X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Flib%2Flttng-ctl%2Fchannel.c;h=5271aa13fbd76218fca47b8984c6a055fc84b35f;hb=3b33e9e731f2091e8aa13ea035c295ed6f101eac;hp=49a3684dbb1cbad3c6fb11ae5818238fdf806f0a;hpb=3647288fe42b25340f905046f3bd9aef21e12aaa;p=lttng-tools.git

diff --git a/src/lib/lttng-ctl/channel.c b/src/lib/lttng-ctl/channel.c
index 49a3684db..5271aa13f 100644
--- a/src/lib/lttng-ctl/channel.c
+++ b/src/lib/lttng-ctl/channel.c
@@ -211,6 +211,7 @@ lttng_notification_channel_get_next_notification(
 	struct lttng_notification *notification = NULL;
 	enum lttng_notification_channel_status status =
 			LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
+	fd_set read_fds;
 
 	if (!channel || !_notification) {
 		status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
@@ -239,6 +240,28 @@ lttng_notification_channel_get_next_notification(
 		goto end_unlock;
 	}
 
+	/*
+	 * Block on select() instead of the message reception itself as the
+	 * recvmsg() wrappers always restard on EINTR. We choose to wait
+	 * using select() in order to:
+	 *   1) Return if a signal occurs,
+	 *   2) Not deal with partially received messages.
+	 *
+	 * The drawback to this approach is that we assume that messages
+	 * are complete/well formed. If a message is shorter than its
+	 * announced length, receive_message() will block on recvmsg()
+	 * and never return (even if a signal is received).
+	 */
+	FD_ZERO(&read_fds);
+	FD_SET(channel->socket, &read_fds);
+	ret = select(channel->socket + 1, &read_fds, NULL, NULL, NULL);
+	if (ret == -1) {
+		status = errno == EINTR ?
+			LTTNG_NOTIFICATION_CHANNEL_STATUS_INTERRUPTED :
+			LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
+		goto end_unlock;
+	}
+
 	ret = receive_message(channel);
 	if (ret) {
 		status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
@@ -266,10 +289,8 @@ lttng_notification_channel_get_next_notification(
 
 end_unlock:
 	pthread_mutex_unlock(&channel->lock);
+	*_notification = notification;
 end:
-	if (_notification) {
-		*_notification = notification;
-	}
 	return status;
 }
 
@@ -430,14 +451,14 @@ lttng_notification_channel_has_pending_notification(
 	case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION:
 		ret = enqueue_notification_from_current_message(channel);
 		if (ret) {
-			goto end;
+			goto end_unlock;
 		}
 		*_notification_pending = true;
 		break;
 	case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED:
 		ret = enqueue_dropped_notification(channel);
 		if (ret) {
-			goto end;
+			goto end_unlock;
 		}
 		*_notification_pending = true;
 		break;