Messages in this thread | | | Date | Wed, 28 Apr 2010 15:09:16 -0700 | Subject | Re: [PATCH 6/8] PM: Add suspend blocking work. | From | Arve Hjønnevåg <> |
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2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>: > On Wednesday 28 April 2010, Oleg Nesterov wrote: >> On 04/27, Arve Hjønnevåg wrote: >> > >> > Allow work to be queued that will block suspend while it is pending >> > or executing. To get the same functionality in the calling code often >> > requires a separate suspend_blocker for pending and executing work, or >> > additional state and locking. This implementation does add additional >> > state and locking, but this can be removed later if we add support for >> > suspend blocking work to the core workqueue code. >> >> I think this patch is fine. >> >> Just one silly question, >> >> > +int queue_suspend_blocking_work(struct workqueue_struct *wq, >> > + struct suspend_blocking_work *work) >> > +{ >> > + int ret; >> > + unsigned long flags; >> > + >> > + spin_lock_irqsave(&work->lock, flags); >> > + suspend_block(&work->suspend_blocker); >> > + ret = queue_work(wq, &work->work); >> > + if (ret) >> > + work->active++; >> >> why not >> >> ret = queue_work(wq, &work->work); >> if (ret) { >> suspend_block(&work->suspend_blocker); >> work->active++; >> } >> >> ? >> >> Afaics, we can't race with work->func() doing unblock, we hold work-lock. >> And this way the code looks more clear. > > Agreed. Arve, any objections to doing that? >
I need to fix the race, but I can easily fix it in cancel_suspend_blocking_work_sync instead. If the suspend blocker is active for a long time, and DEBUG_SUSPEND_BLOCKER is enabled, we can tell if the work is constantly re-queued or if the workqueue is stuck.
>> Sorry, I had no chance to read the previous patches. After the quick look >> at 1/8 I think it is OK to call suspend_block() twice, but still... > > It is. > >> Or I missed something? Just curious. >> >> >> Hmm... actually, queue_work() can also fail if we race with cancel_ which >> temporary sets WORK_STRUCT_PENDING. In that case suspend_block() won't >> be paired by unblock ? >> >> >> > +int schedule_suspend_blocking_work(struct suspend_blocking_work *work) >> > +{ >> > ... >> > + ret = schedule_work(&work->work); >> >> Off-topic. We should probably export keventd_wq to avoid the duplications >> like this. > > Please see my reply to Tejun. :-) > > Rafael >
-- Arve Hjønnevåg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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