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  1. 11 12月, 2016 1 次提交
    • V
      sched/core: Fix find_idlest_group() for fork · f519a3f1
      由 Vincent Guittot 提交于 
      During fork, the utilization of a task is init once the rq has been
selected because the current utilization level of the rq is used to
set the utilization of the fork task. As the task's utilization is
still 0 at this step of the fork sequence, it doesn't make sense to
look for some spare capacity that can fit the task's utilization.
Furthermore, I can see perf regressions for the test:

   hackbench -P -g 1

because the least loaded policy is always bypassed and tasks are not
spread during fork.

With this patch and the fix below, we are back to same performances as
for v4.8. The fix below is only a temporary one used for the test
until a smarter solution is found because we can't simply remove the
test which is useful for others benchmarks

| @@ -5708,13 +5708,6 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
|
|	avg_cost = this_sd->avg_scan_cost;
|
| -	/*
| -	 * Due to large variance we need a large fuzz factor; hackbench in
| -	 * particularly is sensitive here.
| -	 */
| -	if ((avg_idle / 512) < avg_cost)
| -		return -1;
| -
|	time = local_clock();
|
|	for_each_cpu_wrap(cpu, sched_domain_span(sd), target, wrap) {
Tested-by: NMatt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NMatt Fleming <matt@codeblueprint.co.uk>
Acked-by: NMorten Rasmussen <morten.rasmussen@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: kernellwp@gmail.com
Cc: umgwanakikbuti@gmail.com
Cc: yuyang.du@intel.comc
Link: http://lkml.kernel.org/r/1481216215-24651-2-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      f519a3f1
  3. 24 11月, 2016 2 次提交
  5. 23 11月, 2016 2 次提交
  7. 22 11月, 2016 2 次提交
    • O
      sched/autogroup: Do not use autogroup->tg in zombie threads · 8e5bfa8c
      由 Oleg Nesterov 提交于 
      Exactly because for_each_thread() in autogroup_move_group() can't see it
and update its ->sched_task_group before _put() and possibly free().

So the exiting task needs another sched_move_task() before exit_notify()
and we need to re-introduce the PF_EXITING (or similar) check removed by
the previous change for another reason.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NPeter 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: hartsjc@redhat.com
Cc: vbendel@redhat.com
Cc: vlovejoy@redhat.com
Link: http://lkml.kernel.org/r/20161114184612.GA15968@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      8e5bfa8c
    • O
      sched/autogroup: Fix autogroup_move_group() to never skip sched_move_task() · 18f649ef
      由 Oleg Nesterov 提交于 
      The PF_EXITING check in task_wants_autogroup() is no longer needed. Remove
it, but see the next patch.

However the comment is correct in that autogroup_move_group() must always
change task_group() for every thread so the sysctl_ check is very wrong;
we can race with cgroups and even sys_setsid() is not safe because a task
running with task_group() == ag->tg must participate in refcounting:

	int main(void)
	{
		int sctl = open("/proc/sys/kernel/sched_autogroup_enabled", O_WRONLY);

		assert(sctl > 0);
		if (fork()) {
			wait(NULL); // destroy the child's ag/tg
			pause();
		}

		assert(pwrite(sctl, "1\n", 2, 0) == 2);
		assert(setsid() > 0);
		if (fork())
			pause();

		kill(getppid(), SIGKILL);
		sleep(1);

		// The child has gone, the grandchild runs with kref == 1
		assert(pwrite(sctl, "0\n", 2, 0) == 2);
		assert(setsid() > 0);

		// runs with the freed ag/tg
		for (;;)
			sleep(1);

		return 0;
	}

crashes the kernel. It doesn't really need sleep(1), it doesn't matter if
autogroup_move_group() actually frees the task_group or this happens later.
Reported-by: NVern Lovejoy <vlovejoy@redhat.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NPeter 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: hartsjc@redhat.com
Cc: vbendel@redhat.com
Link: http://lkml.kernel.org/r/20161114184609.GA15965@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      18f649ef
  9. 16 11月, 2016 12 次提交
  11. 15 11月, 2016 3 次提交
  13. 11 11月, 2016 1 次提交
  15. 03 11月, 2016 2 次提交
  17. 28 10月, 2016 1 次提交
    • L
      mm: remove per-zone hashtable of bitlock waitqueues · 9dcb8b68
      由 Linus Torvalds 提交于 
      The per-zone waitqueues exist because of a scalability issue with the
page waitqueues on some NUMA machines, but it turns out that they hurt
normal loads, and now with the vmalloced stacks they also end up
breaking gfs2 that uses a bit_wait on a stack object:

     wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE)

where 'gh' can be a reference to the local variable 'mount_gh' on the
stack of fill_super().

The reason the per-zone hash table breaks for this case is that there is
no "zone" for virtual allocations, and trying to look up the physical
page to get at it will fail (with a BUG_ON()).

It turns out that I actually complained to the mm people about the
per-zone hash table for another reason just a month ago: the zone lookup
also hurts the regular use of "unlock_page()" a lot, because the zone
lookup ends up forcing several unnecessary cache misses and generates
horrible code.

As part of that earlier discussion, we had a much better solution for
the NUMA scalability issue - by just making the page lock have a
separate contention bit, the waitqueue doesn't even have to be looked at
for the normal case.

Peter Zijlstra already has a patch for that, but let's see if anybody
even notices.  In the meantime, let's fix the actual gfs2 breakage by
simplifying the bitlock waitqueues and removing the per-zone issue.
Reported-by: NAndreas Gruenbacher <agruenba@redhat.com>
Tested-by: NBob Peterson <rpeterso@redhat.com>
Acked-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9dcb8b68
  19. 27 10月, 2016 1 次提交
  21. 25 10月, 2016 1 次提交
  23. 20 10月, 2016 1 次提交
  25. 19 10月, 2016 1 次提交
    • V
      sched/fair: Fix incorrect task group ->load_avg · b5a9b340
      由 Vincent Guittot 提交于 
      A scheduler performance regression has been reported by Joseph Salisbury,
which he bisected back to:

  3d30544f ("sched/fair: Apply more PELT fixes)

The regression triggers when several levels of task groups are involved
(read: SystemD) and cpu_possible_mask != cpu_present_mask.

The root cause is that group entity's load (tg_child->se[i]->avg.load_avg)
is initialized to scale_load_down(se->load.weight). During the creation of
a child task group, its group entities on possible CPUs are attached to
parent's cfs_rq (tg_parent) and their loads are added to the parent's load
(tg_parent->load_avg) with update_tg_load_avg().

But only the load on online CPUs will then be updated to reflect real load,
whereas load on other CPUs will stay at the initial value.

The result is a tg_parent->load_avg that is higher than the real load, the
weight of group entities (tg_parent->se[i]->load.weight) on online CPUs is
smaller than it should be, and the task group gets a less running time than
what it could expect.

( This situation can be detected with /proc/sched_debug. The ".tg_load_avg"
  of the task group will be much higher than sum of ".tg_load_avg_contrib"
  of online cfs_rqs of the task group. )

The load of group entities don't have to be intialized to something else
than 0 because their load will increase when an entity is attached.
Reported-by: NJoseph Salisbury <joseph.salisbury@canonical.com>
Tested-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@vger.kernel.org> # 4.8.x
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: joonwoop@codeaurora.org
Fixes: 3d30544f ("sched/fair: Apply more PELT fixes)
Link: http://lkml.kernel.org/r/1476881123-10159-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      b5a9b340
  27. 11 10月, 2016 2 次提交
    • W
      sched/fair: Fix sched domains NULL dereference in select_idle_sibling() · 9cfb38a7
      由 Wanpeng Li 提交于 
      Commit:

  10e2f1ac ("sched/core: Rewrite and improve select_idle_siblings()")

... improved select_idle_sibling(), but also triggered a regression (crash)
during CPU-hotplug:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000078
  IP: [<ffffffffb10cd332>] select_idle_sibling+0x1c2/0x4f0
  Call Trace:
   <IRQ>
    select_task_rq_fair+0x749/0x930
    ? select_task_rq_fair+0xb4/0x930
    ? __lock_is_held+0x54/0x70
    try_to_wake_up+0x19a/0x5b0
    default_wake_function+0x12/0x20
    autoremove_wake_function+0x12/0x40
    __wake_up_common+0x55/0x90
    __wake_up+0x39/0x50
    wake_up_klogd_work_func+0x40/0x60
    irq_work_run_list+0x57/0x80
    irq_work_run+0x2c/0x30
    smp_irq_work_interrupt+0x2e/0x40
    irq_work_interrupt+0x96/0xa0
   <EOI>
    ? _raw_spin_unlock_irqrestore+0x45/0x80
    try_to_wake_up+0x4a/0x5b0
    wake_up_state+0x10/0x20
    __kthread_unpark+0x67/0x70
    kthread_unpark+0x22/0x30
    cpuhp_online_idle+0x3e/0x70
    cpu_startup_entry+0x6a/0x450
    start_secondary+0x154/0x180

This can be reproduced by running the ftrace test case of kselftest, the
test case will hot-unplug the CPU and the CPU will attach to the NULL
sched-domain during scheduler teardown.

The step 2 for the rewrite select_idle_siblings():

  | Step 2) tracks the average cost of the scan and compares this to the
  | average idle time guestimate for the CPU doing the wakeup.

If the CPU which doing the wakeup is the going hot-unplug CPU, then NULL
sched domain will be dereferenced to acquire the average cost of the scan.

This patch fix it by failing the search of an idle CPU in the LLC process
if this sched domain is NULL.
Tested-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.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>
Link: http://lkml.kernel.org/r/1475971443-3187-1-git-send-email-wanpeng.li@hotmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      9cfb38a7
    • E
      latent_entropy: Mark functions with __latent_entropy · 0766f788
      由 Emese Revfy 提交于 
      The __latent_entropy gcc attribute can be used only on functions and
variables.  If it is on a function then the plugin will instrument it for
gathering control-flow entropy. If the attribute is on a variable then
the plugin will initialize it with random contents.  The variable must
be an integer, an integer array type or a structure with integer fields.

These specific functions have been selected because they are init
functions (to help gather boot-time entropy), are called at unpredictable
times, or they have variable loops, each of which provide some level of
latent entropy.
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
[kees: expanded commit message]
Signed-off-by: NKees Cook <keescook@chromium.org>
      0766f788
  29. 08 10月, 2016 1 次提交
  31. 30 9月, 2016 7 次提交