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From fb9d645bcacaced10a18726bd8c0fface2bef5bb Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
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 <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
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
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