proper waitpid() fix.

remove all waitpid() calls and use the event system to trap sigchld

(This used to be ctdb commit 77458b2b6b51b2970c12b0e5b097088d3fb9d358)

ctdb/server/ctdb_daemon.c

@@ -628,6 +628,27 @@ static int unlink_destructor(const char *name)
 	return 0;
 }
 
+static void sig_child_handler(struct event_context *ev,
+	struct signal_event *se, int signum, int count,
+	void *dont_care, 
+	void *private_data)
+{
+//	struct ctdb_context *ctdb = talloc_get_type(private_data, struct ctdb_context);
+	int status;
+	pid_t pid = -1;
+
+	while (pid != 0) {
+		pid = waitpid(-1, &status, WNOHANG);
+		if (pid == -1) {
+			DEBUG(DEBUG_ERR, (__location__ " waitpid() returned error. errno:%d\n", errno));
+			return;
+		}
+		if (pid > 0) {
+			DEBUG(DEBUG_DEBUG, ("SIGCHLD from %d\n", (int)pid));
+		}
+	}
+}
+
 /*
   start the protocol going as a daemon
 */
@@ -636,6 +657,7 @@ int ctdb_start_daemon(struct ctdb_context *ctdb, bool do_fork)
 	int res, ret = -1;
 	struct fd_event *fde;
 	const char *domain_socket_name;
+	struct signal_event *se;
 
 	/* get rid of any old sockets */
 	unlink(ctdb->daemon.name);
@@ -731,6 +753,16 @@ int ctdb_start_daemon(struct ctdb_context *ctdb, bool do_fork)
 	/* start the transport going */
 	ctdb_start_transport(ctdb);
 
+	/* set up a handler to pick up sigchld */
+	se = event_add_signal(ctdb->ev, ctdb,
+				     SIGCHLD, 0,
+				     sig_child_handler,
+				     ctdb);
+	if (se == NULL) {
+		DEBUG(DEBUG_CRIT,("Failed to set up signal handler for SIGCHLD\n"));
+		exit(1);
+	}
+	  
 	/* go into a wait loop to allow other nodes to complete */
 	event_loop_wait(ctdb->ev);
 

ctdb/server/ctdb_freeze.c

@@ -87,7 +87,6 @@ static int ctdb_freeze_handle_destructor(struct ctdb_freeze_handle *h)
 	ctdb->freeze_handle = NULL;
 
 	kill(h->child, SIGKILL);
-	waitpid(h->child, NULL, 0);
 	return 0;
 }
 

ctdb/server/ctdb_lockwait.c

@@ -72,7 +72,6 @@ static void lockwait_handler(struct event_context *ev, struct fd_event *fde,
 	tdb_chainlock_unmark(tdb, key);
 
 	kill(child, SIGKILL);
-	waitpid(child, NULL, 0);
 	talloc_free(tmp_ctx);
 }
 
@@ -80,7 +79,6 @@ static int lockwait_destructor(struct lockwait_handle *h)
 {
 	h->ctdb->statistics.pending_lockwait_calls--;
 	kill(h->child, SIGKILL);
-	waitpid(h->child, NULL, 0);
 	return 0;
 }
 

ctdb/server/ctdb_persistent.c

@@ -222,7 +222,6 @@ static int childwrite_destructor(struct childwrite_handle *h)
 {
 	h->ctdb->statistics.pending_childwrite_calls--;
 	kill(h->child, SIGKILL);
-	waitpid(h->child, NULL, 0);
 	return 0;
 }
 
@@ -260,7 +259,6 @@ static void childwrite_handler(struct event_context *ev, struct fd_event *fde,
 	callback(c, p);
 
 	kill(child, SIGKILL);
-	waitpid(child, NULL, 0);
 	talloc_free(tmp_ctx);
 }
 

ctdb/server/ctdb_recover.c

@@ -459,7 +459,6 @@ static void ctdb_set_recmode_timeout(struct event_context *ev, struct timed_even
 static int set_recmode_destructor(struct ctdb_set_recmode_state *state)
 {
 	kill(state->child, SIGKILL);
-	waitpid(state->child, NULL, 0);
 	return 0;
 }
 

ctdb/server/ctdb_recoverd.c

@@ -2933,11 +2933,6 @@ static void ctdb_check_recd(struct event_context *ev, struct timed_event *te,
 {
 	struct ctdb_context *ctdb = talloc_get_type(p, struct ctdb_context);
 
-	/* make sure we harvest the child if signals are blocked for some
-	   reason
-	*/
-	waitpid(ctdb->recoverd_pid, 0, WNOHANG);
-
 	if (kill(ctdb->recoverd_pid, 0) != 0) {
 		DEBUG(DEBUG_ERR,("Recovery daemon (pid:%d) is no longer running. Shutting down main daemon\n", (int)ctdb->recoverd_pid));
 
@@ -2958,6 +2953,27 @@ static void ctdb_check_recd(struct event_context *ev, struct timed_event *te,
 			ctdb_check_recd, ctdb);
 }
 
+static void recd_sig_child_handler(struct event_context *ev,
+	struct signal_event *se, int signum, int count,
+	void *dont_care, 
+	void *private_data)
+{
+//	struct ctdb_context *ctdb = talloc_get_type(private_data, struct ctdb_context);
+	int status;
+	pid_t pid = -1;
+
+	while (pid != 0) {
+		pid = waitpid(-1, &status, WNOHANG);
+		if (pid == -1) {
+			DEBUG(DEBUG_ERR, (__location__ " waitpid() returned error. errno:%d\n", errno));
+			return;
+		}
+		if (pid > 0) {
+			DEBUG(DEBUG_DEBUG, ("RECD SIGCHLD from %d\n", (int)pid));
+		}
+	}
+}
+
 /*
   startup the recovery daemon as a child of the main ctdb daemon
  */
@@ -2965,6 +2981,7 @@ int ctdb_start_recoverd(struct ctdb_context *ctdb)
 {
 	int ret;
 	int fd[2];
+	struct signal_event *se;
 
 	if (pipe(fd) != 0) {
 		return -1;
@@ -3016,6 +3033,16 @@ int ctdb_start_recoverd(struct ctdb_context *ctdb)
 		exit(1);
 	}
 
+	/* set up a handler to pick up sigchld */
+	se = event_add_signal(ctdb->ev, ctdb,
+				     SIGCHLD, 0,
+				     recd_sig_child_handler,
+				     ctdb);
+	if (se == NULL) {
+		DEBUG(DEBUG_CRIT,("Failed to set up signal handler for SIGCHLD in recovery daemon\n"));
+		exit(1);
+	}
+
 	monitor_cluster(ctdb);
 
 	DEBUG(DEBUG_ALERT,("ERROR: ctdb_recoverd finished!?\n"));

ctdb/server/ctdb_traverse.c

@@ -74,7 +74,6 @@ static void ctdb_traverse_local_handler(uint8_t *rawdata, size_t length, void *p
 static int traverse_local_destructor(struct ctdb_traverse_local_handle *h)
 {
 	kill(h->child, SIGKILL);
-	waitpid(h->child, NULL, 0);
 	return 0;
 }
 

ctdb/server/eventscript.c

@@ -210,18 +210,16 @@ static void ctdb_event_script_handler(struct event_context *ev, struct fd_event
 {
 	struct ctdb_event_script_state *state = 
 		talloc_get_type(p, struct ctdb_event_script_state);
-	int status = -1;
 	void (*callback)(struct ctdb_context *, int, void *) = state->callback;
 	void *private_data = state->private_data;
 	struct ctdb_context *ctdb = state->ctdb;
+	signed char rt = -1;
+
+	read(state->fd[0], &rt, sizeof(rt));
 
-	waitpid(state->child, &status, 0);
-	if (status != -1) {
-		status = WEXITSTATUS(status);
-	}
 	talloc_set_destructor(state, NULL);
 	talloc_free(state);
-	callback(ctdb, status, private_data);
+	callback(ctdb, rt, private_data);
 
 	ctdb->event_script_timeouts = 0;
 }
@@ -293,7 +291,6 @@ static int event_script_destructor(struct ctdb_event_script_state *state)
 {
 	DEBUG(DEBUG_ERR,(__location__ " Sending SIGTERM to child pid:%d\n", state->child));
 	kill(state->child, SIGTERM);
-	waitpid(state->child, NULL, 0);
 	return 0;
 }
 
@@ -336,13 +333,18 @@ static int ctdb_event_script_callback_v(struct ctdb_context *ctdb,
 	}
 
 	if (state->child == 0) {
+		signed char rt;
+
 		close(state->fd[0]);
 		if (ctdb->do_setsched) {
 			ctdb_restore_scheduler(ctdb);
 		}
 		set_close_on_exec(state->fd[1]);
-		ret = ctdb_event_script_v(ctdb, state->options);
+		rt = ctdb_event_script_v(ctdb, state->options);
-		_exit(ret);
+		while ((ret = write(state->fd[1], &rt, sizeof(rt))) != sizeof(rt)) {
+			sleep(1);
+		}
+		_exit(rt);
 	}
 
 	talloc_set_destructor(state, event_script_destructor);