The patch titled
Subject: posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()
has been added to the -mm tree. Its filename is
posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule.patch
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------------------------------------------------------
From: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Subject: posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()
In order to arm the next timer to schedule, we take a sample of the
current process or thread cputime.
If the task is dying though, we don't arm anything but we cache the
remaining timer expiration delta for further reads.
Something similar is performed in posix_cpu_timer_get() but here we forget
to take the process wide cputime sample before caching it.
As a result we are storing random stack content, leading every further
reads of that timer to return junk values.
Fix this by taking the appropriate sample in the case of process wide
timers.
Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reported-by: Chen Gang <gang.chen@xxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Chen Gang <gang.chen@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/posix-cpu-timers.c | 1 +
1 file changed, 1 insertion(+)
diff -puN kernel/posix-cpu-timers.c~posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule kernel/posix-cpu-timers.c
--- a/kernel/posix-cpu-timers.c~posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule
+++ a/kernel/posix-cpu-timers.c
@@ -1062,6 +1062,7 @@ void posix_cpu_timer_schedule(struct k_i
* not yet reaped. Take this opportunity to
* drop our task ref.
*/
+ cpu_timer_sample_group(timer->it_clock, p, &now);
clear_dead_task(timer, now);
goto out_unlock;
}
_
Patches currently in -mm which might be from fweisbec@xxxxxxxxx are
linux-next.patch
posix_cpu_timer-consolidate-expiry-time-type.patch
posix_cpu_timers-consolidate-timer-list-cleanups.patch
posix_cpu_timers-consolidate-expired-timers-check.patch
selftests-add-basic-posix-timers-selftests.patch
posix-timers-correctly-get-dying-task-time-sample-in-posix_cpu_timer_schedule.patch
posix_timers-fix-racy-timer-delta-caching-on-task-exit.patch
posix_timers-remove-dead-task-timer-expiry-caching.patch
mm-trace-filemap-add-and-del.patch
mm-trace-filemap-add-and-del-v2.patch
printk-tracing-rework-console-tracing.patch
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