Messages in this thread | | | Date | Thu, 13 Nov 2003 12:01:43 +0100 | From | Jens Axboe <> | Subject | Re: AS spin lock bugs |
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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.
-- Jens Axboe
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