Messages in this thread | | | Subject | Re: sched: race between deactivate and switch sched_info accounting? | From | Peter Zijlstra <> | Date | Sat, 10 Oct 2009 08:37:40 +0200 |
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On Fri, 2009-10-09 at 19:40 -0700, Paul Turner wrote:
This looks very funny, I would expect that whoever does activate() on that task to do the sched_info*() muck?
The below patch looks very asymmetric in that regard.
> It's possible for our previously de-activated task to be re-activated by a > remote cpu during lock balancing. We have to account for this manually > since prev == next, yet the task just went through dequeue accounting. > > Signed-off-by: Paul Turner <pjt@google.com> > --- > kernel/sched.c | 15 ++++++++++++--- > 1 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index ee61f45..6445d9d 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -5381,7 +5381,7 @@ asmlinkage void __sched schedule(void) > struct task_struct *prev, *next; > unsigned long *switch_count; > struct rq *rq; > - int cpu; > + int cpu, deactivated_prev = 0; > > need_resched: > preempt_disable(); > @@ -5406,8 +5406,10 @@ need_resched_nonpreemptible: > if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { > if (unlikely(signal_pending_state(prev->state, prev))) > prev->state = TASK_RUNNING; > - else > + else { > deactivate_task(rq, prev, 1); > + deactivated_prev = 1; > + } > switch_count = &prev->nvcsw; > } > > @@ -5434,8 +5436,15 @@ need_resched_nonpreemptible: > */ > cpu = smp_processor_id(); > rq = cpu_rq(cpu); > - } else > + } else { > + /* > + * account for our previous task being re-activated by a > + * remote cpu. > + */ > + if (unlikely(deactivated_prev)) > + sched_info_switch(prev, prev); > spin_unlock_irq(&rq->lock); > + } > > post_schedule(rq); >
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