Fix: hash table cleanup call_rcu deadlock

[lttng-tools.git] / src / bin / lttng-sessiond / ust-app.c

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index 396ca936e004d751633fb6a8fce41cfd9c0b61cd..37f6442156ff03a8724ef62137e66b1548544f30 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -38,6 +38,7 @@
 #include "ust-app.h"
 #include "ust-consumer.h"
 #include "ust-ctl.h"
+#include "utils.h"
 
 /* Next available channel key. */
 static unsigned long next_channel_key;
@@ -307,9 +308,9 @@ void delete_ust_app_stream(int sock, struct ust_app_stream *stream)
 
 /*
  * We need to execute ht_destroy outside of RCU read-side critical
- * section, so we postpone its execution using call_rcu. It is simpler
- * than to change the semantic of the many callers of
- * delete_ust_app_channel().
+ * section and outside of call_rcu thread, so we postpone its execution
+ * using ht_cleanup_push. It is simpler than to change the semantic of
+ * the many callers of delete_ust_app_session().
  */
 static
 void delete_ust_app_channel_rcu(struct rcu_head *head)
@@ -317,8 +318,8 @@ void delete_ust_app_channel_rcu(struct rcu_head *head)
        struct ust_app_channel *ua_chan =
                caa_container_of(head, struct ust_app_channel, rcu_head);
 
-       lttng_ht_destroy(ua_chan->ctx);
-       lttng_ht_destroy(ua_chan->events);
+       ht_cleanup_push(ua_chan->ctx);
+       ht_cleanup_push(ua_chan->events);
        free(ua_chan);
 }
 
@@ -583,9 +584,9 @@ end:
 
 /*
  * We need to execute ht_destroy outside of RCU read-side critical
- * section, so we postpone its execution using call_rcu. It is simpler
- * than to change the semantic of the many callers of
- * delete_ust_app_session().
+ * section and outside of call_rcu thread, so we postpone its execution
+ * using ht_cleanup_push. It is simpler than to change the semantic of
+ * the many callers of delete_ust_app_session().
  */
 static
 void delete_ust_app_session_rcu(struct rcu_head *head)
@@ -593,7 +594,7 @@ void delete_ust_app_session_rcu(struct rcu_head *head)
        struct ust_app_session *ua_sess =
                caa_container_of(head, struct ust_app_session, rcu_head);
 
-       lttng_ht_destroy(ua_sess->channels);
+       ht_cleanup_push(ua_sess->channels);
        free(ua_sess);
 }
 
@@ -685,8 +686,8 @@ void delete_ust_app(struct ust_app *app)
                rcu_read_unlock();
        }
 
-       lttng_ht_destroy(app->sessions);
-       lttng_ht_destroy(app->ust_objd);
+       ht_cleanup_push(app->sessions);
+       ht_cleanup_push(app->ust_objd);
 
        /*
         * Wait until we have deleted the application from the sock hash table
@@ -3155,9 +3156,9 @@ void ust_app_clean_list(void)
        rcu_read_unlock();
 
        /* Destroy is done only when the ht is empty */
-       lttng_ht_destroy(ust_app_ht);
-       lttng_ht_destroy(ust_app_ht_by_sock);
-       lttng_ht_destroy(ust_app_ht_by_notify_sock);
+       ht_cleanup_push(ust_app_ht);
+       ht_cleanup_push(ust_app_ht_by_sock);
+       ht_cleanup_push(ust_app_ht_by_notify_sock);
 }
 
 /*
@@ -4475,9 +4476,14 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
                goto error_rcu_unlock;
        }
 
-       /* Lookup channel by UST object descriptor. Should always be found. */
+       /* Lookup channel by UST object descriptor. */
        ua_chan = find_channel_by_objd(app, cobjd);
-       assert(ua_chan);
+       if (!ua_chan) {
+               DBG("Application channel is being teardown. Abort event notify");
+               ret = 0;
+               goto error_rcu_unlock;
+       }
+
        assert(ua_chan->session);
        ua_sess = ua_chan->session;
 
@@ -4581,9 +4587,14 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
                goto error_rcu_unlock;
        }
 
-       /* Lookup channel by UST object descriptor. Should always be found. */
+       /* Lookup channel by UST object descriptor. */
        ua_chan = find_channel_by_objd(app, cobjd);
-       assert(ua_chan);
+       if (!ua_chan) {
+               DBG("Application channel is being teardown. Abort event notify");
+               ret = 0;
+               goto error_rcu_unlock;
+       }
+
        assert(ua_chan->session);
        ua_sess = ua_chan->session;