The patch titled
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
has been added to the -mm tree. Its filename is
posix-cpu-timers-reset-expire-cache-when-no-timer-is-running.patch
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Subject: From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
When process delete cpu timer or timer expires we do not clear
expiration cache sig->cputimer_expires. This create situation when in
fastpath_timer_check() we _on_ cputimer (together with loop on all
threads) just to turn in off in check_process_timers(). We not
necessary go to slowpath and not necessary loop on all threads in
fastpath - and this is repeated on every tick.
To fix we zero sig->cputimer_expires in stop_process_timers().
Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
Cc: Spencer Candland <spencer@xxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/posix-cpu-timers.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff -puN kernel/posix-cpu-timers.c~posix-cpu-timers-reset-expire-cache-when-no-timer-is-running kernel/posix-cpu-timers.c
--- a/kernel/posix-cpu-timers.c~posix-cpu-timers-reset-expire-cache-when-no-timer-is-running
+++ a/kernel/posix-cpu-timers.c
@@ -1060,9 +1060,9 @@ static void check_thread_timers(struct t
}
}
-static void stop_process_timers(struct task_struct *tsk)
+static void stop_process_timers(struct signal_struct *sig)
{
- struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+ struct thread_group_cputimer *cputimer = &sig->cputimer;
unsigned long flags;
if (!cputimer->running)
@@ -1071,6 +1071,10 @@ static void stop_process_timers(struct t
spin_lock_irqsave(&cputimer->lock, flags);
cputimer->running = 0;
spin_unlock_irqrestore(&cputimer->lock, flags);
+
+ sig->cputime_expires.prof_exp = cputime_zero;
+ sig->cputime_expires.virt_exp = cputime_zero;
+ sig->cputime_expires.sched_exp = 0;
}
static u32 onecputick;
@@ -1131,7 +1135,7 @@ static void check_process_timers(struct
list_empty(&timers[CPUCLOCK_VIRT]) &&
cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
list_empty(&timers[CPUCLOCK_SCHED])) {
- stop_process_timers(tsk);
+ stop_process_timers(sig);
return;
}
_
Patches currently in -mm which might be from sgruszka@xxxxxxxxxx are
linux-next.patch
itimers-fix-racy-writes-to-cpu_itimer-fields.patch
posix-cpu-timers-optimize-and-document-timer_create-callback.patch
posix-cpu-timers-reset-expire-cache-when-no-timer-is-running.patch
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