linux-kernel - [PATCH 4.16 40/68] blk-mq: Directly schedule q->timeout

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Date:   Tue, 17 Apr 2018 17:57:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Sitsofe Wheeler <sitsofe@...il.com>,
        Meelis Roos <mroos@...ux.ee>, Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.16 40/68] blk-mq: Directly schedule q->timeout_work when aborting a request

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tejun Heo <tj@...nel.org>

commit bc6d65e6dc89c3b7ff78e4ad797117c122ffde8e upstream.

Request abortion is performed by overriding deadline to now and
scheduling timeout handling immediately.  For the latter part, the
code was using mod_timer(timeout, 0) which can't guarantee that the
timer runs afterwards.  Let's schedule the underlying work item
directly instead.

This fixes the hangs during probing reported by Sitsofe but it isn't
yet clear to me how the failure can happen reliably if it's just the
above described race condition.

Signed-off-by: Tejun Heo <tj@...nel.org>
Reported-by: Sitsofe Wheeler <sitsofe@...il.com>
Reported-by: Meelis Roos <mroos@...ux.ee>
Fixes: 358f70da49d7 ("blk-mq: make blk_abort_request() trigger timeout path")
Cc: stable@...r.kernel.org # v4.16
Link: http://lkml.kernel.org/r/CALjAwxh-PVYFnYFCJpGOja+m5SzZ8Sa4J7ohxdK=r8NyOF-EMA@mail.gmail.com
Link: http://lkml.kernel.org/r/alpine.LRH.2.21.1802261049140.4893@math.ut.ee
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-timeout.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -165,7 +165,7 @@ void blk_abort_request(struct request *r
 		 * No need for fancy synchronizations.
 		 */
 		blk_rq_set_deadline(req, jiffies);
-		mod_timer(&req->q->timeout, 0);
+		kblockd_schedule_work(&req->q->timeout_work);
 	} else {
 		if (blk_mark_rq_complete(req))
 			return;