Fix: Consumerd error socket connect race

Fixes #366

Signed-off-by: David Goulet <dgoulet@efficios.com>

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index 736ec83ff8712d891f92d3a2724f7085672b924f..022bbc6d1dc5b293974166f0a92bd04818ba29e2 100644 (file)
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -857,13 +857,6 @@ static void *thread_manage_consumer(void *data)
         */
        health_poll_update(&consumer_data->health);
 
-       health_code_update(&consumer_data->health);
-
-       ret = lttcomm_listen_unix_sock(consumer_data->err_sock);
-       if (ret < 0) {
-               goto error_listen;
-       }
-
        /*
         * Pass 2 as size here for the thread quit pipe and kconsumerd_err_sock.
         * Nothing more will be added to this poll set.
@@ -873,6 +866,11 @@ static void *thread_manage_consumer(void *data)
                goto error_poll;
        }
 
+       /*
+        * The error socket here is already in a listening state which was done
+        * just before spawning this thread to avoid a race between the consumer
+        * daemon exec trying to connect and the listen() call.
+        */
        ret = lttng_poll_add(&events, consumer_data->err_sock, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
@@ -1068,7 +1066,6 @@ error:
 
        lttng_poll_clean(&events);
 error_poll:
-error_listen:
        if (err) {
                health_error(&consumer_data->health);
                ERR("Health error occurred in %s", __func__);
@@ -1826,7 +1823,17 @@ error:
  */
 static int start_consumerd(struct consumer_data *consumer_data)
 {
-       int ret;
+       int ret, err;
+
+       /*
+        * Set the listen() state on the socket since there is a possible race
+        * between the exec() of the consumer daemon and this call if place in the
+        * consumer thread. See bug #366 for more details.
+        */
+       ret = lttcomm_listen_unix_sock(consumer_data->err_sock);
+       if (ret < 0) {
+               goto error;
+       }
 
        pthread_mutex_lock(&consumer_data->pid_mutex);
        if (consumer_data->pid != 0) {
@@ -1857,6 +1864,13 @@ end:
        return 0;
 
 error:
+       /* Cleanup already created socket on error. */
+       if (consumer_data->err_sock >= 0) {
+               err = close(consumer_data->err_sock);
+               if (err < 0) {
+                       PERROR("close consumer data error socket");
+               }
+       }
        return ret;
 }