document metadata_switch_timer() locking constraints

Reviewed-by: Julien Desfossez <julien.desfossez@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/src/common/consumer-timer.c b/src/common/consumer-timer.c
index f9c41c0eb0f8f9f32def26028f743ce7df45d322..f2dff4cd980aae5258cfc19a3c268bd800c955c8 100644 (file)
--- a/src/common/consumer-timer.c
+++ b/src/common/consumer-timer.c
@@ -56,6 +56,10 @@ static void setmask(sigset_t *mask)
 
 /*
  * Execute action on a timer switch.
+ *
+ * Beware: metadata_switch_timer() should *never* take a mutex also held
+ * while consumer_timer_switch_stop() is called. It would result in
+ * deadlocks.
  */
 static void metadata_switch_timer(struct lttng_consumer_local_data *ctx,
                int sig, siginfo_t *si, void *uc)