From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Wed, 5 Dec 2018 20:00:09 +0000 (-0500)
Subject: Teardown the notification thread after the sessiond clean-up
X-Git-Tag: v2.12.0-rc1~711
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=4a91420cefb94afc4a20042bdbe2564086dad3cb;p=lttng-tools.git

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 1fbfb1b05..d6bc01598 100644
--- 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 9809e6190..b42b282e1 100644
--- 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 525adcc6a..48b6bce3a 100644
--- 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 */