From e2a43807d963d7c45badb5f3b2a2349f4afc93eb Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 3 Jul 2009 08:44:44 -0500 Subject: [PATCH] posix-timers: Avoid wakeups when no timers are active Waking the thread even when no timers are scheduled is useless. Signed-off-by: Thomas Gleixner --- kernel/posix-cpu-timers.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index a778d1b97669..1764090d598d 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -1274,6 +1274,21 @@ wait_to_die: return 0; } +static inline int __fastpath_timer_check(struct task_struct *tsk) +{ + /* tsk == current, ensure it is safe to use ->signal/sighand */ + if (unlikely(tsk->exit_state)) + return 0; + + if (!task_cputime_zero(&tsk->cputime_expires)) + return 1; + + if (!task_cputime_zero(&tsk->signal->cputime_expires)) + return 1; + + return 0; +} + void run_posix_cpu_timers(struct task_struct *tsk) { unsigned long cpu = smp_processor_id(); @@ -1286,7 +1301,7 @@ void run_posix_cpu_timers(struct task_struct *tsk) tasklist = per_cpu(posix_timer_tasklist, cpu); /* check to see if we're already queued */ - if (!tsk->posix_timer_list) { + if (!tsk->posix_timer_list && __fastpath_timer_check(tsk)) { get_task_struct(tsk); if (tasklist) { tsk->posix_timer_list = tasklist; @@ -1298,9 +1313,9 @@ void run_posix_cpu_timers(struct task_struct *tsk) tsk->posix_timer_list = tsk; } per_cpu(posix_timer_tasklist, cpu) = tsk; + + wake_up_process(per_cpu(posix_timer_task, cpu)); } - /* XXX signal the thread somehow */ - wake_up_process(per_cpu(posix_timer_task, cpu)); } /*