From fb9d645bcacaced10a18726bd8c0fface2bef5bb 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 commit 4aef9893f48ad8905a35b2fbe2cc78662c0fa441 in tip. Waking the thread even when no timers are scheduled is useless. Signed-off-by: Thomas Gleixner Signed-off-by: Paul Gortmaker --- kernel/posix-cpu-timers.c | 21 ++++++++++++++++++--- 1 files changed, 18 insertions(+), 3 deletions(-) diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index a73d9f0..892f63b 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -1517,6 +1517,21 @@ 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(); @@ -1529,7 +1544,7 @@ 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; @@ -1541,9 +1556,9 @@ 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)); } /* -- 1.7.0.4