Messages in this thread | | | Date | Mon, 5 Apr 2010 18:13:13 +0800 | From | Herbert Xu <> | Subject | Re: [PATCH ide#master] ide: clean up timed out request handling |
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On Mon, Apr 05, 2010 at 06:17:43PM +0900, Tejun Heo wrote: > 8f6205cd572fece673da0255d74843680f67f879 introduced a bug where a > timed out DMA request is never requeued and lost. > 6072f7491f5ef391a575e18a1165e72a3eef1601 fixed this by making > ide_dma_timeout_retry() requeue the request itself. While the fix is > correct, it makes DMA and non-DMA paths asymmetric regarding how the > in flight request is requeued. > > As long as hwif->rq is set, the IDE driver is assuming ownership of > the request and the request should either be completed or requeued > when clearing hwif->rq. In the timeout path, the ide driver holds > onto the request as long as the recovery action (ie. reset) is in > progress and clears it after the state machine is stopped (ide_stopped > return), so the existing requeueing logic is correct. The bug > occurred because ide_dma_timeout_retry() explicitly clears hwif->rq > without requeueing it. > > ide_dma_timeout_retry() is called only by ide_timer_expiry() and > returns ide_started only when ide_error() would return it - ie. after > reset state machine has started in which case the state machine will > eventually end up executing the ide_stopped path in ide_timer_expiry() > after reset protocol is complete. So, there is no need to clear > hwif->rq from ide_dma_timeout_retry(). ide_timer_expiry() will handle > it the same way as PIO timeout path. > > Kill hwif->rq clearing and requeueing from ide_dma_timeout_retry() and > let ide_timer_expiry() deal with it. The end result should remain the > same. > > grepping shows ide_dma_timeout_retry() is the only site which clears > hwif->rq without taking care of the request, so there shouldn't be > similar fallouts. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Cc: Herbert Xu <herbert@gondor.apana.org.au> > Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> > --- > Herbert, can you please test this survives your test case?
I'll put it on my test machine.
However, as this bug triggers rarely (it's a race condition between qemu and ide), I don't expect a negative result any time soon.
In any case, your patch looks good to me.
Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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