From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Sat, 25 Jul 2015 20:24:05 +0000 (-0400)
Subject: Fix: RCU read-side lock released too early in destroy_agent_app
X-Git-Tag: v2.6.1~86
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=022541e7a5ccb09a92e469d87d8e5fe9fc9d7512;p=lttng-tools.git

Fix: RCU read-side lock released too early in destroy_agent_app

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

diff --git a/src/bin/lttng-sessiond/agent-thread.c b/src/bin/lttng-sessiond/agent-thread.c
index 4c1457fe0..dbbdfde4a 100644
--- a/src/bin/lttng-sessiond/agent-thread.c
+++ b/src/bin/lttng-sessiond/agent-thread.c
@@ -89,13 +89,13 @@ static void destroy_agent_app(int sock)
 	rcu_read_lock();
 	app = agent_find_app_by_sock(sock);
 	assert(app);
-	rcu_read_unlock();
 
-	/* RCU read side lock is taken in this function call. */
+	/* RCU read side lock is assumed to be held by this function. */
 	agent_delete_app(app);
 
 	/* The application is freed in a RCU call but the socket is closed here. */
 	agent_destroy_app(app);
+	rcu_read_unlock();
 }
 
 /*
diff --git a/src/bin/lttng-sessiond/agent.c b/src/bin/lttng-sessiond/agent.c
index 8992d2d80..1bf490f5a 100644
--- a/src/bin/lttng-sessiond/agent.c
+++ b/src/bin/lttng-sessiond/agent.c
@@ -677,6 +677,8 @@ void agent_add_app(struct agent_app *app)
 
 /*
  * Delete agent application from the global hash table.
+ *
+ * rcu_read_lock() must be held by the caller.
  */
 void agent_delete_app(struct agent_app *app)
 {
@@ -688,9 +690,7 @@ void agent_delete_app(struct agent_app *app)
 	DBG3("Agent deleting app pid: %d and sock: %d", app->pid, app->sock->fd);
 
 	iter.iter.node = &app->node.node;
-	rcu_read_lock();
 	ret = lttng_ht_del(agent_apps_ht_by_sock, &iter);
-	rcu_read_unlock();
 	assert(!ret);
 }