Fix witness/fork() interactions.

Fix witness to clear its list of owned mutexes in the child if
platform-specific malloc_mutex code re-initializes mutexes rather than
unlocking them.

include/jemalloc/internal/private_symbols.txt

@@ -594,7 +594,8 @@ witness_lock_error
 witness_lockless_error
 witness_not_owner_error
 witness_owner_error
-witness_postfork
+witness_postfork_child
+witness_postfork_parent
 witness_prefork
 witness_unlock
 witnesses_cleanup

include/jemalloc/internal/witness.h

@@ -96,7 +96,8 @@ void	witness_assert_lockless(tsd_t *tsd);
 void	witnesses_cleanup(tsd_t *tsd);
 void	witness_fork_cleanup(tsd_t *tsd);
 void	witness_prefork(tsd_t *tsd);
-void	witness_postfork(tsd_t *tsd);
+void	witness_postfork_parent(tsd_t *tsd);
+void	witness_postfork_child(tsd_t *tsd);
 
 #endif /* JEMALLOC_H_EXTERNS */
 /******************************************************************************/

src/jemalloc.c

@@ -2770,8 +2770,8 @@ _malloc_prefork(void)
 
 	narenas = narenas_total_get();
 
-	/* Acquire all mutexes in a safe order. */
 	witness_prefork(tsd);
+	/* Acquire all mutexes in a safe order. */
 	ctl_prefork(tsd);
 	malloc_mutex_prefork(tsd, &arenas_lock);
 	prof_prefork0(tsd);
@@ -2815,6 +2815,7 @@ _malloc_postfork(void)
 
 	tsd = tsd_fetch();
 
+	witness_postfork_parent(tsd);
 	/* Release all mutexes, now that fork() has completed. */
 	chunk_postfork_parent(tsd);
 	base_postfork_parent(tsd);
@@ -2827,7 +2828,6 @@ _malloc_postfork(void)
 	prof_postfork_parent(tsd);
 	malloc_mutex_postfork_parent(tsd, &arenas_lock);
 	ctl_postfork_parent(tsd);
-	witness_postfork(tsd);
 }
 
 void
@@ -2840,6 +2840,7 @@ jemalloc_postfork_child(void)
 
 	tsd = tsd_fetch();
 
+	witness_postfork_child(tsd);
 	/* Release all mutexes, now that fork() has completed. */
 	chunk_postfork_child(tsd);
 	base_postfork_child(tsd);
@@ -2852,7 +2853,6 @@ jemalloc_postfork_child(void)
 	prof_postfork_child(tsd);
 	malloc_mutex_postfork_child(tsd, &arenas_lock);
 	ctl_postfork_child(tsd);
-	witness_postfork(tsd);
 }
 
 /******************************************************************************/

src/witness.c

@@ -222,8 +222,20 @@ witness_prefork(tsd_t *tsd)
 }
 
 void
-witness_postfork(tsd_t *tsd)
+witness_postfork_parent(tsd_t *tsd)
 {
 
 	tsd_witness_fork_set(tsd, false);
 }
+
+void
+witness_postfork_child(tsd_t *tsd)
+{
+#ifndef JEMALLOC_MUTEX_INIT_CB
+	witness_list_t *witnesses;
+
+	witnesses = tsd_witnessesp_get(tsd);
+	ql_new(witnesses);
+#endif
+	tsd_witness_fork_set(tsd, false);
+}

test/unit/fork.c

@@ -11,6 +11,13 @@ TEST_BEGIN(test_fork)
 	assert_ptr_not_null(p, "Unexpected malloc() failure");
 
 	pid = fork();
+
+	free(p);
+
+	p = malloc(64);
+	assert_ptr_not_null(p, "Unexpected malloc() failure");
+	free(p);
+
 	if (pid == -1) {
 		/* Error. */
 		test_fail("Unexpected fork() failure");
@@ -21,11 +28,23 @@ TEST_BEGIN(test_fork)
 		int status;
 
 		/* Parent. */
-		free(p);
+		while (true) {
-		do {
 			if (waitpid(pid, &status, 0) == -1)
 				test_fail("Unexpected waitpid() failure");
-		} while (!WIFEXITED(status) && !WIFSIGNALED(status));
+			if (WIFSIGNALED(status)) {
+				test_fail("Unexpected child termination due to "
+				    "signal %d", WTERMSIG(status));
+				break;
+			}
+			if (WIFEXITED(status)) {
+				if (WEXITSTATUS(status) != 0) {
+					test_fail(
+					    "Unexpected child exit value %d",
+					    WEXITSTATUS(status));
+				}
+				break;
+			}
+		}
 	}
 }
 TEST_END