--- //depot/vendor/freebsd/src/sys/kern/kern_mutex.c	2010-05-11 18:31:25.000000000 0000
+++ //depot/projects/smpng/sys/kern/kern_mutex.c	2010-06-01 20:12:02.000000000 0000
@@ -348,6 +348,15 @@
 		return;
 	}
 
+	/*
+	 * If we have already panic'd and this is the thread that called
+	 * panic(), then don't block on any mutexes but silently succeed.
+	 * Otherwise, the kernel will deadlock since the scheduler isn't
+	 * going to run the thread that holds the lock we need.
+	 */
+	if (panicstr != NULL && curthread->td_flags & TDF_INPANIC)
+		return;
+
 	lock_profile_obtain_lock_failed(&m->lock_object,
 		    &contested, &waittime);
 	if (LOCK_LOG_TEST(&m->lock_object, opts))
@@ -664,6 +673,15 @@
 	}
 
 	/*
+	 * If we failed to unlock this lock and we are a thread that has
+	 * called panic(), it may be due to the bypass in _mtx_lock_sleep()
+	 * above.  In that case, just return and leave the lock alone to
+	 * avoid changing the state.
+	 */
+	if (panicstr != NULL && curthread->td_flags & TDF_INPANIC)
+		return;
+
+	/*
 	 * We have to lock the chain before the turnstile so this turnstile
 	 * can be removed from the hash list if it is empty.
 	 */