From: Alan Jenkins <alan.christopher.jenkins@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org
Cc: Bart Van Assche <Bart.VanAssche@wdc.com>,
linux-kernel@vger.kernel.org,
Alan Jenkins <alan.christopher.jenkins@gmail.com>,
stable@vger.kernel.org
Subject: [PATCH v2] block: do not use interruptible wait anywhere
Date: Thu, 12 Apr 2018 19:11:58 +0100 [thread overview]
Message-ID: <20180412181158.8884-1-alan.christopher.jenkins@gmail.com> (raw)
In-Reply-To: <13e67e1243ebd96f3f56a150d47444ada47ebde0.camel@wdc.com>
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>
---
v2: fix indentation
block/blk-core.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index abcb8684ba67..1a762f3980f2 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,
- (atomic_read(&q->mq_freeze_depth) == 0 &&
- (preempt || !blk_queue_preempt_only(q))) ||
- blk_queue_dying(q));
+ 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;
}
}
--
2.14.3
next prev parent reply other threads:[~2018-04-12 18:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-12 16:23 [PATCH] block: do not use interruptible wait anywhere Alan Jenkins
2018-04-12 17:51 ` Bart Van Assche
2018-04-12 18:11 ` Alan Jenkins [this message]
2018-04-13 8:31 ` [PATCH v2] " Johannes Thumshirn
2018-04-14 19:46 ` blktest for " Alan Jenkins
2018-04-14 19:52 ` Jens Axboe
2018-04-15 12:15 ` Alan Jenkins
2018-04-14 19:54 ` Jens Axboe
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