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authorFrederic Weisbecker <fweisbec@gmail.com>2013-06-28 00:06:43 +0000
committerFrederic Weisbecker <fweisbec@gmail.com>2013-07-03 16:20:20 +0200
commit76cdcdd979ce00f5037804d73da583fb488ec1b2 (patch)
treec0959aaea64748a44f99e1e9ffef6b8eee179c53 /kernel
parent0bc4b0cf15708fca04095232c4e448634e94d029 (diff)
posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()
In order to re-arm a timer after it fired, 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. This probably doesn't matter much in practice because, at this stage, the thread is the last one in the group and we reached exit_notify(). This implies that we called exit_itimers() and there should be no more timers to handle for that task. So this is likely dead code anyway but let's fix the current logic and the warning that came along: kernel/posix-cpu-timers.c: In function 'posix_cpu_timer_schedule': kernel/posix-cpu-timers.c:1127: warning: 'now' may be used uninitialized in this function Then we can start to think further about cleaning up that code. Reported-by: Andrew Morton <akpm@linux-foundation.org> Reported-by: Chen Gang <gang.chen@asianux.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Chen Gang <gang.chen@asianux.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Olivier Langlois <olivier@trillion01.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/posix-cpu-timers.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 92a4fbf44f86..4ebd8ad07c66 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1097,6 +1097,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
* 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;
}