Allow get_next_notification to return when interrupted

[lttng-tools.git] / src / lib / lttng-ctl / channel.c

diff --git a/src/lib/lttng-ctl/channel.c b/src/lib/lttng-ctl/channel.c
index 5214fe73a41eeae6d96985e16fece47d45f1d7f8..5487d051b5013fd60b080491ce865966bc6ffeab 100644 (file)
--- 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;