Messages in this thread | | | Date | Fri, 16 May 2014 23:43:17 +0800 | Subject | Re: [PATCH v1] virtio_blk: fix race between start and stop queue | From | Ming Lei <> |
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On Fri, May 16, 2014 at 11:32 PM, Jens Axboe <axboe@kernel.dk> wrote: > On 2014-05-16 09:31, Ming Lei wrote: >> >> When there isn't enough vring descriptor for adding to vq, >> blk-mq will be put as stopped state until some of pending >> descriptors are completed & freed. >> >> Unfortunately, the vq's interrupt may come just before >> blk-mq's BLK_MQ_S_STOPPED flag is set, so the blk-mq will >> still be kept as stopped even though lots of descriptors >> are completed and freed in the interrupt handler. The worst >> case is that all pending descriptors are freed in the >> interrupt handler, and the queue is kept as stopped forever. >> >> This patch fixes the problem by starting/stopping blk-mq >> with holding vq_lock. > > > Thanks, this looks good, I'll apply it for 3.16 (with a stable marker, even > if it is an unlikely event).
Thanks.
It shouldn't be very difficult to happen in case of non-indirect descriptor, and it is easy to reproduce when module parameter of 'virtblk_queue_depth' is bigger than vq->num_free for non-indirect case.
Thanks, -- Ming Lei
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