| From 1dc3039bc87ae7d19a990c3ee71cfd8a9068f428 Mon Sep 17 00:00:00 2001 |
| From: Alan Jenkins <alan.christopher.jenkins@gmail.com> |
| Date: Thu, 12 Apr 2018 19:11:58 +0100 |
| Subject: block: do not use interruptible wait anywhere |
| |
| From: Alan Jenkins <alan.christopher.jenkins@gmail.com> |
| |
| commit 1dc3039bc87ae7d19a990c3ee71cfd8a9068f428 upstream. |
| |
| 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. |
| |
| Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Alan Jenkins <alan.christopher.jenkins@gmail.com> |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| block/blk-core.c | 9 +++------ |
| 1 file changed, 3 insertions(+), 6 deletions(-) |
| |
| --- a/block/blk-core.c |
| +++ b/block/blk-core.c |
| @@ -652,7 +652,6 @@ EXPORT_SYMBOL(blk_alloc_queue); |
| int blk_queue_enter(struct request_queue *q, bool nowait) |
| { |
| while (true) { |
| - int ret; |
| |
| if (percpu_ref_tryget_live(&q->q_usage_counter)) |
| return 0; |
| @@ -660,13 +659,11 @@ int blk_queue_enter(struct request_queue |
| if (nowait) |
| return -EBUSY; |
| |
| - ret = wait_event_interruptible(q->mq_freeze_wq, |
| - !atomic_read(&q->mq_freeze_depth) || |
| - blk_queue_dying(q)); |
| + wait_event(q->mq_freeze_wq, |
| + !atomic_read(&q->mq_freeze_depth) || |
| + blk_queue_dying(q)); |
| if (blk_queue_dying(q)) |
| return -ENODEV; |
| - if (ret) |
| - return ret; |
| } |
| } |
| |