diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c
--- a/sys/kern/kern_mutex.c
+++ b/sys/kern/kern_mutex.c
@@ -915,7 +915,13 @@
 					break;
 				continue;
 			}
-			MPASS(v != tid);
+			/* if two timers lock, v and tid both are clock tid,
+			 * so they are equal */
+			if (v == tid) {
+				m->mtx_recurse++;
+				MPASS(m == td->td_lock);
+				break;
+			}
 			lock_profile_obtain_lock_failed(&m->lock_object, true,
 			    &contested, &waittime);
 			/* Give interrupts a chance while we spin. */