Messages in this thread | | | Date | Wed, 22 Jun 2011 11:24:30 +0200 | From | Tejun Heo <> | Subject | Re: [RFC][PATCH 2/3] sched, workqueue: Move WQ-sleeper wakeup |
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Hello, Peter.
On Wed, Jun 22, 2011 at 01:34:46AM +0200, Peter Zijlstra wrote: > -/** > * wake_up_process - Wake up a specific process > * @p: The process to be woken up. > * > @@ -4215,6 +4181,19 @@ static inline void sched_submit_work(voi > > if (tsk->state && !(preempt_count() & PREEMPT_ACTIVE)) { > /* > + * If a worker went to sleep, notify and ask workqueue > + * whether it wants to wake up a task to maintain > + * concurrency. > + */ > + if (tsk->flags & PF_WQ_WORKER) { > + struct task_struct *to_wakeup; > + > + to_wakeup = wq_worker_sleeping(tsk, smp_processor_id()); > + if (to_wakeup) > + wake_up_process(to_wakeup); > + } > + > + /*
Preemption could still be enabled here, right? What prevents preemtion kicking after wq_worker_sleeping() and do it again thus breaking nr_running tracking.
> * If we are going to sleep and we have plugged IO > * queued, make sure to submit it to avoid deadlocks. > */ > @@ -4256,19 +4235,6 @@ asmlinkage void __sched schedule(void) > } else { > deactivate_task(rq, prev, DEQUEUE_SLEEP); > prev->on_rq = 0; > - > - /* > - * If a worker went to sleep, notify and ask workqueue > - * whether it wants to wake up a task to maintain > - * concurrency. > - */ > - if (prev->flags & PF_WQ_WORKER) { > - struct task_struct *to_wakeup; > - > - to_wakeup = wq_worker_sleeping(prev, cpu); > - if (to_wakeup) > - try_to_wake_up_local(to_wakeup); > - }
Similarly, the if the 'if {}' part of the above if/else is taken, the task never goes to sleep and nr_running will again be broken.
-- tejun
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