Teardown the notification thread after the sessiond clean-up

The notification thread may receive commands issued through the
call_rcu thread during the destruction of some of the sessiond's
data structure.

This change tears down the notification thread after the clean-up
has occured and the issuance of an RCU barrier. This ensures that
all previously-queued call_rcu work has been performed and that
any ensuing notification thread commands have been queued in return.

It is safe, at that point, to queue a "quit" command in the
notification thread's command queue. The notification thread's
shutdown method will issue the command and wait for its completion
before returning.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index 1fbfb1b0549383cd77e5334aad25338320cb6d56..d6bc015981d96246f3ef71dd98c0dea9bc3403b3 100644 (file)
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -1353,6 +1353,7 @@ int main(int argc, char **argv)
        /* Queue of rotation jobs populated by the sessiond-timer. */
        struct rotation_thread_timer_queue *rotation_timer_queue = NULL;
        struct lttng_thread *client_thread = NULL;
+       struct lttng_thread *notification_thread = NULL;
 
        init_kernel_workarounds();
 
@@ -1702,7 +1703,9 @@ int main(int argc, char **argv)
        }
 
        /* Create notification thread. */
-       if (!launch_notification_thread(notification_thread_handle)) {
+       notification_thread = launch_notification_thread(
+                       notification_thread_handle);
+       if (!notification_thread) {
                retval = -1;
                goto exit_notification;
        }
@@ -1837,6 +1840,11 @@ exit_init_data:
        rcu_thread_online();
        sessiond_cleanup();
 
+       if (notification_thread) {
+               lttng_thread_shutdown(notification_thread);
+               lttng_thread_put(notification_thread);
+       }
+
        /*
         * Ensure all prior call_rcu are done. call_rcu callbacks may push
         * hash tables to the ht_cleanup thread. Therefore, we ensure that

diff --git a/src/bin/lttng-sessiond/notification-thread.c b/src/bin/lttng-sessiond/notification-thread.c
index 9809e6190cd60cbb453cea62b704a62e6da84cc5..b42b282e10cfbc98e262eca77ad6fd6dbeac1213 100644 (file)
--- a/src/bin/lttng-sessiond/notification-thread.c
+++ b/src/bin/lttng-sessiond/notification-thread.c
@@ -653,7 +653,8 @@ bool shutdown_notification_thread(void *thread_data)
        return true;
 }
 
-bool launch_notification_thread(struct notification_thread_handle *handle)
+struct lttng_thread *launch_notification_thread(
+               struct notification_thread_handle *handle)
 {
        struct lttng_thread *thread;
 
@@ -672,8 +673,7 @@ bool launch_notification_thread(struct notification_thread_handle *handle)
         * (e.g. rotation thread).
         */
        wait_until_thread_is_ready(handle);
-       lttng_thread_put(thread);
-       return true;
+       return thread;
 error:
-       return false;
+       return NULL;
 }

diff --git a/src/bin/lttng-sessiond/notification-thread.h b/src/bin/lttng-sessiond/notification-thread.h
index 525adcc6a8124c6d97fdabc4c903bbb5c8371781..48b6bce3a49dcb10f2754877d7b3f8f98b67ab03 100644 (file)
--- a/src/bin/lttng-sessiond/notification-thread.h
+++ b/src/bin/lttng-sessiond/notification-thread.h
@@ -27,6 +27,7 @@
 #include <common/hashtable/hashtable.h>
 #include <pthread.h>
 #include <semaphore.h>
+#include "thread.h"
 
 struct notification_thread_handle {
        /*
@@ -216,6 +217,7 @@ struct notification_thread_handle *notification_thread_handle_create(
                struct lttng_pipe *kernel_channel_monitor_pipe);
 void notification_thread_handle_destroy(
                struct notification_thread_handle *handle);
-bool launch_notification_thread(struct notification_thread_handle *handle);
+struct lttng_thread *launch_notification_thread(
+               struct notification_thread_handle *handle);
 
 #endif /* NOTIFICATION_THREAD_H */