[dm-devel] [PATCH 2/2] multipathd: Avoid that a deadlock is triggered sporadically during shutdown

[Bart Van Assche]

pthread_cond_wait() is a thread cancellation point. If a thread that
is waiting in pthread_cond_wait() is canceled it is possible that the
mutex is re-acquired before the first cancellation cleanup handler
is called. In this case the cleanup handler is uevq_stop() and that
function locks uevq_lock. Avoid that calling uevq_stop() results in
a deadlock due to an attempt to lock a non-recursive mutex recursively.

Signed-off-by: Bart Van Assche <bart.vanassche at sandisk.com>
---
 libmultipath/uevent.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
index 6247898..85fd2fb 100644
--- a/libmultipath/uevent.c
+++ b/libmultipath/uevent.c
@@ -52,7 +52,7 @@ typedef int (uev_trigger)(struct uevent *, void * trigger_data);
 
 pthread_t uevq_thr;
 LIST_HEAD(uevq);
-pthread_mutex_t uevq_lock = PTHREAD_MUTEX_INITIALIZER;
+pthread_mutex_t uevq_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
 pthread_mutex_t *uevq_lockp = &uevq_lock;
 pthread_cond_t uev_cond = PTHREAD_COND_INITIALIZER;
 pthread_cond_t *uev_condp = &uev_cond;
-- 
2.10.0