On Sat, 2017-12-02 at 08:36 +0800, Ming Lei wrote: > On Fri, Dec 01, 2017 at 07:52:14PM +0000, Bart Van Assche wrote: > > On Fri, 2017-12-01 at 10:58 +0800, Ming Lei wrote: > > > On Thu, Nov 30, 2017 at 04:08:45PM -0800, Bart Van Assche wrote: > > > > blk_mq_dispatch_rq_list() is called. Make sure that > > > > BLK_MQ_S_SCHED_RESTART is set before any blk_mq_dispatch_rq_list() > > > > call occurs. > > > > > > > > Fixes: commit b347689ffbca ("blk-mq-sched: improve dispatching from sw queue") > > > > > > We always mark RESTART state bit just before dispatching from ->dispatch_list, > > > this way has been there before b347689ffbca, which doesn't change this > > > RESTART mechanism, so please explain a bit why it is a fix on commit > > > b347689ffbca. > > > > I'm not completely sure which patch introduced the lockup fixed by this patch > > but I will have another look whether this was really introduced by commit > > b347689ffbca. > > Please make sure 'Fixes' tag correct. Further tests have shown that the lockup I referred to does not occur before commit b347689ffbca but that it occurs with b347689ffbca. I think that shows clearly that commit b347689ffbca introduced this lockup. Bart.