Fix: perform statedump before replying to sessiond

If a stop command immediately follows a start command, the consumer
daemon will stop event recording in the ring buffers shared memory
control structures before the sessiond sends further commands to the
application. Therefore, a stop-after-start may be performed concurrently
with the statedump, leading to have parts of the statedump being
missing. This case may always happen if an application exits during
statedump, but it is not expected to have incomplete statedump in the
stop-after-start use case.

The session daemon statedump regeneration tests expect that the
statedump is completed when the regeneration command returns. This also
requires that we perform the statedump in lttng-ust before replying to
the session daemon command.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 4a21866358b66a4d9f766abdfd47665e2cffe13d..7cd6a227d66c3bede0f7e244a02038c2c8de668b 100644 (file)
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -956,6 +956,21 @@ int handle_message(struct sock_info *sock_info,
                }
        }
        DBG("Return value: %d", lur.ret_val);
+
+       ust_unlock();
+
+       /*
+        * Performed delayed statedump operations outside of the UST
+        * lock. We need to take the dynamic loader lock before we take
+        * the UST lock internally within handle_pending_statedump().
+         */
+       handle_pending_statedump(sock_info);
+
+       if (ust_lock()) {
+               ret = -LTTNG_UST_ERR_EXITING;
+               goto error;
+       }
+
        ret = send_reply(sock, &lur);
        if (ret < 0) {
                DBG("error sending reply");
@@ -986,13 +1001,6 @@ int handle_message(struct sock_info *sock_info,
 error:
        ust_unlock();
 
-       /*
-        * Performed delayed statedump operations outside of the UST
-        * lock. We need to take the dynamic loader lock before we take
-        * the UST lock internally within handle_pending_statedump().
-         */
-       handle_pending_statedump(sock_info);
-
        return ret;
 }