On Sat, 2018-01-27 at 19:23 -0500, Mike Snitzer wrote: > On Sat, Jan 27 2018 at 5:12pm -0500, > Bart Van Assche <Bart.VanAssche@xxxxxxx> wrote: > > - The patch at the start of this thread introduces a regression in the > > SCSI core, namely a queue stall if a request completion occurs concurrently > > with the newly added BLK_MQ_S_SCHED_RESTART test in the blk-mq core. > > And why is this supposed race unique to SCSI core? That race is not unique to the SCSI core. It is possible that the patch at the start of this thread introduces the same race in other block drivers but I have not yet tried to verify that. > Fact is Ming dutifully implemented what Jens suggested. That's a misleading statement. Jens proposed to introduce a new status code (which he called "NO_DEV_RESOURCE") but did not specify any of the other aspects of Ming's patch. Jens definitely did not ask to introduce new race conditions. See also https://www.spinics.net/lists/kernel/msg2703154.html Bart.