.guittot@linaro.org
Link: https://lkml.kernel.org/r/20190117153411.2390-2-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:16 +01:00
Luc Van Oostenryck 99687cdbb3 sched/topology: Fix percpu data types in struct sd_data & struct s_data 
The percpu members of struct sd_data and s_data are declared as:

	struct ... ** __percpu member;

So their type is:

	__percpu pointer to pointer to struct ...

But looking at how they're used, their type should be:

	pointer to __percpu pointer to struct ...

and they should thus be declared as:

	struct ... * __percpu *member;

So fix the placement of '__percpu' in the definition of these
structures.

This addresses a bunch of Sparse's warnings like:

	warning: incorrect type in initializer (different address spaces)
	  expected void const [noderef] <asn:3> *__vpp_verify
	  got struct sched_domain **

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190118144936.79158-1-luc.vanoostenryck@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:15 +01:00
Dietmar Eggemann d0fe0b9c45 sched/fair: Simplify post_init_entity_util_avg() by calling it with a task_struct pointer argument 
Since commit:

  d03266910a ("sched/fair: Fix task group initialization")

the utilization of a sched entity representing a task group is no longer
initialized to any other value than 0. So post_init_entity_util_avg() is
only used for tasks, not for sched_entities.

Make this clear by calling it with a task_struct pointer argument which
also eliminates the entity_is_task(se) if condition in the fork path and
get rid of the stale comment in remove_entity_load_avg() accordingly.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20190122162501.12000-1-dietmar.eggemann@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:14 +01:00
Vincent Guittot 039ae8bcf7 sched/fair: Fix O(nr_cgroups) in the load balancing path 
This re-applies the commit reverted here:

  commit c40f7d74c7 ("sched/fair: Fix infinite loop in update_blocked_averages() by reverting a9e7f6544b9c")

I.e. now that cfs_rq can be safely removed/added in the list, we can re-apply:

 commit a9e7f6544b ("sched/fair: Fix O(nr_cgroups) in load balance path")

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: sargun@sargun.me
Cc: tj@kernel.org
Cc: xiexiuqi@huawei.com
Cc: xiezhipeng1@huawei.com
Link: https://lkml.kernel.org/r/1549469662-13614-3-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:13 +01:00
Vincent Guittot 31bc6aeaab sched/fair: Optimize update_blocked_averages() 
Removing a cfs_rq from rq->leaf_cfs_rq_list can break the parent/child
ordering of the list when it will be added back. In order to remove an
empty and fully decayed cfs_rq, we must remove its children too, so they
will be added back in the right order next time.

With a normal decay of PELT, a parent will be empty and fully decayed
if all children are empty and fully decayed too. In such a case, we just
have to ensure that the whole branch will be added when a new task is
enqueued. This is default behavior since :

  commit f678331973 ("sched/fair: Fix insertion in rq->leaf_cfs_rq_list")

In case of throttling, the PELT of throttled cfs_rq will not be updated
whereas the parent will. This breaks the assumption made above unless we
remove the children of a cfs_rq that is throttled. Then, they will be
added back when unthrottled and a sched_entity will be enqueued.

As throttled cfs_rq are now removed from the list, we can remove the
associated test in update_blocked_averages().

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: sargun@sargun.me
Cc: tj@kernel.org
Cc: xiexiuqi@huawei.com
Cc: xiezhipeng1@huawei.com
Link: https://lkml.kernel.org/r/1549469662-13614-2-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:02:12 +01:00
Ingo Molnar c9ba7560c5 Linux 5.0-rc6 
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Merge tag 'v5.0-rc6' into sched/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-11 08:01:50 +01:00
Thomas Gleixner 41ea39101d y2038: Add time64 system calls 
This series finally gets us to the point of having system calls with
 64-bit time_t on all architectures, after a long time of incremental
 preparation patches.
 
 There was actually one conversion that I missed during the summer,
 i.e. Deepa's timex series, which I now updated based the 5.0-rc1 changes
 and review comments.
 
 The following system calls are now added on all 32-bit architectures
 using the same system call numbers:
 
 403 clock_gettime64
 404 clock_settime64
 405 clock_adjtime64
 406 clock_getres_time64
 407 clock_nanosleep_time64
 408 timer_gettime64
 409 timer_settime64
 410 timerfd_gettime64
 411 timerfd_settime64
 412 utimensat_time64
 413 pselect6_time64
 414 ppoll_time64
 416 io_pgetevents_time64
 417 recvmmsg_time64
 418 mq_timedsend_time64
 419 mq_timedreceiv_time64
 420 semtimedop_time64
 421 rt_sigtimedwait_time64
 422 futex_time64
 423 sched_rr_get_interval_time64
 
 Each one of these corresponds directly to an existing system call
 that includes a 'struct timespec' argument, or a structure containing
 a timespec or (in case of clock_adjtime) timeval. Not included here
 are new versions of getitimer/setitimer and getrusage/waitid, which
 are planned for the future but only needed to make a consistent API
 rather than for correct operation beyond y2038. These four system
 calls are based on 'timeval', and it has not been finally decided
 what the replacement kernel interface will use instead.
 
 So far, I have done a lot of build testing across most architectures,
 which has found a number of bugs. Runtime testing so far included
 testing LTP on 32-bit ARM with the existing system calls, to ensure
 we do not regress for existing binaries, and a test with a 32-bit
 x86 build of LTP against a modified version of the musl C library
 that has been adapted to the new system call interface [3].
 This library can be used for testing on all architectures supported
 by musl-1.1.21, but it is not how the support is getting integrated
 into the official musl release. Official musl support is planned
 but will require more invasive changes to the library.
 
 Link: https://lore.kernel.org/lkml/20190110162435.309262-1-arnd@arndb.de/T/
 Link: https://lore.kernel.org/lkml/20190118161835.2259170-1-arnd@arndb.de/
 Link: https://git.linaro.org/people/arnd/musl-y2038.git/ [2]
 Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Merge tag 'y2038-new-syscalls' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground into timers/2038

Pull y2038 - time64 system calls from Arnd Bergmann:

This series finally gets us to the point of having system calls with 64-bit
time_t on all architectures, after a long time of incremental preparation
patches.

There was actually one conversion that I missed during the summer,
i.e. Deepa's timex series, which I now updated based the 5.0-rc1 changes
and review comments.

The following system calls are now added on all 32-bit architectures using
the same system call numbers:

403 clock_gettime64
404 clock_settime64
405 clock_adjtime64
406 clock_getres_time64
407 clock_nanosleep_time64
408 timer_gettime64
409 timer_settime64
410 timerfd_gettime64
411 timerfd_settime64
412 utimensat_time64
413 pselect6_time64
414 ppoll_time64
416 io_pgetevents_time64
417 recvmmsg_time64
418 mq_timedsend_time64
419 mq_timedreceiv_time64
420 semtimedop_time64
421 rt_sigtimedwait_time64
422 futex_time64
423 sched_rr_get_interval_time64

Each one of these corresponds directly to an existing system call that
includes a 'struct timespec' argument, or a structure containing a timespec
or (in case of clock_adjtime) timeval. Not included here are new versions
of getitimer/setitimer and getrusage/waitid, which are planned for the
future but only needed to make a consistent API rather than for correct
operation beyond y2038. These four system calls are based on 'timeval', and
it has not been finally decided what the replacement kernel interface will
use instead.

So far, I have done a lot of build testing across most architectures, which
has found a number of bugs. Runtime testing so far included testing LTP on
32-bit ARM with the existing system calls, to ensure we do not regress for
existing binaries, and a test with a 32-bit x86 build of LTP against a
modified version of the musl C library that has been adapted to the new
system call interface [3].  This library can be used for testing on all
architectures supported by musl-1.1.21, but it is not how the support is
getting integrated into the official musl release. Official musl support is
planned but will require more invasive changes to the library.

Link: https://lore.kernel.org/lkml/20190110162435.309262-1-arnd@arndb.de/T/
Link: https://lore.kernel.org/lkml/20190118161835.2259170-1-arnd@arndb.de/
Link: https://git.linaro.org/people/arnd/musl-y2038.git/ [2]
 2019-02-10 21:24:43 +01:00
Arnd Bergmann 8dabe7245b y2038: syscalls: rename y2038 compat syscalls 
A lot of system calls that pass a time_t somewhere have an implementation
using a COMPAT_SYSCALL_DEFINEx() on 64-bit architectures, and have
been reworked so that this implementation can now be used on 32-bit
architectures as well.

The missing step is to redefine them using the regular SYSCALL_DEFINEx()
to get them out of the compat namespace and make it possible to build them
on 32-bit architectures.

Any system call that ends in 'time' gets a '32' suffix on its name for
that version, while the others get a '_time32' suffix, to distinguish
them from the normal version, which takes a 64-bit time argument in the
future.

In this step, only 64-bit architectures are changed, doing this rename
first lets us avoid touching the 32-bit architectures twice.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
 2019-02-07 00:13:27 +01:00
Vincent Guittot f678331973 sched/fair: Fix insertion in rq->leaf_cfs_rq_list 
Sargun reported a crash:

  "I picked up c40f7d74c7 sched/fair: Fix
   infinite loop in update_blocked_averages() by reverting a9e7f6544b
   and put it on top of 4.19.13. In addition to this, I uninlined
   list_add_leaf_cfs_rq for debugging.

   This revealed a new bug that we didn't get to because we kept getting
   crashes from the previous issue. When we are running with cgroups that
   are rapidly changing, with CFS bandwidth control, and in addition
   using the cpusets cgroup, we see this crash. Specifically, it seems to
   occur with cgroups that are throttled and we change the allowed
   cpuset."

The algorithm used to order cfs_rq in rq->leaf_cfs_rq_list assumes that
it will walk down to root the 1st time a cfs_rq is used and we will finish
to add either a cfs_rq without parent or a cfs_rq with a parent that is
already on the list. But this is not always true in presence of throttling.
Because a cfs_rq can be throttled even if it has never been used but other CPUs
of the cgroup have already used all the bandwdith, we are not sure to go down to
the root and add all cfs_rq in the list.

Ensure that all cfs_rq will be added in the list even if they are throttled.

[ mingo: Fix !CGROUPS build. ]

Reported-by: Sargun Dhillon <sargun@sargun.me>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: tj@kernel.org
Fixes: 9c2791f936 ("Fix hierarchical order in rq->leaf_cfs_rq_list")
Link: https://lkml.kernel.org/r/1548825767-10799-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:14:48 +01:00
Peter Zijlstra 5d299eabea sched/fair: Add tmp_alone_branch assertion 
The magic in list_add_leaf_cfs_rq() requires that at the end of
enqueue_task_fair():

  rq->tmp_alone_branch == &rq->lead_cfs_rq_list

If this is violated, list integrity is compromised for list entries
and the tmp_alone_branch pointer might dangle.

Also, reflow list_add_leaf_cfs_rq() while there. This looses one
indentation level and generates a form that's convenient for the next
patch.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:13:21 +01:00
Andrea Parri c546951d9c sched/core: Use READ_ONCE()/WRITE_ONCE() in move_queued_task()/task_rq_lock() 
move_queued_task() synchronizes with task_rq_lock() as follows:

	move_queued_task()		task_rq_lock()

	[S] ->on_rq = MIGRATING		[L] rq = task_rq()
	WMB (__set_task_cpu())		ACQUIRE (rq->lock);
	[S] ->cpu = new_cpu		[L] ->on_rq

where "[L] rq = task_rq()" is ordered before "ACQUIRE (rq->lock)" by an
address dependency and, in turn, "ACQUIRE (rq->lock)" is ordered before
"[L] ->on_rq" by the ACQUIRE itself.

Use READ_ONCE() to load ->cpu in task_rq() (c.f., task_cpu()) to honor
this address dependency.  Also, mark the accesses to ->cpu and ->on_rq
with READ_ONCE()/WRITE_ONCE() to comply with the LKMM.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190121155240.27173-1-andrea.parri@amarulasolutions.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:13:21 +01:00
Hidetoshi Seto 1ca4fa3ab6 sched/debug: Initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK 
register_sched_domain_sysctl() copies the cpu_possible_mask into
sd_sysctl_cpus, but only if sd_sysctl_cpus hasn't already been
allocated (ie, CONFIG_CPUMASK_OFFSTACK is set).  However, when
CONFIG_CPUMASK_OFFSTACK is not set, sd_sysctl_cpus is left
uninitialized (all zeroes) and the kernel may fail to initialize
sched_domain sysctl entries for all possible CPUs.

This is visible to the user if the kernel is booted with maxcpus=n, or
if ACPI tables have been modified to leave CPUs offline, and then
checking for missing /proc/sys/kernel/sched_domain/cpu* entries.

Fix this by separating the allocation and initialization, and adding a
flag to initialize the possible CPU entries while system booting only.

Tested-by: Syuuichirou Ishii <ishii.shuuichir@jp.fujitsu.com>
Tested-by: Tarumizu, Kohei <tarumizu.kohei@jp.fujitsu.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190129151245.5073-1-msys.mizuma@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:13:21 +01:00
Vincent Guittot 10a35e6812 sched/pelt: Skip updating util_est when utilization is higher than CPU's capacity 
util_est is mainly meant to be a lower-bound for tasks utilization.
That's why task_util_est() returns the actual util_avg when it's higher
than the estimated utilization.

With new invaraince signal and without any special check on samples
collection, if a task is limited because of thermal capping for
example, we could end up overestimating its utilization and thus
perhaps generating an unwanted frequency spike when the capping is
relaxed... and (even worst) it will take some more activations for the
estimated utilization to converge back to the actual utilization.

Since we cannot easily know if there is idle time in a CPU when a task
completes an activation with a utilization higher then the CPU capacity,
we skip the sampling when utilization is higher than CPU's capacity.

Suggested-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: pjt@google.com
Cc: pkondeti@codeaurora.org
Cc: quentin.perret@arm.com
Cc: rjw@rjwysocki.net
Cc: srinivas.pandruvada@linux.intel.com
Cc: thara.gopinath@linaro.org
Link: https://lkml.kernel.org/r/1548257214-13745-4-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:13:21 +01:00
Vincent Guittot 2312729688 sched/fair: Update scale invariance of PELT 
The current implementation of load tracking invariance scales the
contribution with current frequency and uarch performance (only for
utilization) of the CPU. One main result of this formula is that the
figures are capped by current capacity of CPU. Another one is that the
load_avg is not invariant because not scaled with uarch.

The util_avg of a periodic task that runs r time slots every p time slots
varies in the range :

    U * (1-y^r)/(1-y^p) * y^i < Utilization < U * (1-y^r)/(1-y^p)

with U is the max util_avg value = SCHED_CAPACITY_SCALE

At a lower capacity, the range becomes:

    U * C * (1-y^r')/(1-y^p) * y^i' < Utilization <  U * C * (1-y^r')/(1-y^p)

with C reflecting the compute capacity ratio between current capacity and
max capacity.

so C tries to compensate changes in (1-y^r') but it can't be accurate.

Instead of scaling the contribution value of PELT algo, we should scale the
running time. The PELT signal aims to track the amount of computation of
tasks and/or rq so it seems more correct to scale the running time to
reflect the effective amount of computation done since the last update.

In order to be fully invariant, we need to apply the same amount of
running time and idle time whatever the current capacity. Because running
at lower capacity implies that the task will run longer, we have to ensure
that the same amount of idle time will be applied when system becomes idle
and no idle time has been "stolen". But reaching the maximum utilization
value (SCHED_CAPACITY_SCALE) means that the task is seen as an
always-running task whatever the capacity of the CPU (even at max compute
capacity). In this case, we can discard this "stolen" idle times which
becomes meaningless.

In order to achieve this time scaling, a new clock_pelt is created per rq.
The increase of this clock scales with current capacity when something
is running on rq and synchronizes with clock_task when rq is idle. With
this mechanism, we ensure the same running and idle time whatever the
current capacity. This also enables to simplify the pelt algorithm by
removing all references of uarch and frequency and applying the same
contribution to utilization and loads. Furthermore, the scaling is done
only once per update of clock (update_rq_clock_task()) instead of during
each update of sched_entities and cfs/rt/dl_rq of the rq like the current
implementation. This is interesting when cgroup are involved as shown in
the results below:

On a hikey (octo Arm64 platform).
Performance cpufreq governor and only shallowest c-state to remove variance
generated by those power features so we only track the impact of pelt algo.

each test runs 16 times:

	./perf bench sched pipe
	(higher is better)
	kernel	tip/sched/core     + patch
	        ops/seconds        ops/seconds         diff
	cgroup
	root    59652(+/- 0.18%)   59876(+/- 0.24%)    +0.38%
	level1  55608(+/- 0.27%)   55923(+/- 0.24%)    +0.57%
	level2  52115(+/- 0.29%)   52564(+/- 0.22%)    +0.86%

	hackbench -l 1000
	(lower is better)
	kernel	tip/sched/core     + patch
	        duration(sec)      duration(sec)        diff
	cgroup
	root    4.453(+/- 2.37%)   4.383(+/- 2.88%)     -1.57%
	level1  4.859(+/- 8.50%)   4.830(+/- 7.07%)     -0.60%
	level2  5.063(+/- 9.83%)   4.928(+/- 9.66%)     -2.66%

Then, the responsiveness of PELT is improved when CPU is not running at max
capacity with this new algorithm. I have put below some examples of
duration to reach some typical load values according to the capacity of the
CPU with current implementation and with this patch. These values has been
computed based on the geometric series and the half period value:

  Util (%)     max capacity  half capacity(mainline)  half capacity(w/ patch)
  972 (95%)    138ms         not reachable            276ms
  486 (47.5%)  30ms          138ms                     60ms
  256 (25%)    13ms           32ms                     26ms

On my hikey (octo Arm64 platform) with schedutil governor, the time to
reach max OPP when starting from a null utilization, decreases from 223ms
with current scale invariance down to 121ms with the new algorithm.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: patrick.bellasi@arm.com
Cc: pjt@google.com
Cc: pkondeti@codeaurora.org
Cc: quentin.perret@arm.com
Cc: rjw@rjwysocki.net
Cc: srinivas.pandruvada@linux.intel.com
Cc: thara.gopinath@linaro.org
Link: https://lkml.kernel.org/r/1548257214-13745-3-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:13:21 +01:00
Vincent Guittot 62478d9911 sched/fair: Move the rq_of() helper function 
Move rq_of() helper function so it can be used in pelt.c

[ mingo: Improve readability while at it. ]

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bsegall@google.com
Cc: dietmar.eggemann@arm.com
Cc: patrick.bellasi@arm.com
Cc: pjt@google.com
Cc: pkondeti@codeaurora.org
Cc: quentin.perret@arm.com
Cc: rjw@rjwysocki.net
Cc: srinivas.pandruvada@linux.intel.com
Cc: thara.gopinath@linaro.org
Link: https://lkml.kernel.org/r/1548257214-13745-2-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:13:21 +01:00
Davidlohr Bueso 07879c6a37 sched/wake_q: Reduce reference counting for special users 
Some users, specifically futexes and rwsems, required fixes
that allowed the callers to be safe when wakeups occur before
they are expected by wake_up_q(). Such scenarios also play
games and rely on reference counting, and until now were
pivoting on wake_q doing it. With the wake_q_add() call being
moved down, this can no longer be the case. As such we end up
with a a double task refcounting overhead; and these callers
care enough about this (being rather core-ish).

This patch introduces a wake_q_add_safe() call that serves
for callers that have already done refcounting and therefore the
task is 'safe' from wake_q point of view (int that it requires
reference throughout the entire queue/>wakeup cycle). In the one
case it has internal reference counting, in the other case it
consumes the reference counting.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Xie Yongji <xieyongji@baidu.com>
Cc: Yongji Xie <elohimes@gmail.com>
Cc: andrea.parri@amarulasolutions.com
Cc: lilin24@baidu.com
Cc: liuqi16@baidu.com
Cc: nixun@baidu.com
Cc: yuanlinsi01@baidu.com
Cc: zhangyu31@baidu.com
Link: https://lkml.kernel.org/r/20181218195352.7orq3upiwfdbrdne@linux-r8p5
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 09:03:28 +01:00
Ingo Molnar 31fe3cbbf2 Linux 5.0-rc5 
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Merge tag 'v5.0-rc5' into locking/core to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 08:57:24 +01:00
Elena Reshetova c45a779524 sched/fair: Convert numa_group.refcount to refcount_t 
atomic_t variables are currently used to implement reference
counters with the following properties:

 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable numa_group.refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

** Important note for maintainers:

Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.

The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.

Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.

Please double check that you don't have some undocumented
memory guarantees for this variable usage.

For the numa_group.refcount it might make a difference
in following places:

 - get_numa_group(): increment in refcount_inc_not_zero() only
   guarantees control dependency on success vs. fully ordered
   atomic counterpart
 - put_numa_group(): decrement in refcount_dec_and_test() only
   provides RELEASE ordering and control dependency on success
   vs. fully ordered atomic counterpart

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: viro@zeniv.linux.org.uk
Link: https://lkml.kernel.org/r/1547814450-18902-4-git-send-email-elena.reshetova@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-02-04 08:53:54 +01:00
Linus Torvalds cc6810e36b Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 
Pull cpu hotplug fixes from Thomas Gleixner:
 "Two fixes for the cpu hotplug machinery:

   - Replace the overly clever 'SMT disabled by BIOS' detection logic as
     it breaks KVM scenarios and prevents speculation control updates
     when the Hyperthreads are brought online late after boot.

   - Remove a redundant invocation of the speculation control update
     function"

* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM
  x86/speculation: Remove redundant arch_smt_update() invocation
 2019-02-03 09:02:03 -08:00
Johannes Weiner 1b69ac6b40 psi: fix aggregation idle shut-off 
psi has provisions to shut off the periodic aggregation worker when
there is a period of no task activity - and thus no data that needs
aggregating.  However, while developing psi monitoring, Suren noticed
that the aggregation clock currently won't stay shut off for good.

Debugging this revealed a flaw in the idle design: an aggregation run
will see no task activity and decide to go to sleep; shortly thereafter,
the kworker thread that executed the aggregation will go idle and cause
a scheduling change, during which the psi callback will kick the
!pending worker again.  This will ping-pong forever, and is equivalent
to having no shut-off logic at all (but with more code!)

Fix this by exempting aggregation workers from psi's clock waking logic
when the state change is them going to sleep.  To do this, tag workers
with the last work function they executed, and if in psi we see a worker
going to sleep after aggregating psi data, we will not reschedule the
aggregation work item.

What if the worker is also executing other items before or after?

Any psi state times that were incurred by work items preceding the
aggregation work will have been collected from the per-cpu buckets
during the aggregation itself.  If there are work items following the
aggregation work, the worker's last_func tag will be overwritten and the
aggregator will be kept alive to process this genuine new activity.

If the aggregation work is the last thing the worker does, and we decide
to go idle, the brief period of non-idle time incurred between the
aggregation run and the kworker's dequeue will be stranded in the
per-cpu buckets until the clock is woken by later activity.  But that
should not be a problem.  The buckets can hold 4s worth of time, and
future activity will wake the clock with a 2s delay, giving us 2s worth
of data we can leave behind when disabling aggregation.  If it takes a
worker more than two seconds to go idle after it finishes its last work
item, we likely have bigger problems in the system, and won't notice one
sample that was averaged with a bogus per-CPU weight.

Link: http://lkml.kernel.org/r/20190116193501.1910-1-hannes@cmpxchg.org
Fixes: eb414681d5 ("psi: pressure stall information for CPU, memory, and IO")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2019-02-01 15:46:23 -08:00
Josh Poimboeuf b284909aba cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM 
With the following commit:

  73d5e2b472 ("cpu/hotplug: detect SMT disabled by BIOS")

... the hotplug code attempted to detect when SMT was disabled by BIOS,
in which case it reported SMT as permanently disabled.  However, that
code broke a virt hotplug scenario, where the guest is booted with only
primary CPU threads, and a sibling is brought online later.

The problem is that there doesn't seem to be a way to reliably
distinguish between the HW "SMT disabled by BIOS" case and the virt
"sibling not yet brought online" case.  So the above-mentioned commit
was a bit misguided, as it permanently disabled SMT for both cases,
preventing future virt sibling hotplugs.

Going back and reviewing the original problems which were attempted to
be solved by that commit, when SMT was disabled in BIOS:

  1) /sys/devices/system/cpu/smt/control showed "on" instead of
     "notsupported"; and

  2) vmx_vm_init() was incorrectly showing the L1TF_MSG_SMT warning.

I'd propose that we instead consider #1 above to not actually be a
problem.  Because, at least in the virt case, it's possible that SMT
wasn't disabled by BIOS and a sibling thread could be brought online
later.  So it makes sense to just always default the smt control to "on"
to allow for that possibility (assuming cpuid indicates that the CPU
supports SMT).

The real problem is #2, which has a simple fix: change vmx_vm_init() to
query the actual current SMT state -- i.e., whether any siblings are
currently online -- instead of looking at the SMT "control" sysfs value.

So fix it by:

  a) reverting the original "fix" and its followup fix:

     73d5e2b472 ("cpu/hotplug: detect SMT disabled by BIOS")
     bc2d8d262c ("cpu/hotplug: Fix SMT supported evaluation")

     and

  b) changing vmx_vm_init() to query the actual current SMT state --
     instead of the sysfs control value -- to determine whether the L1TF
     warning is needed.  This also requires the 'sched_smt_present'
     variable to exported, instead of 'cpu_smt_control'.

Fixes: 73d5e2b472 ("cpu/hotplug: detect SMT disabled by BIOS")
Reported-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Joe Mario <jmario@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/e3a85d585da28cc333ecbc1e78ee9216e6da9396.1548794349.git.jpoimboe@redhat.com
 2019-01-30 19:27:00 +01:00
Vincent Guittot 46a745d905 sched/fair: Fix unnecessary increase of balance interval 
In case of active balancing, we increase the balance interval to cover
pinned tasks cases not covered by all_pinned logic. Neverthless, the
active migration triggered by asym packing should be treated as the normal
unbalanced case and reset the interval to default value, otherwise active
migration for asym_packing can be easily delayed for hundreds of ms
because of this pinned task detection mechanism.

The same happens to other conditions tested in need_active_balance() like
misfit task and when the capacity of src_cpu is reduced compared to
dst_cpu (see comments in need_active_balance() for details).

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: valentin.schneider@arm.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-01-27 12:29:37 +01:00
Vincent Guittot 4ad4e481bd sched/fair: Fix rounding bug for asym packing 
When check_asym_packing() is triggered, the imbalance is set to:

  busiest_stat.avg_load * busiest_stat.group_capacity / SCHED_CAPACITY_SCALE

But busiest_stat.avg_load equals:

  sgs->group_load * SCHED_CAPACITY_SCALE / sgs->group_capacity

These divisions can generate a rounding that will make imbalance
slightly lower than the weighted load of the cfs_rq.  But this is
enough to skip the rq in find_busiest_queue() and prevents asym
migration from happening.

Directly set imbalance to busiest's sgs->group_load to remove the
rounding.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: valentin.schneider@arm.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-01-27 12:29:37 +01:00
Vincent Guittot a062d16449 sched/fair: Trigger asym_packing during idle load balance 
Newly idle load balancing is not always triggered when a CPU becomes idle.
This prevents the scheduler from getting a chance to migrate the task
for asym packing.

Enable active migration during idle load balance too.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: valentin.schneider@arm.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-01-27 12:29:37 +01:00
Peter Zijlstra c0ad4aa4d8 sched/fair: Robustify CFS-bandwidth timer locking 
Traditionally hrtimer callbacks were run with IRQs disabled, but with
the introduction of HRTIMER_MODE_SOFT it is possible they run from
SoftIRQ context, which does _NOT_ have IRQs disabled.

Allow for the CFS bandwidth timers (period_timer and slack_timer) to
be ran from SoftIRQ context; this entails removing the assumption that
IRQs are already disabled from the locking.

While mainline doesn't strictly need this, -RT forces all timers not
explicitly marked with MODE_HARD into MODE_SOFT and trips over this.
And marking these timers as MODE_HARD doesn't make sense as they're
not required for RT operation and can potentially be quite expensive.

Reported-by: Tom Putzeys <tom.putzeys@be.atlascopco.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190107125231.GE14122@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-01-27 12:29:37 +01:00
Peter Zijlstra f8a696f25b sched/core: Give DCE a fighting chance 
All that fancy new Energy-Aware scheduling foo is hidden behind a
static_key, which is awesome if you have the stuff enabled in your
config.

However, when you lack all the prerequisites it doesn't make any sense
to pretend we'll ever actually run this, so provide a little more clue
to the compiler so it can more agressively delete the code.

   text    data     bss     dec     hex filename
  50297     976      96   51369    c8a9 defconfig-build/kernel/sched/fair.o
  49227     944      96   50267    c45b defconfig-build/kernel/sched/fair.o

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-01-27 12:29:37 +01:00
Quentin Perret 8d5d0cfb63 sched/topology: Introduce a sysctl for Energy Aware Scheduling 
In its current state, Energy Aware Scheduling (EAS) starts automatically
on asymmetric platforms having an Energy Model (EM). However, there are
users who want to have an EM (for thermal management for example), but
don't want EAS with it.

In order to let users disable EAS explicitly, introduce a new sysctl
called 'sched_energy_aware'. It is enabled by default so that EAS can
start automatically on platforms where it makes sense. Flipping it to 0
rebuilds the scheduling domains and disables EAS.

Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: adharmap@codeaurora.org
Cc: chris.redpath@arm.com
Cc: currojerez@riseup.net
Cc: dietmar.eggemann@arm.com
Cc: edubezval@gmail.com
Cc: gregkh@linuxfoundation.org
Cc: javi.merino@kernel.org
Cc: joel@joelfernandes.org
Cc: juri.lelli@redhat.com
Cc: morten.rasmussen@arm.com
Cc: patrick.bellasi@arm.com
Cc: pkondeti@codeaurora.org
Cc: rjw@rjwysocki.net
Cc: skannan@codeaurora.org
Cc: smuckle@google.com
Cc: srinivas.pandruvada@linux.intel.com
Cc: thara.gopinath@linaro.org
Cc: tkjos@google.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Cc: viresh.kumar@linaro.org
Link: https://lkml.kernel.org/r/20181203095628.11858-11-quentin.perret@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2019-01-27 12:29:37 +01:00