Messages in this thread | | | Date | Thu, 13 Nov 2003 22:16:51 +1100 | From | Nick Piggin <> | Subject | Re: AS spin lock bugs |
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Jens Axboe wrote:
>On Thu, Nov 13 2003, Jens Axboe wrote: > >>On Thu, Nov 13 2003, Nick Piggin wrote: >> >>> >>>Jens Axboe wrote: >>> >>> >>>>On Thu, Nov 13 2003, Jens Axboe wrote: >>>> >>>> >>>>>@@ -959,12 +960,12 @@ >>>>> if (!aic) >>>>> return; >>>>> >>>>>- spin_lock(&aic->lock); >>>>>+ spin_lock_irqsave(&aic->lock, flags); >>>>> if (arq->is_sync == REQ_SYNC) { >>>>> set_bit(AS_TASK_IORUNNING, &aic->state); >>>>> aic->last_end_request = jiffies; >>>>> } >>>>>- spin_unlock(&aic->lock); >>>>>+ spin_unlock_irqrestore(&aic->lock, flags); >>>>> >>>>> put_io_context(arq->io_context); >>>>>} >>>>> >>>>> >>>>BTW, this looks bogus. Why do you need any locking there? >>>> >>>> >>>To prevent a request completion on another queue on another CPU from >>>racing with request insertion: last_end_request is undefined if the >>>flag is not set. I guess you could flip the statements and put a >>>smp_mb between them. Probably not worth the trouble though. >>> >>No better to make it explicit, probably doesn't matter much in >>real-life. Thanks for the clarifications. >> > >Ah, it would be clearer as: > > if (arq->is_sync == REQ_SYNC) { > spin_lock(&aic->lock); > set_bit(AS_TASK_IORUNNING, &aic->state); > aic->last_end_request = jiffies; > spin_unlock(&aic->lock); > } > >Then it doesn't need comments :) >
Yeah thats was a bit silly of me I see why you got confused. I have actually fixed this up in mm3. So it should get through to Linus sometime after 2.6.0.
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