From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Thu, 13 Nov 2014 21:23:04 +0000 (-0500)
Subject: Fix: missing rcu_read_lock when calling trace_ust_find_agent()
X-Git-Tag: v2.6.0-rc4~61
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=43ee60cefa1fb0ddd2ef4b616c0debfd977c56ec;p=lttng-tools.git

Fix: missing rcu_read_lock when calling trace_ust_find_agent()

Added a comment to note that this function is assumed to be
called with the rcu_read_lock held.

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 0e827a445..56613a54f 100644
--- a/src/bin/lttng-sessiond/agent-thread.c
+++ b/src/bin/lttng-sessiond/agent-thread.c
@@ -60,10 +60,12 @@ static void update_agent_app(struct agent_app *app)
 		if (session->ust_session) {
 			struct agent *agt;
 
+			rcu_read_lock();
 			agt = trace_ust_find_agent(session->ust_session, app->domain);
 			if (agt) {
 				agent_update(agt, app->sock->fd);
 			}
+			rcu_read_unlock();
 		}
 		session_unlock(session);
 	}
diff --git a/src/bin/lttng-sessiond/trace-ust.c b/src/bin/lttng-sessiond/trace-ust.c
index ac980fd45..6618cdb09 100644
--- a/src/bin/lttng-sessiond/trace-ust.c
+++ b/src/bin/lttng-sessiond/trace-ust.c
@@ -202,6 +202,9 @@ error:
 /*
  * Lookup an agent in the session agents hash table by domain type and return
  * the object if found else NULL.
+ *
+ * RCU read side lock must be acquired before calling and only released
+ * once the agent is no longer in scope or being used.
  */
 struct agent *trace_ust_find_agent(struct ltt_ust_session *session,
 		enum lttng_domain_type domain_type)