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Commit ac4c4fc8 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Martin Schwidefsky
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s390/cmm: avoid add_timer on concurrently used timer 



cmm_set_timer could be called concurrently from cmm_thread, cmm proc
handler, upon cmm smsg receive and timer function itself. To avoid
potential race condition and hitting BUG_ON in add_timer on already
pending timer simply reuse mod_timer which is according to
documentation "the only safe way to modify the timeout" with multiple
unserialized concurrent users. mod_timer can handle both active and
inactive timers which allows to carry out minor code simplification as
well.

Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent a09baa95

arch/s390/mm/cmm.c

+1 −6
Original line number Diff line number Diff line
@@ -191,12 +191,7 @@ static void cmm_set_timer(void) 
			del_timer(&cmm_timer);

		return;

	}

	if (timer_pending(&cmm_timer)) {

		if (mod_timer(&cmm_timer, jiffies + cmm_timeout_seconds*HZ))

			return;

	}

	cmm_timer.expires = jiffies + cmm_timeout_seconds*HZ;

	add_timer(&cmm_timer);

	mod_timer(&cmm_timer, jiffies + cmm_timeout_seconds * HZ);

}



static void cmm_timer_fn(struct timer_list *unused)