[patch] sched: fix/add missing update_rq_clock() calls

Mike Galbraith
2009-11-12T10:07:48Z

sched: fix/add missing update_rq_clock() calls.

kthread_bind(), migrate_task() and sched_fork were missing updates, and
try_to_wake_up() was updating after having already used the stale clock.

Aside from preventing potential latency hits, there' a side benefit in that
early boot printk time stamps become monotonic.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>

---
kernel/sched.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

Index: linux-2.6.32.git/kernel/sched.c
===================================================================
--- linux-2.6.32.git.orig/kernel/sched.c
+++ linux-2.6.32.git/kernel/sched.c
@@ -2019,6 +2019,7 @@ void kthread_bind(struct task_struct *p,
}

spin_lock_irqsave(&rq->lock, flags);
+ update_rq_clock(rq);
set_task_cpu(p, cpu);
p->cpus_allowed = cpumask_of_cpu(cpu);
p->rt.nr_cpus_allowed = 1;
@@ -2117,6 +2118,7 @@ migrate_task(struct task_struct *p, int
* it is sufficient to simply update the task's cpu field.
*/
if (!p->se.on_rq && !task_running(rq, p)) {
+ update_rq_clock(rq);
set_task_cpu(p, dest_cpu);
return 0;
}
@@ -2378,14 +2380,15 @@ static int try_to_wake_up(struct task_st
task_rq_unlock(rq, &flags);

cpu = p->sched_class->select_task_rq(p, SD_BALANCE_WAKE, wake_flags);
- if (cpu != orig_cpu)
+ if (cpu != orig_cpu) {
+ local_irq_save(flags);
+ rq = cpu_rq(cpu);
+ update_rq_clock(rq);
set_task_cpu(p, cpu);
-
+ local_irq_restore(flags);
+ }
rq = task_rq_lock(p, &flags);

- if (rq != orig_rq)
- update_rq_clock(rq);
-
WARN_ON(p->state != TASK_WAKING);
cpu = task_cpu(p);

@@ -2558,6 +2561,7 @@ static void __sched_fork(struct task_str
void sched_fork(struct task_struct *p, int clone_flags)
{
int cpu = get_cpu();
+ unsigned long flags;

__sched_fork(p);

@@ -2594,7 +2598,10 @@ void sched_fork(struct task_struct *p, i
#ifdef CONFIG_SMP
cpu = p->sched_class->select_task_rq(p, SD_BALANCE_FORK, 0);
#endif
+ local_irq_save(flags);
+ update_rq_clock(cpu_rq(cpu));
set_task_cpu(p, cpu);
+ local_irq_restore(flags);

#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (likely(sched_info_on()))