Fix: Bad error handling when enable channel fails

Fixes #403

Signed-off-by: David Goulet <dgoulet@efficios.com>

diff --git a/src/bin/lttng-sessiond/channel.c b/src/bin/lttng-sessiond/channel.c
index ae53c672c6c2a5792ba981324f37097e7f596f6d..559c3d154034193381357540e0c0bc7a01f30ce0 100644 (file)
--- a/src/bin/lttng-sessiond/channel.c
+++ b/src/bin/lttng-sessiond/channel.c
@@ -190,8 +190,16 @@ int channel_ust_enable(struct ltt_ust_session *usess, int domain,
        switch (domain) {
        case LTTNG_DOMAIN_UST:
                DBG2("Channel %s being enabled in UST global domain", uchan->name);
-               /* Enable channel for global domain */
-               ret = ust_app_enable_channel_glb(usess, uchan);
+
+               /*
+                * Enable channel for UST global domain on all applications. Ignore
+                * return value here since whatever error we got, it means that the
+                * channel was not created on one or many registered applications and
+                * we can not report this to the user yet. However, at this stage, the
+                * channel was successfully created on the session daemon side so the
+                * enable-channel command is a success.
+                */
+               (void) ust_app_create_channel_glb(usess, uchan);
                break;
 #if 0
        case LTTNG_DOMAIN_UST_PID:
@@ -203,15 +211,6 @@ int channel_ust_enable(struct ltt_ust_session *usess, int domain,
                goto error;
        }
 
-       if (ret < 0) {
-               if (ret != -LTTNG_UST_ERR_EXIST) {
-                       ret = LTTNG_ERR_UST_CHAN_ENABLE_FAIL;
-                       goto error;
-               } else {
-                       ret = LTTNG_OK;
-               }
-       }
-
        uchan->enabled = 1;
        DBG2("Channel %s enabled successfully", uchan->name);
 

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index 6076830099847be986b91be5378d9846c63d63b2..70a647608a3f8881e36a9e22b004ef66cdbc35dd 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -1212,11 +1212,12 @@ error:
 }
 
 /*
- * Create UST app channel and create it on the tracer.
+ * Create UST app channel and create it on the tracer. Set ua_chanp of the
+ * newly created channel if not NULL.
  */
-static struct ust_app_channel *create_ust_app_channel(
-               struct ust_app_session *ua_sess, struct ltt_ust_channel *uchan,
-               struct ust_app *app)
+static int create_ust_app_channel(struct ust_app_session *ua_sess,
+               struct ltt_ust_channel *uchan, struct ust_app *app,
+               struct ust_app_channel **ua_chanp)
 {
        int ret = 0;
        struct lttng_ht_iter iter;
@@ -1234,6 +1235,7 @@ static struct ust_app_channel *create_ust_app_channel(
        ua_chan = alloc_ust_app_channel(uchan->name, &uchan->attr);
        if (ua_chan == NULL) {
                /* Only malloc can fail here */
+               ret = -ENOMEM;
                goto error;
        }
        shadow_copy_channel(ua_chan, uchan);
@@ -1245,17 +1247,23 @@ static struct ust_app_channel *create_ust_app_channel(
                goto error;
        }
 
+       /* Only add the channel if successful on the tracer side. */
        lttng_ht_add_unique_str(ua_sess->channels, &ua_chan->node);
 
        DBG2("UST app create channel %s for PID %d completed", ua_chan->name,
                        app->pid);
 
 end:
-       return ua_chan;
+       if (ua_chanp) {
+               *ua_chanp = ua_chan;
+       }
+
+       /* Everything went well. */
+       return 0;
 
 error:
        delete_ust_app_channel(-1, ua_chan);
-       return NULL;
+       return ret;
 }
 
 /*
@@ -2021,7 +2029,6 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
        struct lttng_ht_iter iter;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
-       struct ust_app_channel *ua_chan;
 
        /* Very wrong code flow */
        assert(usess);
@@ -2049,19 +2056,21 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                ua_sess = create_ust_app_session(usess, app);
                if (ua_sess == NULL) {
                        /* The malloc() failed. */
-                       ret = -1;
+                       ret = -ENOMEM;
                        goto error_rcu_unlock;
                } else if (ua_sess == (void *) -1UL) {
-                       /* The application's socket is not valid. Contiuing */
-                       ret = -1;
+                       /*
+                        * The application's socket is not valid. Either a bad socket or a
+                        * timeout on it. We can't inform yet the caller that for a
+                        * specific app, the session failed so we continue here.
+                        */
                        continue;
                }
 
-               /* Create channel onto application */
-               ua_chan = create_ust_app_channel(ua_sess, uchan, app);
-               if (ua_chan == NULL) {
-                       /* Major problem here and it's maybe the tracer or malloc() */
-                       ret = -1;
+               /* Create channel onto application. We don't need the chan ref. */
+               ret = create_ust_app_channel(ua_sess, uchan, app, NULL);
+               if (ret < 0 && ret == -ENOMEM) {
+                       /* No more memory is a fatal error. Stop right now. */
                        goto error_rcu_unlock;
                }
        }