On 6/27/18 6:00 PM, Bart Van Assche wrote: > On 06/27/18 16:27, Ming Lei wrote: >> On Wed, Jun 27, 2018 at 01:02:12PM -0700, Bart Van Assche wrote: >>> Because the hctx lock is not held around the only >>> blk_mq_tag_wakeup_all() call in the block layer, the wait queue >>> entry removal in blk_mq_dispatch_wake() is protected by the wait >>> queue lock only. Since the hctx->dispatch_wait entry can occur on >>> any of the SBQ_WAIT_QUEUES, the wait queue presence check, adding >>> .dispatch_wait to a wait queue and removing the wait queue entry >>> must all be protected by both the hctx lock and the wait queue >>> lock. >> >> Actually we don't need to use hctx->lock for protecting >> hctx->dispatch_wait, and one new lock of hctx->dispatch_wait_lock is >> enough, please see the following patch: >> >> https://marc.info/?l=linux-block&m=152998658713265&w=2 >> >> Then we can avoid to disable irq when acquiring hctx->lock. > > I think it's more a matter of taste than a technical decision to choose > which patch goes upstream. I do think the split lock is cleaner in this case, since it avoids making hctx->lock irq disabling. -- Jens Axboe
