Cleanup: document RCU read-side lock better

Eventually we will have to move rcu read-side lock within the callees,
but let's at least make the current code consistent.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 03c00a677ac4f53702dd79c68cc2759b897bdd4f..8c15c7e135016098f3cb90a94923ec9eb3fc9d93 100644 (file)
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -581,6 +581,7 @@ static int flush_channel(uint64_t chan_key)
 
        DBG("UST consumer flush channel key %" PRIu64, chan_key);
 
+       rcu_read_lock();
        channel = consumer_find_channel(chan_key);
        if (!channel) {
                ERR("UST consumer flush channel %" PRIu64 " not found", chan_key);
@@ -591,20 +592,19 @@ static int flush_channel(uint64_t chan_key)
        ht = consumer_data.stream_per_chan_id_ht;
 
        /* For each stream of the channel id, flush it. */
-       rcu_read_lock();
        cds_lfht_for_each_entry_duplicate(ht->ht,
                        ht->hash_fct(&channel->key, lttng_ht_seed), ht->match_fct,
                        &channel->key, &iter.iter, stream, node_channel_id.node) {
                        ustctl_flush_buffer(stream->ustream, 1);
        }
-       rcu_read_unlock();
-
 error:
+       rcu_read_unlock();
        return ret;
 }
 
 /*
  * Close metadata stream wakeup_fd using the given key to retrieve the channel.
+ * RCU read side lock MUST be acquired before calling this function.
  *
  * Return 0 on success else an LTTng error code.
  */