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.[1]
[1] 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.
Cc: stable@vger.kernel.org Signed-off-by: Alan Jenkins alan.christopher.jenkins@gmail.com --- block/blk-core.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c index abcb8684ba67..5a6d20069364 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -915,7 +915,6 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
while (true) { bool success = false; - int ret;
rcu_read_lock(); if (percpu_ref_tryget_live(&q->q_usage_counter)) { @@ -947,14 +946,12 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) */ smp_rmb();
- ret = wait_event_interruptible(q->mq_freeze_wq, + wait_event(q->mq_freeze_wq, (atomic_read(&q->mq_freeze_depth) == 0 && (preempt || !blk_queue_preempt_only(q))) || blk_queue_dying(q)); if (blk_queue_dying(q)) return -ENODEV; - if (ret) - return ret; } }