Fix: RCU unlock out of error path

[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 ec6f998bb7a87e6a6d2cc957a26cf753381c3c66..6076830099847be986b91be5378d9846c63d63b2 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -256,8 +256,7 @@ static
 void delete_ust_app(struct ust_app *app)
 {
        int ret, sock;
-       struct lttng_ht_iter iter;
-       struct ust_app_session *ua_sess;
+       struct ust_app_session *ua_sess, *tmp_ua_sess;
 
        rcu_read_lock();
 
@@ -265,17 +264,14 @@ void delete_ust_app(struct ust_app *app)
        sock = app->sock;
        app->sock = -1;
 
+       lttng_ht_destroy(app->sessions);
+
        /* Wipe sessions */
-       cds_lfht_for_each_entry(app->sessions->ht, &iter.iter, ua_sess,
-                       node.node) {
-               ret = lttng_ht_del(app->sessions, &iter);
-               if (ret) {
-                       /* The session is already scheduled for teardown. */
-                       continue;
-               }
-               delete_ust_app_session(app->sock, ua_sess);
+       cds_list_for_each_entry_safe(ua_sess, tmp_ua_sess, &app->teardown_head,
+                       teardown_node) {
+               /* Free every object in the session and the session. */
+               delete_ust_app_session(sock, ua_sess);
        }
-       lttng_ht_destroy(app->sessions);
 
        /*
         * Wait until we have deleted the application from the sock hash table
@@ -1465,6 +1461,8 @@ int ust_app_register(struct ust_register_msg *msg, int sock)
        lta->sock = sock;
        lttng_ht_node_init_ulong(&lta->sock_n, (unsigned long)lta->sock);
 
+       CDS_INIT_LIST_HEAD(&lta->teardown_head);
+
        rcu_read_lock();
 
        /*
@@ -1500,6 +1498,7 @@ void ust_app_unregister(int sock)
        struct ust_app *lta;
        struct lttng_ht_node_ulong *node;
        struct lttng_ht_iter iter;
+       struct ust_app_session *ua_sess;
        int ret;
 
        rcu_read_lock();
@@ -1534,6 +1533,22 @@ void ust_app_unregister(int sock)
                                lta->pid);
        }
 
+       /* Remove sessions so they are not visible during deletion.*/
+       cds_lfht_for_each_entry(lta->sessions->ht, &iter.iter, ua_sess,
+                       node.node) {
+               ret = lttng_ht_del(lta->sessions, &iter);
+               if (ret) {
+                       /* The session was already removed so scheduled for teardown. */
+                       continue;
+               }
+
+               /*
+                * Add session to list for teardown. This is safe since at this point we
+                * are the only one using this list.
+                */
+               cds_list_add(&ua_sess->teardown_node, &lta->teardown_head);
+       }
+
        /* Free memory */
        call_rcu(&lta->pid_n.head, delete_ust_app_rcu);
 
@@ -2035,7 +2050,7 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                if (ua_sess == NULL) {
                        /* The malloc() failed. */
                        ret = -1;
-                       goto error;
+                       goto error_rcu_unlock;
                } else if (ua_sess == (void *) -1UL) {
                        /* The application's socket is not valid. Contiuing */
                        ret = -1;
@@ -2047,13 +2062,12 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                if (ua_chan == NULL) {
                        /* Major problem here and it's maybe the tracer or malloc() */
                        ret = -1;
-                       goto error;
+                       goto error_rcu_unlock;
                }
        }
 
+error_rcu_unlock:
        rcu_read_unlock();
-
-error:
        return ret;
 }
 
@@ -2206,7 +2220,8 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
 
        ua_sess = lookup_session_by_app(usess, app);
        if (ua_sess == NULL) {
-               goto error_rcu_unlock;
+               /* The session is in teardown process. Ignore and continue. */
+               goto end;
        }
 
        /* Upon restart, we skip the setup, already done */
@@ -2364,8 +2379,7 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 
        ua_sess = lookup_session_by_app(usess, app);
        if (ua_sess == NULL) {
-               /* Only malloc can failed so something is really wrong */
-               goto error_rcu_unlock;
+               goto end;
        }
 
        /*
@@ -2427,7 +2441,7 @@ error_rcu_unlock:
 /*
  * Destroy a specific UST session in apps.
  */
-int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
+static int destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 {
        struct ust_app_session *ua_sess;
        struct lttng_ust_object_data obj;
@@ -2446,8 +2460,8 @@ int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
        __lookup_session_by_app(usess, app, &iter);
        node = lttng_ht_iter_get_node_ulong(&iter);
        if (node == NULL) {
-               /* Only malloc can failed so something is really wrong */
-               goto error_rcu_unlock;
+               /* Session is being or is deleted. */
+               goto end;
        }
        ua_sess = caa_container_of(node, struct ust_app_session, node);
        ret = lttng_ht_del(app->sessions, &iter);
@@ -2473,11 +2487,6 @@ end:
        rcu_read_unlock();
        health_code_update(&health_thread_cmd);
        return 0;
-
-error_rcu_unlock:
-       rcu_read_unlock();
-       health_code_update(&health_thread_cmd);
-       return -1;
 }
 
 /*
@@ -2546,7 +2555,7 @@ int ust_app_destroy_trace_all(struct ltt_ust_session *usess)
        rcu_read_lock();
 
        cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
-               ret = ust_app_destroy_trace(usess, app);
+               ret = destroy_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
                        continue;
@@ -2571,10 +2580,7 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
        struct ust_app_event *ua_event;
        struct ust_app_ctx *ua_ctx;
 
-       if (usess == NULL) {
-               ERR("No UST session on global update. Returning");
-               goto error;
-       }
+       assert(usess);
 
        DBG2("UST app global update for app sock %d for session id %d", sock,
                        usess->id);