From ac4c4fc87d6beb6dd8287f24670e5e81c24b1de7 Mon Sep 17 00:00:00 2001 From: Vasily Gorbik Date: Fri, 13 Jul 2018 08:13:13 +0200 Subject: [PATCH] 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: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Martin Schwidefsky --- arch/s390/mm/cmm.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c index 50d8d1c887a4..510a18299196 100644 --- a/arch/s390/mm/cmm.c +++ b/arch/s390/mm/cmm.c @@ -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)