[PATCH 2/3] timer: Check thread timers only when there are active thread timers

Jason Low
2015-08-26T03:18:33Z

The fastpath_timer_check() contains logic to check for if any timers
are set by checking if !task_cputime_zero(). Similarly, we can do this
before calling check_thread_timers(). In the case where there
are only process-wide timers, this will skip all the computations for
the per-thread timers when there are no per-thread timers.

Signed-off-by: Jason Low <jason.low2@hp.com>
---
kernel/time/posix-cpu-timers.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 02596ff..535bef5 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1168,11 +1168,13 @@ void run_posix_cpu_timers(struct task_struct *tsk)
if (!lock_task_sighand(tsk, &flags))
return;
/*
- * Here we take off tsk->signal->cpu_timers[N] and
- * tsk->cpu_timers[N] all the timers that are firing, and
- * put them on the firing list.
+ * If there are active per-thread timers, take off
+ * tsk->signal->cpu_timers[N] and tsk->cpu_timers[N] all the
+ * timers that are firing, and put them on the firing list.
*/
- check_thread_timers(tsk, &firing);
+ if (!task_cputime_zero(&tsk->cputime_expires))
+ check_thread_timers(tsk, &firing);
+
/*
* If there are any active process wide timers (POSIX 1.b, itimers,
* RLIMIT_CPU) cputimer must be running.
--
1.7.2.5