linux-stable.git/kernel/sched, branch v4.0.3

sched/deadline: Always enqueue on previous rq when dl_task_timer() fires

2015-05-06T20:04:06+00:00

commit 4cd57f97135840f637431c92380c8da3edbe44ed upstream.

dl_task_timer() may fire on a different rq from where a task was removed
after throttling. Since the call path is:

  dl_task_timer() ->
    enqueue_task_dl() ->
      enqueue_dl_entity() ->
        replenish_dl_entity()

and replenish_dl_entity() uses dl_se's rq, we can't use current's rq
in dl_task_timer(), but we need to lock the task's previous one.

Tested-by: Wanpeng Li 
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Kirill Tkhai 
Cc: Juri Lelli 
Fixes: 3960c8c0c789 ("sched: Make dl_task_time() use task_rq_lock()")
Link: http://lkml.kernel.org/r/1427792017-7356-1-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

x86: kvm: Revert "remove sched notifier for cross-cpu migrations"

2015-05-06T20:03:36+00:00

commit 0a4e6be9ca17c54817cf814b4b5aa60478c6df27 upstream.

The following point:

    2. per-CPU pvclock time info is updated if the
       underlying CPU changes.

Is not true anymore since "KVM: x86: update pvclock area conditionally,
on cpu migration".

Add task migration notification back.

Problem noticed by Andy Lutomirski.

Signed-off-by: Marcelo Tosatti 
Signed-off-by: Greg Kroah-Hartman

mm: numa: disable change protection for vma(VM_HUGETLB)

2015-04-07T23:45:33+00:00

Currently when a process accesses a hugetlb range protected with
PROTNONE, unexpected COWs are triggered, which finally puts the hugetlb
subsystem into a broken/uncontrollable state, where for example
h->resv_huge_pages is subtracted too much and wraps around to a very
large number, and the free hugepage pool is no longer maintainable.

This patch simply stops changing protection for vma(VM_HUGETLB) to fix
the problem.  And this also allows us to avoid useless overhead of minor
faults.

Signed-off-by: Naoya Horiguchi 
Suggested-by: Mel Gorman 
Cc: Hugh Dickins 
Cc: "Kirill A. Shutemov" 
Cc: David Rientjes 
Cc: Rik van Riel 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-03-28T18:17:32+00:00

Pull scheduler fix from Ingo Molnar:
 "A single sched/rt corner case fix for RLIMIT_RTIME correctness"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix RLIMIT_RTTIME when PI-boosting to RT

mm: numa: slow PTE scan rate if migration failures occur

2015-03-25T23:20:31+00:00

Dave Chinner reported the following on https://lkml.org/lkml/2015/3/1/226

  Across the board the 4.0-rc1 numbers are much slower, and the degradation
  is far worse when using the large memory footprint configs. Perf points
  straight at the cause - this is from 4.0-rc1 on the "-o bhash=101073" config:

   -   56.07%    56.07%  [kernel]            [k] default_send_IPI_mask_sequence_phys
      - default_send_IPI_mask_sequence_phys
         - 99.99% physflat_send_IPI_mask
            - 99.37% native_send_call_func_ipi
                 smp_call_function_many
               - native_flush_tlb_others
                  - 99.85% flush_tlb_page
                       ptep_clear_flush
                       try_to_unmap_one
                       rmap_walk
                       try_to_unmap
                       migrate_pages
                       migrate_misplaced_page
                     - handle_mm_fault
                        - 99.73% __do_page_fault
                             trace_do_page_fault
                             do_async_page_fault
                           + async_page_fault
              0.63% native_send_call_func_single_ipi
                 generic_exec_single
                 smp_call_function_single

This is showing excessive migration activity even though excessive
migrations are meant to get throttled.  Normally, the scan rate is tuned
on a per-task basis depending on the locality of faults.  However, if
migrations fail for any reason then the PTE scanner may scan faster if
the faults continue to be remote.  This means there is higher system CPU
overhead and fault trapping at exactly the time we know that migrations
cannot happen.  This patch tracks when migration failures occur and
slows the PTE scanner.

Signed-off-by: Mel Gorman 
Reported-by: Dave Chinner 
Tested-by: Dave Chinner 
Cc: Ingo Molnar 
Cc: Aneesh Kumar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sched: Fix RLIMIT_RTTIME when PI-boosting to RT

2015-03-23T09:47:55+00:00

When non-realtime tasks get priority-inheritance boosted to a realtime
scheduling class, RLIMIT_RTTIME starts to apply to them. However, the
counter used for checking this (the same one used for SCHED_RR
timeslices) was not getting reset. This meant that tasks running with a
non-realtime scheduling class which are repeatedly boosted to a realtime
one, but never block while they are running realtime, eventually hit the
timeout without ever running for a time over the limit. This patch
resets the realtime timeslice counter when un-PI-boosting from an RT to
a non-RT scheduling class.

I have some test code with two threads and a shared PTHREAD_PRIO_INHERIT
mutex which induces priority boosting and spins while boosted that gets
killed by a SIGXCPU on non-fixed kernels but doesn't with this patch
applied. It happens much faster with a CONFIG_PREEMPT_RT kernel, and
does happen eventually with PREEMPT_VOLUNTARY kernels.

Signed-off-by: Brian Silverman 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: austin@peloton-tech.com
Cc: 
Link: http://lkml.kernel.org/r/1424305436-6716-1-git-send-email-brian@peloton-tech.com
Signed-off-by: Ingo Molnar

cpuidle / sleep: Use broadcast timer for states that stop local timer

2015-03-05T22:13:19+00:00

Commit 381063133246 (PM / sleep: Re-implement suspend-to-idle handling)
overlooked the fact that entering some sufficiently deep idle states
by CPUs may cause their local timers to stop and in those cases it
is necessary to switch over to a broadcast timer prior to entering
the idle state.  If the cpuidle driver in use does not provide
the new ->enter_freeze callback for any of the idle states, that
problem affects suspend-to-idle too, but it is not taken into account
after the changes made by commit 381063133246.

Fix that by changing the definition of cpuidle_enter_freeze() and
re-arranging of the code in cpuidle_idle_call(), so the former does
not call cpuidle_enter() any more and the fallback case is handled
by cpuidle_idle_call() directly.

Fixes: 381063133246 (PM / sleep: Re-implement suspend-to-idle handling)
Reported-and-tested-by: Lorenzo Pieralisi 
Signed-off-by: Rafael J. Wysocki 
Acked-by: Peter Zijlstra (Intel)

cpuidle: Clean up fallback handling in cpuidle_idle_call()

2015-03-02T21:25:37+00:00

Move the fallback code path in cpuidle_idle_call() to the end of the
function to avoid jumping to a label in an if () branch.

Signed-off-by: Rafael J. Wysocki

idle / sleep: Avoid excessive disabling and enabling interrupts

2015-02-28T22:46:24+00:00

Disabling interrupts at the end of cpuidle_enter_freeze() is not
useful, because its caller, cpuidle_idle_call(), re-enables them
right away after invoking it.

To avoid that unnecessary back and forth dance with interrupts,
make cpuidle_enter_freeze() enable interrupts after calling
enter_freeze_proper() and drop the local_irq_disable() at its
end, so that all of the code paths in it end up with interrupts
enabled.  Then, cpuidle_idle_call() will not need to re-enable
interrupts after calling cpuidle_enter_freeze() any more, because
the latter will return with interrupts enabled, in analogy with
cpuidle_enter().

Reported-by: Lorenzo Pieralisi 
Signed-off-by: Rafael J. Wysocki 
Acked-by: Peter Zijlstra (Intel)

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-02-21T18:40:02+00:00

Pull scheduler fixes from Ingo Molnar:
 "Thiscontains misc fixes: preempt_schedule_common() and io_schedule()
  recursion fixes, sched/dl fixes, a completion_done() revert, two
  sched/rt fixes and a comment update patch"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/rt: Avoid obvious configuration fail
  sched/autogroup: Fix failure to set cpu.rt_runtime_us
  sched/dl: Do update_rq_clock() in yield_task_dl()
  sched: Prevent recursion in io_schedule()
  sched/completion: Serialize completion_done() with complete()
  sched: Fix preempt_schedule_common() triggering tracing recursion
  sched/dl: Prevent enqueue of a sleeping task in dl_task_timer()
  sched: Make dl_task_time() use task_rq_lock()
  sched: Clarify ordering between task_rq_lock() and move_queued_task()