Fix: UST consumer need to iterate on streams, just change their key

We need iteration to still be able to see the stream/channel, but not
lookups from sessiond query.

Ensure that teardown does not lookup by key.

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

diff --git a/src/common/consumer.c b/src/common/consumer.c
index 3fcb528d1c0ca87899d6d6142d57829c84cacee4..3d79b5122d82bb3f020f3efe920d86b93c493005 100644 (file)
--- a/src/common/consumer.c
+++ b/src/common/consumer.c
@@ -86,9 +86,18 @@ static void consumer_steal_stream_key(int key)
 {
        struct lttng_consumer_stream *stream;
 
+       rcu_read_lock();
        stream = consumer_find_stream(key);
-       if (stream)
+       if (stream) {
                stream->key = -1;
+               /*
+                * We don't want the lookup to match, but we still need
+                * to iterate on this stream when iterating over the hash table. Just
+                * change the node key.
+                */
+               stream->node.key = -1;
+       }
+       rcu_read_unlock();
 }
 
 static struct lttng_consumer_channel *consumer_find_channel(int key)
@@ -119,9 +128,18 @@ static void consumer_steal_channel_key(int key)
 {
        struct lttng_consumer_channel *channel;
 
+       rcu_read_lock();
        channel = consumer_find_channel(key);
-       if (channel)
+       if (channel) {
                channel->key = -1;
+               /*
+                * We don't want the lookup to match, but we still need
+                * to iterate on this channel when iterating over the hash table. Just
+                * change the node key.
+                */
+               channel->node.key = -1;
+       }
+       rcu_read_unlock();
 }
 
 static
@@ -167,15 +185,9 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
        }
 
        rcu_read_lock();
-
-       /* Get stream node from hash table */
-       lttng_ht_lookup(consumer_data.stream_ht,
-                       (void *)((unsigned long) stream->key), &iter);
-       /*
-        * Remove stream node from hash table. It can fail if it's been
-        * replaced due to key reuse.
-        */
-       (void) lttng_ht_del(consumer_data.stream_ht, &iter);
+       iter.iter.node = &stream->node.node;
+       ret = lttng_ht_del(consumer_data.stream_ht, &iter);
+       assert(!ret);
 
        rcu_read_unlock();
 
@@ -293,12 +305,7 @@ int consumer_add_stream(struct lttng_consumer_stream *stream)
        /* Steal stream identifier, for UST */
        consumer_steal_stream_key(stream->key);
        rcu_read_lock();
-       /*
-        * We simply remove the old channel from the hash table. It's
-        * ok, since we know for sure the sessiond wants to replace it
-        * with the new version, because the key has been reused.
-        */
-       (void) lttng_ht_add_replace_ulong(consumer_data.stream_ht, &stream->node);
+       lttng_ht_add_unique_ulong(consumer_data.stream_ht, &stream->node);
        rcu_read_unlock();
        consumer_data.stream_count++;
        consumer_data.need_update = 1;
@@ -376,16 +383,9 @@ void consumer_del_channel(struct lttng_consumer_channel *channel)
        }
 
        rcu_read_lock();
-
-       lttng_ht_lookup(consumer_data.channel_ht,
-                       (void *)((unsigned long) channel->key), &iter);
-
-       /*
-        * Remove channel node from hash table. It can fail if it's been
-        * replaced due to key reuse.
-        */
-       (void) lttng_ht_del(consumer_data.channel_ht, &iter);
-
+       iter.iter.node = &channel->node.node;
+       ret = lttng_ht_del(consumer_data.channel_ht, &iter);
+       assert(!ret);
        rcu_read_unlock();
 
        if (channel->mmap_base != NULL) {
@@ -472,12 +472,7 @@ int consumer_add_channel(struct lttng_consumer_channel *channel)
        /* Steal channel identifier, for UST */
        consumer_steal_channel_key(channel->key);
        rcu_read_lock();
-       /*
-        * We simply remove the old channel from the hash table. It's
-        * ok, since we know for sure the sessiond wants to replace it
-        * with the new version, because the key has been reused.
-        */
-       (void) lttng_ht_add_replace_ulong(consumer_data.channel_ht, &channel->node);
+       lttng_ht_add_unique_ulong(consumer_data.channel_ht, &channel->node);
        rcu_read_unlock();
        pthread_mutex_unlock(&consumer_data.lock);
 
@@ -1037,8 +1032,6 @@ void *lttng_consumer_thread_poll_fds(void *data)
                                        local_stream[i]->hangup_flush_done) {
                                ssize_t len;
 
-                               assert(!(pollfd[i].revents & POLLERR));
-                               assert(!(pollfd[i].revents & POLLNVAL));
                                DBG("Normal read on fd %d", pollfd[i].fd);
                                len = ctx->on_buffer_ready(local_stream[i], ctx);
                                /* it's ok to have an unavailable sub-buffer */