On 4/12/18 12:11 PM, Alan Jenkins wrote: > When blk_queue_enter() waits for a queue to unfreeze, or unset the > PREEMPT_ONLY flag, do not allow it to be interrupted by a signal. > > The PREEMPT_ONLY flag was introduced later in commit 3a0a529971ec > ("block, scsi: Make SCSI quiesce and resume work reliably"). Note the SCSI > device is resumed asynchronously, i.e. after un-freezing userspace tasks. > > So that commit exposed the bug as a regression in v4.15. A mysterious > SIGBUS (or -EIO) sometimes happened during the time the device was being > resumed. Most frequently, there was no kernel log message, and we saw Xorg > or Xwayland killed by SIGBUS. > >  E.g. https://bugzilla.redhat.com/show_bug.cgi?id=1553979 > > Without this fix, I get an IO error in this test: > > # dd if=/dev/sda of=/dev/null iflag=direct & \ > while killall -SIGUSR1 dd; do sleep 0.1; done & \ > echo mem > /sys/power/state ; \ > sleep 5; killall dd # stop after 5 seconds > > The interruptible wait was added to blk_queue_enter in > commit 3ef28e83ab15 ("block: generic request_queue reference counting"). > Before then, the interruptible wait was only in blk-mq, but I don't think > it could ever have been correct.
Applied, thanks. Still want that test in blktests, though! -- Jens Axboe