Commit Graph

1314 Commits

Author SHA1 Message Date
Frederic Weisbecker 55dbdcfa05 sched/cputime: Rename vtime_accounting_enabled() to vtime_accounting_cpu_enabled()
vtime_accounting_enabled() checks if vtime is running on the current CPU
and is as such a misnomer. Lets rename it to a function that reflect its
locality. We are going to need the current name for a function that tells
if vtime runs at all on some CPU.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447948054-28668-6-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:34:45 +01:00
Frederic Weisbecker cab245d68c sched/cputime: Correctly handle task guest time on housekeepers
When a task runs on a housekeeper (a CPU running with the periodic tick
with neighbours running tickless), it doesn't account cputime using vtime
but relies on the tick. Such a task has its vtime_snap_whence value set
to VTIME_INACTIVE.

Readers won't handle that correctly though. As long as vtime is running
on some CPU, readers incorretly assume that vtime runs on all CPUs and
always compute the tickless cputime delta, which is only junk on
housekeepers.

So lets fix this with checking that the target runs on a vtime CPU through
the appropriate state check before computing the tickless delta.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447948054-28668-5-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:34:44 +01:00
Frederic Weisbecker 7098c1eac7 sched/cputime: Clarify vtime symbols and document them
VTIME_SLEEPING state happens either when:

1) The task is sleeping and no tickless delta is to be added on the task
   cputime stats.
2) The CPU isn't running vtime at all, so the same properties of 1) applies.

Lets rename the vtime symbol to reflect both states.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447948054-28668-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:34:44 +01:00
Hiroshi Shimamoto 7877a0ba5e sched/cputime: Remove extra cost in task_cputime()
There is an extra cost in task_cputime() and task_cputime_scaled() when
nohz_full is not activated. When vtime accounting is not enabled, we
don't need to get deltas of utime and stime under vtime seqlock.

This patch removes that cost with adding a shortcut route if vtime
accounting is not enabled.

Use context_tracking_is_enabled() to check if vtime is accounting on
some cpu, in which case only we need to check the tickless cputime delta.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447948054-28668-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:34:43 +01:00
Byungchul Park ad936d8658 sched/fair: Make it possible to account fair load avg consistently
The current code accounts for the time a task was absent from the fair
class (per ATTACH_AGE_LOAD). However it does not work correctly when a
task got migrated or moved to another cgroup while outside of the fair
class.

This patch tries to address that by aging on migration. We locklessly
read the 'last_update_time' stamp from both the old and new cfs_rq,
ages the load upto the old time, and sets it to the new time.

These timestamps should in general not be more than 1 tick apart from
one another, so there is a definite bound on things.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
[ Changelog, a few edits and !SMP build fix ]
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>
Link: http://lkml.kernel.org/r/1445616981-29904-2-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:34:42 +01:00
Ingo Molnar 467386fbbf Merge branch 'sched/urgent' into sched/core, to pick up fixes before applying new changes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:27:36 +01:00
Peter Zijlstra ecf7d01c22 sched/core: Fix an SMP ordering race in try_to_wake_up() vs. schedule()
Oleg noticed that its possible to falsely observe p->on_cpu == 0 such
that we'll prematurely continue with the wakeup and effectively run p on
two CPUs at the same time.

Even though the overlap is very limited; the task is in the middle of
being scheduled out; it could still result in corruption of the
scheduler data structures.

        CPU0                            CPU1

        set_current_state(...)

        <preempt_schedule>
          context_switch(X, Y)
            prepare_lock_switch(Y)
              Y->on_cpu = 1;
            finish_lock_switch(X)
              store_release(X->on_cpu, 0);

                                        try_to_wake_up(X)
                                          LOCK(p->pi_lock);

                                          t = X->on_cpu; // 0

          context_switch(Y, X)
            prepare_lock_switch(X)
              X->on_cpu = 1;
            finish_lock_switch(Y)
              store_release(Y->on_cpu, 0);
        </preempt_schedule>

        schedule();
          deactivate_task(X);
          X->on_rq = 0;

                                          if (X->on_rq) // false

                                          if (t) while (X->on_cpu)
                                            cpu_relax();

          context_switch(X, ..)
            finish_lock_switch(X)
              store_release(X->on_cpu, 0);

Avoid the load of X->on_cpu being hoisted over the X->on_rq load.

Reported-by: Oleg Nesterov <oleg@redhat.com>
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>
2015-12-04 10:26:43 +01:00
Peter Zijlstra b75a225315 sched/core: Better document the try_to_wake_up() barriers
Explain how the control dependency and smp_rmb() end up providing
ACQUIRE semantics and pair with smp_store_release() in
finish_lock_switch().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:26:42 +01:00
Hiroshi Shimamoto 2541117b0c sched/cputime: Fix invalid gtime in proc
/proc/stats shows invalid gtime when the thread is running in guest.
When vtime accounting is not enabled, we cannot get a valid delta.
The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap
is only updated when vtime accounting is runtime enabled.

This patch makes task_gtime() just return gtime without computing the
buggy non-existing tickless delta when vtime accounting is not enabled.

Use context_tracking_is_enabled() to check if vtime is accounting on
some cpu, in which case only we need to check the tickless delta. This
way we fix the gtime value regression on machines not running nohz full.

The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and
CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full.

I ran and stop a busy loop in VM and see the gtime in host.
Dump the 43rd field which shows the gtime in every second:

	 # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done
	S 4348
	R 7064566
	R 7064766
	R 7064967
	R 7065168
	S 4759
	S 4759

During running busy loop, it returns large value.

After applying this patch, we can see right gtime.

	 # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done
	S 5338
	R 5365
	R 5465
	R 5566
	R 5666
	S 5726
	S 5726

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:18:49 +01:00
Xunlei Pang 8295c69925 sched/core: Clear the root_domain cpumasks in init_rootdomain()
root_domain::rto_mask allocated through alloc_cpumask_var()
contains garbage data, this may cause problems. For instance,
When doing pull_rt_task(), it may do useless iterations if
rto_mask retains some extra garbage bits. Worse still, this
violates the isolated domain rule for clustered scheduling
using cpuset, because the tasks(with all the cpus allowed)
belongs to one root domain can be pulled away into another
root domain.

The patch cleans the garbage by using zalloc_cpumask_var()
instead of alloc_cpumask_var() for root_domain::rto_mask
allocation, thereby addressing the issues.

Do the same thing for root_domain's other cpumask memembers:
dlo_mask, span, and online.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1449057179-29321-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:16:21 +01:00
Sasha Levin 119d6f6a3b sched/core: Remove false-positive warning from wake_up_process()
Because wakeups can (fundamentally) be late, a task might not be in
the expected state. Therefore testing against a task's state is racy,
and can yield false positives.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: 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: oleg@redhat.com
Fixes: 9067ac85d5 ("wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task")
Link: http://lkml.kernel.org/r/1448933660-23082-1-git-send-email-sasha.levin@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:10:16 +01:00
Peter Zijlstra 68985633bc sched/wait: Fix signal handling in bit wait helpers
Vladimir reported getting RCU stall warnings and bisected it back to
commit:

  743162013d ("sched: Remove proliferation of wait_on_bit() action functions")

That commit inadvertently reversed the calls to schedule() and signal_pending(),
thereby not handling the case where the signal receives while we sleep.

Reported-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
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: mark.rutland@arm.com
Cc: neilb@suse.de
Cc: oleg@redhat.com
Fixes: 743162013d ("sched: Remove proliferation of wait_on_bit() action functions")
Fixes: cbbce82209 ("SCHED: add some "wait..on_bit...timeout()" interfaces.")
Link: http://lkml.kernel.org/r/20151201130404.GL3816@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-12-04 10:10:15 +01:00
Byungchul Park 525628c73b sched/fair: Modify the comment about lock assumptions in migrate_task_rq_fair()
The comment describing migrate_task_rq_fair() says that the caller
should hold p->pi_lock. But in some cases the caller can hold
task_rq(p)->lock instead of p->pi_lock. So the comment is broken and
this patch fixes it.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
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>
Link: http://lkml.kernel.org/r/1447806899-20303-1-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:48:20 +01:00
Geliang Tang 01783e0d45 sched/core: Use list_is_singular() in sched_can_stop_tick()
Use list_is_singular() to check if run_list has only one entry.

Signed-off-by: Geliang Tang <geliangtang@163.com>
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>
Link: http://lkml.kernel.org/r/a5453fafd735affcf28e53a1d0a3d6965cb5dbb5.1447582547.git.geliangtang@163.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:48:17 +01:00
Joonwoo Park 3ea94de15c sched/core: Fix incorrect wait time and wait count statistics
At present scheduler resets task's wait start timestamp when the task
migrates to another rq.  This misleads scheduler itself into reporting
less wait time than actual by omitting time spent for waiting prior to
migration and also more wait count than actual by counting migration as
wait end event which can be seen by trace or /proc/<pid>/sched with
CONFIG_SCHEDSTATS=y.

Carry forward migrating task's wait time prior to migration and
don't count migration as a wait end event to fix such statistics error.

In order to determine whether task is migrating mark task->on_rq with
TASK_ON_RQ_MIGRATING while dequeuing and enqueuing due to migration.

Signed-off-by: Joonwoo Park <joonwoop@codeaurora.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: ohaugan@codeaurora.org
Link: http://lkml.kernel.org/r/20151113033854.GA4247@codeaurora.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:48:17 +01:00
Rik van Riel 51170840fe sched/numa: Cap PTE scanning overhead to 3% of run time
There is a fundamental mismatch between the runtime based NUMA scanning
at the task level, and the wall clock time NUMA scanning at the mm level.
On a severely overloaded system, with very large processes, this mismatch
can cause the system to spend all of its time in change_prot_numa().

This can happen if the task spends at least two ticks in change_prot_numa(),
and only gets two ticks of CPU time in the real time between two scan
intervals of the mm.

This patch ensures that a task never spends more than 3% of run
time scanning PTEs. It does that by ensuring that in-between
task_numa_work() runs, the task spends at least 32x as much time on
other things than it did on task_numa_work().

This is done stochastically: if a timer tick happens, or the task
gets rescheduled during task_numa_work(), we delay a future run of
task_numa_work() until the task has spent at least 32x the amount of
CPU time doing something else, as it spent inside task_numa_work().
The longer task_numa_work() takes, the more likely it is this happens.

If task_numa_work() takes very little time, chances are low that that
code will do anything, but we will not care.

Reported-and-tested-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
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: mgorman@suse.de
Link: http://lkml.kernel.org/r/1446756983-28173-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:37:54 +01:00
Byungchul Park 525705d15e sched/fair: Consider missed ticks in NOHZ_FULL in update_cpu_load_nohz()
Usually the tick can be stopped for an idle CPU in NOHZ. However in NOHZ_FULL
mode, a non-idle CPU's tick can also be stopped. However, update_cpu_load_nohz()
does not consider the case a non-idle CPU's tick has been stopped at all.

This patch makes the update_cpu_load_nohz() know if the calling path comes
from NOHZ_FULL or idle NOHZ.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.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/1447115762-19734-3-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:37:53 +01:00
Byungchul Park 5954327548 sched/fair: Prepare __update_cpu_load() to handle active tickless
There are some cases where distance between ticks is more than one tick
while the CPU is not idle, e.g. full NOHZ.

However __update_cpu_load() assumes it is the idle tickless case if the
distance between ticks is more than 1, even though it can be the active
tickless case as well. Thus in the active tickless case, updating the CPU
load will not be performed correctly.

Where the current code assumes the load for each tick is zero, this is
(obviously) not true in non-idle tickless case. We can approximately
consider the load ~= this_rq->cpu_load[0] during tickless in non-idle
tickless case.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
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>
Link: http://lkml.kernel.org/r/1444816056-11886-2-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:37:53 +01:00
Peter Zijlstra d937cdc59e sched/fair: Clean up the explanation around decaying load update misses
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>
2015-11-23 09:37:52 +01:00
Dietmar Eggemann 38c6ade2dd sched/fair: Remove empty idle enter and exit functions
Commit cd126afe83 ("sched/fair: Remove rq's runnable avg") got rid of
rq->avg and so there is no need to update it any more when entering or
exiting idle.

Remove the now empty functions idle_{enter|exit}_fair().

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: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yuyang Du <yuyang.du@intel.com>
Link: http://lkml.kernel.org/r/1445342681-17171-1-git-send-email-dietmar.eggemann@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:37:51 +01:00
Arnd Bergmann 89b411081d sched/rt: Hide the push_irq_work_func() declaration
The push_irq_work_func() function is conditionally defined only
when both CONFIG_SMP and HAVE_RT_PUSH_IPI are defined, but the
forward declaration remains visibile without HAVE_RT_PUSH_IPI,
causing a gcc warning in ARM64 allnoconfig:

  kernel/sched/rt.c:68:13: warning: 'push_irq_work_func' declared 'static' but never defined [-Wunused-function]

This changes the code to use the same condition for both the
declaration and the function definition, which gets rid of the
warning.

As Peter Zijlstra, we can possibly get rid of the whole HAVE_RT_PUSH_IPI
thing after:

  8053871d0f ("smp: Fix smp_call_function_single_async() locking")

Until that is done, this patch can be used to avoid the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: b6366f048e ("sched/rt: Use IPI to trigger RT task push migration instead of pulling")
Link: http://lkml.kernel.org/r/3828565.oKfGk7yNIT@wuerfel
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-23 09:25:08 +01:00
Linus Torvalds 051b29f279 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fix from Thomas Gleixner:
 "A single fix to prevent math underflow in the numa balancing code"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/numa: Fix math underflow in task_tick_numa()
2015-11-15 09:35:33 -08:00
Rik van Riel 25b3e5a334 sched/numa: Fix math underflow in task_tick_numa()
The NUMA balancing code implements delays in scanning by
advancing curr->node_stamp beyond curr->se.sum_exec_runtime.

With unsigned math, that creates an underflow, which results
in task_numa_work being queued all the time, even when we
don't want to.

Avoiding the math underflow makes it possible to reduce CPU
overhead in the NUMA balancing code.

Reported-and-tested-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.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: mgorman@suse.de
Link: http://lkml.kernel.org/r/1446756983-28173-2-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-09 16:13:27 +01:00
Linus Torvalds 933425fb00 s390: A bunch of fixes and optimizations for interrupt and time
handling.
 
 PPC: Mostly bug fixes.
 
 ARM: No big features, but many small fixes and prerequisites including:
 - a number of fixes for the arch-timer
 - introducing proper level-triggered semantics for the arch-timers
 - a series of patches to synchronously halt a guest (prerequisite for
   IRQ forwarding)
 - some tracepoint improvements
 - a tweak for the EL2 panic handlers
 - some more VGIC cleanups getting rid of redundant state
 
 x86: quite a few changes:
 
 - support for VT-d posted interrupts (i.e. PCI devices can inject
 interrupts directly into vCPUs).  This introduces a new component (in
 virt/lib/) that connects VFIO and KVM together.  The same infrastructure
 will be used for ARM interrupt forwarding as well.
 
 - more Hyper-V features, though the main one Hyper-V synthetic interrupt
 controller will have to wait for 4.5.  These will let KVM expose Hyper-V
 devices.
 
 - nested virtualization now supports VPID (same as PCID but for vCPUs)
 which makes it quite a bit faster
 
 - for future hardware that supports NVDIMM, there is support for clflushopt,
 clwb, pcommit
 
 - support for "split irqchip", i.e. LAPIC in kernel + IOAPIC/PIC/PIT in
 userspace, which reduces the attack surface of the hypervisor
 
 - obligatory smattering of SMM fixes
 
 - on the guest side, stable scheduler clock support was rewritten to not
 require help from the hypervisor.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM updates from Paolo Bonzini:
 "First batch of KVM changes for 4.4.

  s390:
     A bunch of fixes and optimizations for interrupt and time handling.

  PPC:
     Mostly bug fixes.

  ARM:
     No big features, but many small fixes and prerequisites including:

      - a number of fixes for the arch-timer

      - introducing proper level-triggered semantics for the arch-timers

      - a series of patches to synchronously halt a guest (prerequisite
        for IRQ forwarding)

      - some tracepoint improvements

      - a tweak for the EL2 panic handlers

      - some more VGIC cleanups getting rid of redundant state

  x86:
     Quite a few changes:

      - support for VT-d posted interrupts (i.e. PCI devices can inject
        interrupts directly into vCPUs).  This introduces a new
        component (in virt/lib/) that connects VFIO and KVM together.
        The same infrastructure will be used for ARM interrupt
        forwarding as well.

      - more Hyper-V features, though the main one Hyper-V synthetic
        interrupt controller will have to wait for 4.5.  These will let
        KVM expose Hyper-V devices.

      - nested virtualization now supports VPID (same as PCID but for
        vCPUs) which makes it quite a bit faster

      - for future hardware that supports NVDIMM, there is support for
        clflushopt, clwb, pcommit

      - support for "split irqchip", i.e.  LAPIC in kernel +
        IOAPIC/PIC/PIT in userspace, which reduces the attack surface of
        the hypervisor

      - obligatory smattering of SMM fixes

      - on the guest side, stable scheduler clock support was rewritten
        to not require help from the hypervisor"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (123 commits)
  KVM: VMX: Fix commit which broke PML
  KVM: x86: obey KVM_X86_QUIRK_CD_NW_CLEARED in kvm_set_cr0()
  KVM: x86: allow RSM from 64-bit mode
  KVM: VMX: fix SMEP and SMAP without EPT
  KVM: x86: move kvm_set_irq_inatomic to legacy device assignment
  KVM: device assignment: remove pointless #ifdefs
  KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic
  KVM: x86: zero apic_arb_prio on reset
  drivers/hv: share Hyper-V SynIC constants with userspace
  KVM: x86: handle SMBASE as physical address in RSM
  KVM: x86: add read_phys to x86_emulate_ops
  KVM: x86: removing unused variable
  KVM: don't pointlessly leave KVM_COMPAT=y in non-KVM configs
  KVM: arm/arm64: Merge vgic_set_lr() and vgic_sync_lr_elrsr()
  KVM: arm/arm64: Clean up vgic_retire_lr() and surroundings
  KVM: arm/arm64: Optimize away redundant LR tracking
  KVM: s390: use simple switch statement as multiplexer
  KVM: s390: drop useless newline in debugging data
  KVM: s390: SCA must not cross page boundaries
  KVM: arm: Do not indent the arguments of DECLARE_BITMAP
  ...
2015-11-05 16:26:26 -08:00
Linus Torvalds 69234acee5 Merge branch 'for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
 "The cgroup core saw several significant updates this cycle:

   - percpu_rwsem for threadgroup locking is reinstated.  This was
     temporarily dropped due to down_write latency issues.  Oleg's
     rework of percpu_rwsem which is scheduled to be merged in this
     merge window resolves the issue.

   - On the v2 hierarchy, when controllers are enabled and disabled, all
     operations are atomic and can fail and revert cleanly.  This allows
     ->can_attach() failure which is necessary for cpu RT slices.

   - Tasks now stay associated with the original cgroups after exit
     until released.  This allows tracking resources held by zombies
     (e.g.  pids) and makes it easy to find out where zombies came from
     on the v2 hierarchy.  The pids controller was broken before these
     changes as zombies escaped the limits; unfortunately, updating this
     behavior required too many invasive changes and I don't think it's
     a good idea to backport them, so the pids controller on 4.3, the
     first version which included the pids controller, will stay broken
     at least until I'm sure about the cgroup core changes.

   - Optimization of a couple common tests using static_key"

* 'for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (38 commits)
  cgroup: fix race condition around termination check in css_task_iter_next()
  blkcg: don't create "io.stat" on the root cgroup
  cgroup: drop cgroup__DEVEL__legacy_files_on_dfl
  cgroup: replace error handling in cgroup_init() with WARN_ON()s
  cgroup: add cgroup_subsys->free() method and use it to fix pids controller
  cgroup: keep zombies associated with their original cgroups
  cgroup: make css_set_rwsem a spinlock and rename it to css_set_lock
  cgroup: don't hold css_set_rwsem across css task iteration
  cgroup: reorganize css_task_iter functions
  cgroup: factor out css_set_move_task()
  cgroup: keep css_set and task lists in chronological order
  cgroup: make cgroup_destroy_locked() test cgroup_is_populated()
  cgroup: make css_sets pin the associated cgroups
  cgroup: relocate cgroup_[try]get/put()
  cgroup: move check_for_release() invocation
  cgroup: replace cgroup_has_tasks() with cgroup_is_populated()
  cgroup: make cgroup->nr_populated count the number of populated css_sets
  cgroup: remove an unused parameter from cgroup_task_migrate()
  cgroup: fix too early usage of static_branch_disable()
  cgroup: make cgroup_update_dfl_csses() migrate all target processes atomically
  ...
2015-11-05 14:51:32 -08:00
Linus Torvalds 53528695ff Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler changes from Ingo Molnar:
 "The main changes in this cycle were:

   - sched/fair load tracking fixes and cleanups (Byungchul Park)

   - Make load tracking frequency scale invariant (Dietmar Eggemann)

   - sched/deadline updates (Juri Lelli)

   - stop machine fixes, cleanups and enhancements for bugs triggered by
     CPU hotplug stress testing (Oleg Nesterov)

   - scheduler preemption code rework: remove PREEMPT_ACTIVE and related
     cleanups (Peter Zijlstra)

   - Rework the sched_info::run_delay code to fix races (Peter Zijlstra)

   - Optimize per entity utilization tracking (Peter Zijlstra)

   - ... misc other fixes, cleanups and smaller updates"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
  sched: Don't scan all-offline ->cpus_allowed twice if !CONFIG_CPUSETS
  sched: Move cpu_active() tests from stop_two_cpus() into migrate_swap_stop()
  sched: Start stopper early
  stop_machine: Kill cpu_stop_threads->setup() and cpu_stop_unpark()
  stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark()
  stop_machine: Change cpu_stop_queue_two_works() to rely on stopper->enabled
  stop_machine: Introduce __cpu_stop_queue_work() and cpu_stop_queue_two_works()
  stop_machine: Ensure that a queued callback will be called before cpu_stop_park()
  sched/x86: Fix typo in __switch_to() comments
  sched/core: Remove a parameter in the migrate_task_rq() function
  sched/core: Drop unlikely behind BUG_ON()
  sched/core: Fix task and run queue sched_info::run_delay inconsistencies
  sched/numa: Fix task_tick_fair() from disabling numa_balancing
  sched/core: Add preempt_count invariant check
  sched/core: More notrace annotations
  sched/core: Kill PREEMPT_ACTIVE
  sched/core, sched/x86: Kill thread_info::saved_preempt_count
  sched/core: Simplify preempt_count tests
  sched/core: Robustify preemption leak checks
  sched/core: Stop setting PREEMPT_ACTIVE
  ...
2015-11-03 18:03:50 -08:00
Ingo Molnar e4340bbb07 Merge branch 'linus' into core/rcu, to fix up a semantic conflict
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-28 13:17:20 +01:00
Peter Zijlstra 0aaafaabfc sched/core: Add missing lockdep_unpin() annotations
Luca and Wanpeng reported two missing annotations that led to
false lockdep complaints. Add the missing annotations.

Reported-by: Luca Abeni <luca.abeni@unitn.it>
Reported-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@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>
Fixes: cbce1a6867 ("sched,lockdep: Employ lock pinning")
Link: http://lkml.kernel.org/r/20151023095008.GY17308@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-23 12:02:10 +02:00
Oleg Nesterov e73e85f059 sched: Don't scan all-offline ->cpus_allowed twice if !CONFIG_CPUSETS
If CONFIG_CPUSETS=n then "case cpuset" changes the state and runs
the already failed for_each_cpu() loop again for no reason.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151010185315.GA24100@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:25:57 +02:00
Peter Zijlstra 62694cd513 sched: Move cpu_active() tests from stop_two_cpus() into migrate_swap_stop()
The cpu_active() tests are not fundamentally part of stop_two_cpus(),
move then into the scheduler where they belong.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:25:56 +02:00
Peter Zijlstra 07f06cb3b5 sched: Start stopper early
Ensure the stopper thread is active 'early', because the load balancer
pretty much assumes that its available. And when 'online && active' the
load-balancer is fully available.

Not only the numa balancing stop_two_cpus() caller relies on it, but
also the self migration stuff does, and at CPU_ONLINE time the cpu
really is 'free' to run anything.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151009160054.GA10176@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:25:55 +02:00
Ingo Molnar 6af597de62 Merge branch 'sched/urgent' into sched/core, to pick up fixes and resolve conflicts
Conflicts:
	kernel/sched/fair.c

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:18:16 +02:00
Luca Abeni 5aa5050787 sched/deadline: Fix migration of SCHED_DEADLINE tasks
Commit:

  9d51426242 ("sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target")

broke select_task_rq_dl() and find_lock_later_rq(), because it introduced
a comparison between the local task's deadline and dl.earliest_dl.curr of
the remote queue.

However, if the remote runqueue does not contain any SCHED_DEADLINE
task its earliest_dl.curr is 0 (always smaller than the deadline of
the local task) and the remote runqueue is not selected for pushing.

As a result, if an application creates multiple SCHED_DEADLINE
threads, they will never be pushed to runqueues that do not already
contain SCHED_DEADLINE tasks.

This patch fixes the issue by checking if dl.dl_nr_running == 0.

Signed-off-by: Luca Abeni <luca.abeni@unitn.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@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: Wanpeng Li <wanpeng.li@linux.intel.com>
Fixes: 9d51426242 ("sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target")
Link: http://lkml.kernel.org/r/1444982781-15608-1-git-send-email-luca.abeni@unitn.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:13:36 +02:00
Frederic Weisbecker 0baabb385e nohz: Revert "nohz: Set isolcpus when nohz_full is set"
This reverts:

  8cb9764fc8 ("nohz: Set isolcpus when nohz_full is set")

We assumed that full-nohz users always want scheduler isolation on full
dynticks CPUs, therefore we included full-nohz CPUs on cpu_isolated_map.

This means that tasks run by default on CPUs outside the nohz_full range
unless their affinity is explicity overwritten.

This suits pure isolation workloads but when the machine is needed to
run common workloads, the available sets of CPUs to run common tasks
becomes reduced.

We reach an extreme case when CONFIG_NO_HZ_FULL_ALL is enabled as it
leaves only CPU 0 for non-isolation tasks, which makes people think that
their supercomputer regressed to 90's UP - which is true in a sense.

Some full-nohz users appear to be interested in running normal workloads
either before or after an isolation workload. Full-nohz isn't optimized
toward normal workloads but it's still better than UP performance.

We are reaching a limitation in kernel presets here. Lets revert this
cpu_isolated_map inclusion and let userspace do its own scheduler
isolation using cpusets or explicit affinity settings.

Reported-by: Ingo Molnar <mingo@kernel.org>
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Link: http://lkml.kernel.org/r/1444663283-30068-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:13:36 +02:00
Yuyang Du 3e386d56ba sched/fair: Update task group's load_avg after task migration
When cfs_rq has cfs_rq->removed_load_avg set (when a task migrates from
this cfs_rq), we need to update its contribution to the group's load_avg.

This should not increase tg's update too much, because in most cases, the
cfs_rq has already decayed its load_avg.

Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dietmar Eggemann <dietmar.eggemann@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>
Link: http://lkml.kernel.org/r/1444699103-20272-2-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:13:35 +02:00
Yuyang Du fde7d22e01 sched/fair: Fix overly small weight for interactive group entities
Commit:

  9d89c257df ("sched/fair: Rewrite runnable load and utilization average tracking")

led to an overly small weight for interactive group entities. The bad case
can be easily reproduced when a number of CPU hogs compete for the CPUs
at the same time (thanks to Mike). This is largly because the task group's
load average tracking cross CPUs lags behind the real changes.

To fix this we accelerate the group share distribution process by using
the load.weight of the cfs_rq. This may increase the entire group's
share, but we have to do so to protect the (fragile) interactive
tasks, especially from CPU hogs.

Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dietmar Eggemann <dietmar.eggemann@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>
Link: http://lkml.kernel.org/r/1444699103-20272-1-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-20 10:13:34 +02:00
Ingo Molnar c13dc31adb Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU updates from Paul E. McKenney:

  - Miscellaneous fixes. (Paul E. McKenney, Boqun Feng, Oleg Nesterov, Patrick Marlier)

  - Improvements to expedited grace periods. (Paul E. McKenney)

  - Performance improvements to and locktorture tests for percpu-rwsem.
    (Oleg Nesterov, Paul E. McKenney)

  - Torture-test changes. (Paul E. McKenney, Davidlohr Bueso)

  - Documentation updates. (Paul E. McKenney)

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-19 10:09:54 +02:00
Tejun Heo 2e91fa7f6d cgroup: keep zombies associated with their original cgroups
cgroup_exit() is called when a task exits and disassociates the
exiting task from its cgroups and half-attach it to the root cgroup.
This is unnecessary and undesirable.

No controller actually needs an exiting task to be disassociated with
non-root cgroups.  Both cpu and perf_event controllers update the
association to the root cgroup from their exit callbacks just to keep
consistent with the cgroup core behavior.

Also, this disassociation makes it difficult to track resources held
by zombies or determine where the zombies came from.  Currently, pids
controller is completely broken as it uncharges on exit and zombies
always escape the resource restriction.  With cgroup association being
reset on exit, fixing it is pretty painful.

There's no reason to reset cgroup membership on exit.  The zombie can
be removed from its css_set so that it doesn't show up on
"cgroup.procs" and thus can't be migrated or interfere with cgroup
removal.  It can still pin and point to the css_set so that its cgroup
membership is maintained.  This patch makes cgroup core keep zombies
associated with their cgroups at the time of exit.

* Previous patches decoupled populated_cnt tracking from css_set
  lifetime, so a dying task can be simply unlinked from its css_set
  while pinning and pointing to the css_set.  This keeps css_set
  association from task side alive while hiding it from "cgroup.procs"
  and populated_cnt tracking.  The css_set reference is dropped when
  the task_struct is freed.

* ->exit() callback no longer needs the css arguments as the
  associated css never changes once PF_EXITING is set.  Removed.

* cpu and perf_events controllers no longer need ->exit() callbacks.
  There's no reason to explicitly switch away on exit.  The final
  schedule out is enough.  The callbacks are removed.

* On traditional hierarchies, nothing changes.  "/proc/PID/cgroup"
  still reports "/" for all zombies.  On the default hierarchy,
  "/proc/PID/cgroup" keeps reporting the cgroup that the task belonged
  to at the time of exit.  If the cgroup gets removed before the task
  is reaped, " (deleted)" is appended.

v2: Build brekage due to missing dummy cgroup_free() when
    !CONFIG_CGROUP fixed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
2015-10-15 16:41:53 -04:00
Daniel Bristot de Oliveira 9babcd7929 sched, tracing: Stop/start critical timings around the idle=poll idle loop
When using idle=poll, the preemptoff tracer is always showing
the idle task as the culprit for long latencies. That happens
because critical timings are not stopped before idle loop. This
patch stops critical timings before entering the idle loop,
starting it again after the idle loop.

This problem does not affect the irqsoff tracer because
interruptions are enabled before entering the idle loop.

Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Reviewed-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.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>
Link: http://lkml.kernel.org/r/10fc3705874aef11dbe152a068b591a7be1899b4.1444314899.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-12 09:45:25 +02:00
Davidlohr Bueso 84778472e1 sched: Export sched_setscheduler_nocheck
The new locktorture rtmutex_lock tests exercise priority boosting, which
means that they need to set some tasks to real-time priority.  To do this,
they use sched_setscheduler_nocheck().  However, this is not exported to
modules, which results in the following error when building locktorture
as a module:

ERROR: "sched_setscheduler_nocheck" [kernel/locking/locktorture.ko] undefined!

This commit therefore adds an EXPORT_SYMBOL_GPL() to allow this function
to be invoked from locktorture when built as a module.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-10-06 11:07:54 -07:00
xiaofeng.yan 5a4fd03685 sched/core: Remove a parameter in the migrate_task_rq() function
The parameter "int next_cpu" in the following function is unused:

  migrate_task_rq(struct task_struct *p, int next_cpu)

Remove it.

Signed-off-by: xiaofeng.yan <yanxiaofeng@inspur.com>
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: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1442991360-31945-1-git-send-email-yanxiaofeng@inspur.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:23 +02:00
Geliang Tang ce03e4137b sched/core: Drop unlikely behind BUG_ON()
(1) For !CONFIG_BUG cases, the bug call is a no-op, so we couldn't care
    less and the change is ok.

(2) PPC and MIPS, which HAVE_ARCH_BUG_ON, do not rely on branch predictions
    as it seems to be pointless [1] and thus callers should not be trying to
    push an optimization in the first place.

(3) For CONFIG_BUG and !HAVE_ARCH_BUG_ON cases, BUG_ON() contains an
    unlikely compiler flag already.

Hence, we can drop unlikely behind BUG_ON().

  [1] http://lkml.iu.edu/hypermail/linux/kernel/1101.3/02289.html

Signed-off-by: Geliang Tang <geliangtang@163.com>
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: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/6fa7125979f98bbeac26e268271769b6ca935c8d.1444051018.git.geliangtang@163.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:22 +02:00
Peter Zijlstra 1de64443d7 sched/core: Fix task and run queue sched_info::run_delay inconsistencies
Mike Meyer reported the following bug:

> During evaluation of some performance data, it was discovered thread
> and run queue run_delay accounting data was inconsistent with the other
> accounting data that was collected.  Further investigation found under
> certain circumstances execution time was leaking into the task and
> run queue accounting of run_delay.
>
> Consider the following sequence:
>
>     a. thread is running.
>     b. thread moves beween cgroups, changes scheduling class or priority.
>     c. thread sleeps OR
>     d. thread involuntarily gives up cpu.
>
> a. implies:
>
>     thread->sched_info.last_queued = 0
>
> a. and b. results in the following:
>
>     1. dequeue_task(rq, thread)
>
>            sched_info_dequeued(rq, thread)
>                delta = 0
>
>                sched_info_reset_dequeued(thread)
>                    thread->sched_info.last_queued = 0
>
>                thread->sched_info.run_delay += delta
>
>     2. enqueue_task(rq, thread)
>
>            sched_info_queued(rq, thread)
>
>                /* thread is still on cpu at this point. */
>                thread->sched_info.last_queued = task_rq(thread)->clock;
>
> c. results in:
>
>     dequeue_task(rq, thread)
>
>         sched_info_dequeued(rq, thread)
>
>             /* delta is execution time not run_delay. */
>             delta = task_rq(thread)->clock - thread->sched_info.last_queued
>
>         sched_info_reset_dequeued(thread)
>             thread->sched_info.last_queued = 0
>
>         thread->sched_info.run_delay += delta
>
>     Since thread was running between enqueue_task(rq, thread) and
>     dequeue_task(rq, thread), the delta above is really execution
>     time and not run_delay.
>
> d. results in:
>
>     __sched_info_switch(thread, next_thread)
>
>         sched_info_depart(rq, thread)
>
>             sched_info_queued(rq, thread)
>
>                 /* last_queued not updated due to being non-zero */
>                 return
>
>     Since thread was running between enqueue_task(rq, thread) and
>     __sched_info_switch(thread, next_thread), the execution time
>     between enqueue_task(rq, thread) and
>     __sched_info_switch(thread, next_thread) now will become
>     associated with run_delay due to when last_queued was last updated.
>

This alternative patch solves the problem by not calling
sched_info_{de,}queued() in {de,en}queue_task(). Therefore the
sched_info state is preserved and things work as expected.

By inlining the {de,en}queue_task() functions the new condition
becomes (mostly) a compile-time constant and we'll not emit any new
branch instructions.

It even shrinks the code (due to inlining {en,de}queue_task()):

$ size defconfig-build/kernel/sched/core.o defconfig-build/kernel/sched/core.o.orig
   text    data     bss     dec     hex filename
  64019   23378    2344   89741   15e8d defconfig-build/kernel/sched/core.o
  64149   23378    2344   89871   15f0f defconfig-build/kernel/sched/core.o.orig

Reported-by: Mike Meyer <Mike.Meyer@Teradata.com>
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: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150930154413.GO3604@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:22 +02:00
Srikar Dronamraju b52da86e0a sched/numa: Fix task_tick_fair() from disabling numa_balancing
If static branch 'sched_numa_balancing' is enabled, it should kickstart
NUMA balancing through task_tick_numa(). However the following commit:

  2a595721a1 ("sched/numa: Convert sched_numa_balancing to a static_branch")

erroneously disables this.

Fix this anomaly by enabling task_tick_numa() when the static branch
'sched_numa_balancing' is enabled.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1443752305-27413-1-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:21 +02:00
Peter Zijlstra e2bf1c4b17 sched/core: Add preempt_count invariant check
Ingo requested I keep my debug check for the preempt_count invariant.

Requested-by: Ingo Molnar <mingo@kernel.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: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:20 +02:00
Peter Zijlstra 499d79559f sched/core: More notrace annotations
preempt_schedule_common() is marked notrace, but it does not use
_notrace() preempt_count functions and __schedule() is also not marked
notrace, which means that its perfectly possible to end up in the
tracer from preempt_schedule_common().

Steve says:

  | Yep, there's some history to this. This was originally the issue that
  | caused function tracing to go into infinite recursion. But now we have
  | preempt_schedule_notrace(), which is used by the function tracer, and
  | that function must not be traced till preemption is disabled.
  |
  | Now if function tracing is running and we take an interrupt when
  | NEED_RESCHED is set, it calls
  |
  |   preempt_schedule_common() (not traced)
  |
  | But then that calls preempt_disable() (traced)
  |
  | function tracer calls preempt_disable_notrace() followed by
  | preempt_enable_notrace() which will see NEED_RESCHED set, and it will
  | call preempt_schedule_notrace(), which stops the recursion, but
  | still calls __schedule() here, and that means when we return, we call
  | the __schedule() from preempt_schedule_common().
  |
  | That said, I prefer this patch. Preemption is disabled before calling
  | __schedule(), and we get rid of a one round recursion with the
  | scheduler.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:20 +02:00
Peter Zijlstra da7142e2ed sched/core: Simplify preempt_count tests
Since we stopped setting PREEMPT_ACTIVE, there is no need to mask it
out of preempt_count() tests.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:17 +02:00
Peter Zijlstra 1dc0fffc48 sched/core: Robustify preemption leak checks
When we warn about a preempt_count leak; reset the preempt_count to
the known good value such that the problem does not ripple forward.

This is most important on x86 which has a per cpu preempt_count that is
not saved/restored (after this series). So if you schedule with an
invalid (!2*PREEMPT_DISABLE_OFFSET) preempt_count the next task is
messed up too.

Enforcing this invariant limits the borkage to just the one task.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:17 +02:00
Peter Zijlstra 3d8f74dd4c sched/core: Stop setting PREEMPT_ACTIVE
Now that nothing tests for PREEMPT_ACTIVE anymore, stop setting it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:16 +02:00
Peter Zijlstra c73464b1c8 sched/core: Fix trace_sched_switch()
__trace_sched_switch_state() is the last remaining PREEMPT_ACTIVE
user, move trace_sched_switch() from prepare_task_switch() to
__schedule() and propagate the @preempt argument.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-10-06 17:08:15 +02:00