X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fust-app.c;h=8508a6e7c286f954e475422638e239ecbc833c58;hb=445fe60d5571382fd203cfb4ab32030e29fc490b;hp=8f0b7faf7bba62b5318dfc54f1efa5df21c08da9;hpb=7a391832ea3d70a71e00b76398259c5aa7d18541;p=lttng-tools.git diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c index 8f0b7faf7..8508a6e7c 100644 --- a/src/bin/lttng-sessiond/ust-app.c +++ b/src/bin/lttng-sessiond/ust-app.c @@ -425,8 +425,9 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan, /* * Push metadata to consumer socket. * - * The socket lock MUST be acquired. - * The ust app session lock MUST be acquired. + * RCU read-side lock must be held to guarantee existance of socket. + * Must be called with the ust app session lock held. + * Must be called with the registry lock held. * * On success, return the len of metadata pushed or else a negative value. */ @@ -441,25 +442,22 @@ ssize_t ust_app_push_metadata(struct ust_registry_session *registry, assert(registry); assert(socket); - pthread_mutex_lock(®istry->lock); - /* - * Means that no metadata was assigned to the session. This can happens if - * no start has been done previously. + * Means that no metadata was assigned to the session. This can + * happens if no start has been done previously. */ if (!registry->metadata_key) { - pthread_mutex_unlock(®istry->lock); return 0; } /* - * On a push metadata error either the consumer is dead or the metadata - * channel has been destroyed because its endpoint might have died (e.g: - * relayd). If so, the metadata closed flag is set to 1 so we deny pushing - * metadata again which is not valid anymore on the consumer side. + * On a push metadata error either the consumer is dead or the + * metadata channel has been destroyed because its endpoint + * might have died (e.g: relayd). If so, the metadata closed + * flag is set to 1 so we deny pushing metadata again which is + * not valid anymore on the consumer side. */ if (registry->metadata_closed) { - pthread_mutex_unlock(®istry->lock); return -EPIPE; } @@ -488,29 +486,32 @@ ssize_t ust_app_push_metadata(struct ust_registry_session *registry, registry->metadata_len_sent += len; push_data: - pthread_mutex_unlock(®istry->lock); ret = consumer_push_metadata(socket, registry->metadata_key, metadata_str, len, offset); if (ret < 0) { /* - * There is an acceptable race here between the registry metadata key - * assignment and the creation on the consumer. The session daemon can - * concurrently push metadata for this registry while being created on - * the consumer since the metadata key of the registry is assigned - * *before* it is setup to avoid the consumer to ask for metadata that - * could possibly be not found in the session daemon. + * There is an acceptable race here between the registry + * metadata key assignment and the creation on the + * consumer. The session daemon can concurrently push + * metadata for this registry while being created on the + * consumer since the metadata key of the registry is + * assigned *before* it is setup to avoid the consumer + * to ask for metadata that could possibly be not found + * in the session daemon. * - * The metadata will get pushed either by the session being stopped or - * the consumer requesting metadata if that race is triggered. + * The metadata will get pushed either by the session + * being stopped or the consumer requesting metadata if + * that race is triggered. */ if (ret == -LTTCOMM_CONSUMERD_CHANNEL_FAIL) { ret = 0; } - /* Update back the actual metadata len sent since it failed here. */ - pthread_mutex_lock(®istry->lock); + /* + * Update back the actual metadata len sent since it + * failed here. + */ registry->metadata_len_sent -= len; - pthread_mutex_unlock(®istry->lock); ret_val = ret; goto error_push; } @@ -522,13 +523,14 @@ end: error: if (ret_val) { /* - * On error, flag the registry that the metadata is closed. We were unable - * to push anything and this means that either the consumer is not - * responding or the metadata cache has been destroyed on the consumer. + * On error, flag the registry that the metadata is + * closed. We were unable to push anything and this + * means that either the consumer is not responding or + * the metadata cache has been destroyed on the + * consumer. */ registry->metadata_closed = 1; } - pthread_mutex_unlock(®istry->lock); error_push: free(metadata_str); return ret_val; @@ -540,7 +542,8 @@ error_push: * socket to send the metadata is retrieved from consumer, if sock * is not NULL we use it to send the metadata. * RCU read-side lock must be held while calling this function, - * therefore ensuring existance of registry. + * therefore ensuring existance of registry. It also ensures existance + * of socket throughout this function. * * Return 0 on success else a negative error. */ @@ -555,49 +558,37 @@ static int push_metadata(struct ust_registry_session *registry, assert(consumer); pthread_mutex_lock(®istry->lock); - if (registry->metadata_closed) { - pthread_mutex_unlock(®istry->lock); - return -EPIPE; + ret_val = -EPIPE; + goto error; } /* Get consumer socket to use to push the metadata.*/ socket = consumer_find_socket_by_bitness(registry->bits_per_long, consumer); - pthread_mutex_unlock(®istry->lock); if (!socket) { ret_val = -1; goto error; } - /* - * TODO: Currently, we hold the socket lock around sampling of the next - * metadata segment to ensure we send metadata over the consumer socket in - * the correct order. This makes the registry lock nest inside the socket - * lock. - * - * Please note that this is a temporary measure: we should move this lock - * back into ust_consumer_push_metadata() when the consumer gets the - * ability to reorder the metadata it receives. - */ - pthread_mutex_lock(socket->lock); ret = ust_app_push_metadata(registry, socket, 0); - pthread_mutex_unlock(socket->lock); if (ret < 0) { ret_val = ret; goto error; } - + pthread_mutex_unlock(®istry->lock); return 0; error: +end: + pthread_mutex_unlock(®istry->lock); return ret_val; } /* * Send to the consumer a close metadata command for the given session. Once * done, the metadata channel is deleted and the session metadata pointer is - * nullified. The session lock MUST be acquired here unless the application is + * nullified. The session lock MUST be held unless the application is * in the destroy path. * * Return 0 on success else a negative value.