From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Wed, 23 Jan 2019 20:29:14 +0000 (-0500)
Subject: Fix: missing rcu read locking in trigger "unregister all" command
X-Git-Tag: v2.12.0-rc1~663
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=763de384811082b26bafbce1c65d38032ef6ed30;p=lttng-tools.git

Fix: missing rcu read locking in trigger "unregister all" command

While the notification subsystem all runs within a single thread,
the iteration over the triggers hash table must be protected using
the RCU read-side lock since the RCU worker may resize the hash
table while the iteration is performed.

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

diff --git a/src/bin/lttng-sessiond/notification-thread-events.c b/src/bin/lttng-sessiond/notification-thread-events.c
index 9d82b8313..052689a0e 100644
--- a/src/bin/lttng-sessiond/notification-thread-events.c
+++ b/src/bin/lttng-sessiond/notification-thread-events.c
@@ -2544,6 +2544,7 @@ int handle_notification_thread_trigger_unregister_all(
 	struct cds_lfht_iter iter;
 	struct lttng_trigger_ht_element *trigger_ht_element;
 
+	rcu_read_lock();
 	cds_lfht_for_each_entry(state->triggers_ht, &iter, trigger_ht_element,
 			node) {
 		int ret = handle_notification_thread_command_unregister_trigger(
@@ -2552,6 +2553,7 @@ int handle_notification_thread_trigger_unregister_all(
 			error_occurred = true;
 		}
 	}
+	rcu_read_unlock();
 	return error_occurred ? -1 : 0;
 }