Fix: protect consumer_find_channel with rcu locking

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

diff --git a/src/common/consumer.c b/src/common/consumer.c
index 0e73bc9b8aeda6766953fbd381fcc05c370f795c..51f861e23695c642a56a943aa272fb24c89c7a5d 100644 (file)
--- a/src/common/consumer.c
+++ b/src/common/consumer.c
@@ -127,6 +127,12 @@ void consumer_steal_stream_key(int key, struct lttng_ht *ht)
        rcu_read_unlock();
 }
 
+/*
+ * Return a channel object for the given key.
+ *
+ * RCU read side lock MUST be acquired before calling this function and
+ * protects the channel ptr.
+ */
 static struct lttng_consumer_channel *consumer_find_channel(int key)
 {
        struct lttng_ht_iter iter;
@@ -138,8 +144,6 @@ static struct lttng_consumer_channel *consumer_find_channel(int key)
                return NULL;
        }
 
-       rcu_read_lock();
-
        lttng_ht_lookup(consumer_data.channel_ht, (void *)((unsigned long) key),
                        &iter);
        node = lttng_ht_iter_get_node_ulong(&iter);
@@ -147,8 +151,6 @@ static struct lttng_consumer_channel *consumer_find_channel(int key)
                channel = caa_container_of(node, struct lttng_consumer_channel, node);
        }
 
-       rcu_read_unlock();
-
        return channel;
 }
 
@@ -475,6 +477,8 @@ struct lttng_consumer_stream *consumer_allocate_stream(
                goto end;
        }
 
+       rcu_read_lock();
+
        /*
         * Get stream's channel reference. Needed when adding the stream to the
         * global hash table.
@@ -531,9 +535,12 @@ struct lttng_consumer_stream *consumer_allocate_stream(
                        stream->path_name, stream->key, stream->shm_fd, stream->wait_fd,
                        (unsigned long long) stream->mmap_len, stream->out_fd,
                        stream->net_seq_idx, stream->session_id);
+
+       rcu_read_unlock();
        return stream;
 
 error:
+       rcu_read_unlock();
        free(stream);
 end:
        return NULL;