Fix: filter attach vs event enable race

[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 5ebe9917a049bc9ae43ee01fbc6348d2fed2c609..7e4bf94051028f7c361749f0a162a4baee8e53b4 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -1446,7 +1446,32 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
        }
 
        /* If event not enabled, disable it on the tracer */
-       if (ua_event->enabled == 0) {
+       if (ua_event->enabled) {
+               /*
+                * We now need to explicitly enable the event, since it
+                * is now disabled at creation.
+                */
+               ret = enable_ust_event(app, ua_sess, ua_event);
+               if (ret < 0) {
+                       /*
+                        * If we hit an EPERM, something is wrong with our enable call. If
+                        * we get an EEXIST, there is a problem on the tracer side since we
+                        * just created it.
+                        */
+                       switch (ret) {
+                       case -LTTNG_UST_ERR_PERM:
+                               /* Code flow problem */
+                               assert(0);
+                       case -LTTNG_UST_ERR_EXIST:
+                               /* It's OK for our use case. */
+                               ret = 0;
+                               break;
+                       default:
+                               break;
+                       }
+                       goto error;
+               }
+       } else {
                ret = disable_ust_event(app, ua_sess, ua_event);
                if (ret < 0) {
                        /*