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From: Tasos Sahanidis <tasos@tasossah.com>
To: linux-block@vger.kernel.org
Cc: axboe@kernel.dk, efremov@linux.com, jkosina@suse.cz, tasos@tasossah.com
Subject: [PATCH] floppy: Fix hang in watchdog when disk is ejected
Date: Fri, 3 Sep 2021 09:47:58 +0300	[thread overview]
Message-ID: <399e486c-6540-db27-76aa-7a271b061f76@tasossah.com> (raw)

When the watchdog detects a disk change, it calls cancel_activity(),
which in turn tries to cancel the fd_timer delayed work.

In the above scenario, fd_timer_fn is set to fd_watchdog(), meaning
it is trying to cancel its own work.
This results in a hang as cancel_delayed_work_sync() is waiting for the
watchdog (itself) to return, which never happens.

This can be reproduced relatively consistently by attempting to read a
broken floppy, and ejecting it while IO is being attempted and retried.

To resolve this, this patch calls cancel_delayed_work() instead, which
cancels the work without waiting for the watchdog to return and finish.

Before this regression was introduced, the code in this section used
del_timer(), and not del_timer_sync() to delete the watchdog timer.

Fixes: 070ad7e793dc ("floppy: convert to delayed work and single-thread wq")
Signed-off-by: Tasos Sahanidis <tasos@tasossah.com>
---
 drivers/block/floppy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index fef79ea52..85464d72d 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -1014,7 +1014,7 @@ static DECLARE_DELAYED_WORK(fd_timer, fd_timer_workfn);
 static void cancel_activity(void)
 {
 	do_floppy = NULL;
-	cancel_delayed_work_sync(&fd_timer);
+	cancel_delayed_work(&fd_timer);
 	cancel_work_sync(&floppy_work);
 }
 
-- 
2.25.1


             reply	other threads:[~2021-09-03  6:50 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-03  6:47 Tasos Sahanidis [this message]
2021-09-18 22:33 ` Denis Efremov

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