From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 16 Jul 2013 01:17:06 +0000 (-0400)
Subject: lttng_ustconsumer_recv_metadata does not need all those locks
X-Git-Tag: v2.3.0-rc1~16
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=f82d9449a304561c5914b2c5f9471a640ca99248

lttng_ustconsumer_recv_metadata does not need all those locks

Since lttng_ustconsumer_recv_metadata() does not push data into the
stream anymore, it only needs the metadata cache lock.

Reviewed-by: Julien Desfossez <julien.desfossez@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/src/common/consumer-timer.c b/src/common/consumer-timer.c
index a32dbf64d..a7f4536a2 100644
--- a/src/common/consumer-timer.c
+++ b/src/common/consumer-timer.c
@@ -82,9 +82,7 @@ static void metadata_switch_timer(struct lttng_consumer_local_data *ctx,
 		 * Locks taken by lttng_ustconsumer_request_metadata():
 		 * - metadata_socket_lock
 		 *   - Calling lttng_ustconsumer_recv_metadata():
-		 *     - consumer_data.lock
-		 *       - channel->lock
-		 *         - channel->metadata_cache->lock
+		 *     - channel->metadata_cache->lock
 		 *     - Calling consumer_metadata_cache_flushed():
 		 *       - consumer_data.lock
 		 *         - channel->lock
diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 986826fca..21d7050b6 100644
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -1039,17 +1039,6 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
 		goto end_free;
 	}
 
-	/*
-	 * XXX: The consumer data lock is acquired before calling metadata cache
-	 * write which calls push metadata that MUST be protected by the consumer
-	 * lock in order to be able to check the validity of the metadata stream of
-	 * the channel.
-	 *
-	 * Note that this will be subject to change to better fine grained locking
-	 * and ultimately try to get rid of this global consumer data lock.
-	 */
-	pthread_mutex_lock(&consumer_data.lock);
-	pthread_mutex_lock(&channel->lock);
 	pthread_mutex_lock(&channel->metadata_cache->lock);
 	ret = consumer_metadata_cache_write(channel, offset, len, metadata_str);
 	if (ret < 0) {
@@ -1061,13 +1050,9 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
 		 * waiting for the metadata cache to be flushed.
 		 */
 		pthread_mutex_unlock(&channel->metadata_cache->lock);
-		pthread_mutex_unlock(&channel->lock);
-		pthread_mutex_unlock(&consumer_data.lock);
 		goto end_free;
 	}
 	pthread_mutex_unlock(&channel->metadata_cache->lock);
-	pthread_mutex_unlock(&channel->lock);
-	pthread_mutex_unlock(&consumer_data.lock);
 
 	while (consumer_metadata_cache_flushed(channel, offset + len)) {
 		DBG("Waiting for metadata to be flushed");