From mboxrd@z Thu Jan  1 00:00:00 1970
From: mathieu.desnoyers@efficios.com (Mathieu Desnoyers)
Date: Wed, 3 Oct 2012 12:38:29 -0400
Subject: [lttng-dev] [PATCH lttng-tools 3/3] Fix: Stream allocation
	and	insertion consistency
In-Reply-To: <1349279317-28056-3-git-send-email-dgoulet@efficios.com>
References: <1349279317-28056-1-git-send-email-dgoulet@efficios.com>
	<1349279317-28056-3-git-send-email-dgoulet@efficios.com>
Message-ID: <20121003163829.GC21776@Krystal>

* David Goulet (dgoulet at efficios.com) wrote:
> The stream allocation in the consumer was doing ustctl actions on the
> stream and updating refounts. However, before inserting the stream into

refounts -> refcounts.

> the hash table and polling on the fd for data, an error could occur
> which could stop the stream insertion hence creating multiple fd leaks,
> mem leaks and bad refount state.

refount -> refcount

> 
> Furthermore, the consumer_del_stream now can destroy a stream even if
> that stream is not added to the global hash table. The kernel and UST
> consumer uses it on error between allocation and hash table insertion.

consumer -> consumers
uses -> use

> 
> Signed-off-by: David Goulet <dgoulet at efficios.com>
> ---
>  src/common/consumer.c                        |  219 +++++++++++++++++---------
>  src/common/kernel-consumer/kernel-consumer.c |   13 +-
>  src/common/ust-consumer/ust-consumer.c       |   16 +-
>  src/common/ust-consumer/ust-consumer.h       |    4 +-
>  4 files changed, 172 insertions(+), 80 deletions(-)
> 
> diff --git a/src/common/consumer.c b/src/common/consumer.c
> index 6ee366f..6011622 100644
> --- a/src/common/consumer.c
> +++ b/src/common/consumer.c
> @@ -227,8 +227,8 @@ void consumer_flag_relayd_for_destroy(struct consumer_relayd_sock_pair *relayd)
>  }
>  
>  /*
> - * Remove a stream from the global list protected by a mutex. This
> - * function is also responsible for freeing its data structures.
> + * Remove a stream from the global list protected by a mutex. This function is
> + * also responsible for freeing its data structures.
>   */
>  void consumer_del_stream(struct lttng_consumer_stream *stream)
>  {
> @@ -236,10 +236,46 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
>  	struct lttng_ht_iter iter;
>  	struct lttng_consumer_channel *free_chan = NULL;
>  	struct consumer_relayd_sock_pair *relayd;
> +	struct lttng_ht_node_ulong *node;
>  
>  	assert(stream);
>  
> +	DBG3("Consumer deleting stream %d", stream->key);
> +
>  	pthread_mutex_lock(&consumer_data.lock);
> +	rcu_read_lock();
> +
> +	/*
> +	 * A stream with a key value of -1 means that the stream is in the hash
> +	 * table but can not be looked up. This happens when consumer_add_stream is
> +	 * done and we have a duplicate key before insertion.
> +	 * consumer_steal_stream_key() is called to make sure we can insert a
> +	 * stream even though the index is already present. Since the key is the fd
> +	 * value on the session daemon side, duplicates are possible.
> +	 */
> +	if (stream->key != -1) {
> +		lttng_ht_lookup(consumer_data.stream_ht,
> +				(void *)((unsigned long) stream->key), &iter);
> +		node = lttng_ht_iter_get_node_ulong(&iter);
> +		if (node == NULL) {
> +			rcu_read_unlock();
> +
> +			/*
> +			 * Stream doest not exist in hash table. This can happen if we hit
> +			 * an error after allocation but before adding it to the table. We
> +			 * consider that if the node is not in the hash table and has a
> +			 * valid key, no ustctl/ioctl nor mmap action was done hence
> +			 * jumping to the RCU free.
> +			 */
> +			DBG2("Consumer stream key %d not found during deletion", stream->key);
> +			goto free_stream;
> +		} else {
> +			/* Remove stream from hash table and continue */
> +			ret = lttng_ht_del(consumer_data.stream_ht, &iter);
> +			assert(!ret);
> +		}
> +	}
> +	rcu_read_unlock();

Why are you changing this code ? You add a lookup to get the node you
already receive as parameter. It looks pretty much useless to me.

What you probably want there is to pass a flag to consumer_del_stream()
telling it whether or not it needs to remove the stream from the hash
table, so it can skip the ht_del step accordingly.

Let's discuss this one and, once we understand the intent, we'll
continue on the rest of the patch.

Thanks,

Mathieu

>  
>  	switch (consumer_data.type) {
>  	case LTTNG_CONSUMER_KERNEL:
> @@ -260,20 +296,10 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
>  		goto end;
>  	}
>  
> -	rcu_read_lock();
> -	iter.iter.node = &stream->node.node;
> -	ret = lttng_ht_del(consumer_data.stream_ht, &iter);
> -	assert(!ret);
> -
> -	rcu_read_unlock();
> -
> -	if (consumer_data.stream_count <= 0) {
> -		goto end;
> -	}
> +	/* This should NEVER reach a negative value. */
> +	assert(consumer_data.stream_count >= 0);
>  	consumer_data.stream_count--;
> -	if (!stream) {
> -		goto end;
> -	}
> +
>  	if (stream->out_fd >= 0) {
>  		ret = close(stream->out_fd);
>  		if (ret) {
> @@ -321,7 +347,6 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
>  			destroy_relayd(relayd);
>  		}
>  	}
> -	rcu_read_unlock();
>  
>  	uatomic_dec(&stream->chan->refcount);
>  	if (!uatomic_read(&stream->chan->refcount)
> @@ -329,7 +354,6 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
>  		free_chan = stream->chan;
>  	}
>  
> -	call_rcu(&stream->node.head, consumer_free_stream);
>  end:
>  	consumer_data.need_update = 1;
>  	pthread_mutex_unlock(&consumer_data.lock);
> @@ -337,6 +361,10 @@ end:
>  	if (free_chan) {
>  		consumer_del_channel(free_chan);
>  	}
> +
> +free_stream:
> +	call_rcu(&stream->node.head, consumer_free_stream);
> +	rcu_read_unlock();
>  }
>  
>  struct lttng_consumer_stream *consumer_allocate_stream(
> @@ -353,7 +381,6 @@ struct lttng_consumer_stream *consumer_allocate_stream(
>  		int *alloc_ret)
>  {
>  	struct lttng_consumer_stream *stream;
> -	int ret;
>  
>  	stream = zmalloc(sizeof(*stream));
>  	if (stream == NULL) {
> @@ -372,7 +399,7 @@ struct lttng_consumer_stream *consumer_allocate_stream(
>  		ERR("Unable to find channel for stream %d", stream_key);
>  		goto error;
>  	}
> -	stream->chan->refcount++;
> +
>  	stream->key = stream_key;
>  	stream->shm_fd = shm_fd;
>  	stream->wait_fd = wait_fd;
> @@ -391,35 +418,6 @@ struct lttng_consumer_stream *consumer_allocate_stream(
>  	lttng_ht_node_init_ulong(&stream->node, stream->key);
>  	lttng_ht_node_init_ulong(&stream->waitfd_node, stream->wait_fd);
>  
> -	switch (consumer_data.type) {
> -	case LTTNG_CONSUMER_KERNEL:
> -		break;
> -	case LTTNG_CONSUMER32_UST:
> -	case LTTNG_CONSUMER64_UST:
> -		stream->cpu = stream->chan->cpucount++;
> -		ret = lttng_ustconsumer_allocate_stream(stream);
> -		if (ret) {
> -			*alloc_ret = -EINVAL;
> -			goto error;
> -		}
> -		break;
> -	default:
> -		ERR("Unknown consumer_data type");
> -		*alloc_ret = -EINVAL;
> -		goto error;
> -	}
> -
> -	/*
> -	 * When nb_init_streams reaches 0, we don't need to trigger any action in
> -	 * terms of destroying the associated channel, because the action that
> -	 * causes the count to become 0 also causes a stream to be added. The
> -	 * channel deletion will thus be triggered by the following removal of this
> -	 * stream.
> -	 */
> -	if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
> -		uatomic_dec(&stream->chan->nb_init_streams);
> -	}
> -
>  	DBG3("Allocated stream %s (key %d, shm_fd %d, wait_fd %d, mmap_len %llu,"
>  			" out_fd %d, net_seq_idx %d)", stream->path_name, stream->key,
>  			stream->shm_fd, stream->wait_fd,
> @@ -439,38 +437,66 @@ end:
>  int consumer_add_stream(struct lttng_consumer_stream *stream)
>  {
>  	int ret = 0;
> -	struct lttng_ht_node_ulong *node;
> -	struct lttng_ht_iter iter;
>  	struct consumer_relayd_sock_pair *relayd;
>  
> -	pthread_mutex_lock(&consumer_data.lock);
> -	/* Steal stream identifier, for UST */
> -	consumer_steal_stream_key(stream->key, consumer_data.stream_ht);
> +	assert(stream);
>  
> +	DBG3("Adding consumer stream %d", stream->key);
> +
> +	pthread_mutex_lock(&consumer_data.lock);
>  	rcu_read_lock();
> -	lttng_ht_lookup(consumer_data.stream_ht,
> -			(void *)((unsigned long) stream->key), &iter);
> -	node = lttng_ht_iter_get_node_ulong(&iter);
> -	if (node != NULL) {
> -		rcu_read_unlock();
> -		/* Stream already exist. Ignore the insertion */
> -		goto end;
> -	}
>  
> -	lttng_ht_add_unique_ulong(consumer_data.stream_ht, &stream->node);
> +	switch (consumer_data.type) {
> +	case LTTNG_CONSUMER_KERNEL:
> +		break;
> +	case LTTNG_CONSUMER32_UST:
> +	case LTTNG_CONSUMER64_UST:
> +		stream->cpu = stream->chan->cpucount++;
> +		ret = lttng_ustconsumer_add_stream(stream);
> +		if (ret) {
> +			ret = -EINVAL;
> +			goto error;
> +		}
> +
> +		/* Steal stream identifier only for UST */
> +		consumer_steal_stream_key(stream->key, consumer_data.stream_ht);
> +		break;
> +	default:
> +		ERR("Unknown consumer_data type");
> +		assert(0);
> +		ret = -ENOSYS;
> +		goto error;
> +	}
>  
>  	/* Check and cleanup relayd */
>  	relayd = consumer_find_relayd(stream->net_seq_idx);
>  	if (relayd != NULL) {
>  		uatomic_inc(&relayd->refcount);
>  	}
> -	rcu_read_unlock();
>  
> -	/* Update consumer data */
> +	/* Final operation is to add the stream to the global hash table. */
> +	lttng_ht_add_unique_ulong(consumer_data.stream_ht, &stream->node);
> +
> +	/* Update channel refcount once added without error(s). */
> +	uatomic_inc(&stream->chan->refcount);
> +
> +	/*
> +	 * When nb_init_streams reaches 0, we don't need to trigger any action in
> +	 * terms of destroying the associated channel, because the action that
> +	 * causes the count to become 0 also causes a stream to be added. The
> +	 * channel deletion will thus be triggered by the following removal of this
> +	 * stream.
> +	 */
> +	if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
> +		uatomic_dec(&stream->chan->nb_init_streams);
> +	}
> +
> +	/* Update consumer data once the node is inserted. */
>  	consumer_data.stream_count++;
>  	consumer_data.need_update = 1;
>  
> -end:
> +error:
> +	rcu_read_unlock();
>  	pthread_mutex_unlock(&consumer_data.lock);
>  
>  	return ret;
> @@ -1648,10 +1674,37 @@ static void consumer_del_metadata_stream(struct lttng_consumer_stream *stream)
>   * Action done with the metadata stream when adding it to the consumer internal
>   * data structures to handle it.
>   */
> -static void consumer_add_metadata_stream(struct lttng_consumer_stream *stream)
> +static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
> +		struct lttng_ht *ht)
>  {
> +	int ret = 0;
>  	struct consumer_relayd_sock_pair *relayd;
>  
> +	switch (consumer_data.type) {
> +	case LTTNG_CONSUMER_KERNEL:
> +		break;
> +	case LTTNG_CONSUMER32_UST:
> +	case LTTNG_CONSUMER64_UST:
> +		ret = lttng_ustconsumer_add_stream(stream);
> +		if (ret) {
> +			ret = -EINVAL;
> +			goto error;
> +		}
> +
> +		/* Steal stream identifier only for UST */
> +		consumer_steal_stream_key(stream->key, ht);
> +		break;
> +	default:
> +		ERR("Unknown consumer_data type");
> +		assert(0);
> +		return -ENOSYS;
> +	}
> +
> +	/*
> +	 * From here, refcounts are updated so be _careful_ when returning an error
> +	 * after this point.
> +	 */
> +
>  	/* Find relayd and, if one is found, increment refcount. */
>  	rcu_read_lock();
>  	relayd = consumer_find_relayd(stream->net_seq_idx);
> @@ -1659,6 +1712,27 @@ static void consumer_add_metadata_stream(struct lttng_consumer_stream *stream)
>  		uatomic_inc(&relayd->refcount);
>  	}
>  	rcu_read_unlock();
> +
> +	/* Update channel refcount once added without error(s). */
> +	uatomic_inc(&stream->chan->refcount);
> +
> +	/*
> +	 * When nb_init_streams reaches 0, we don't need to trigger any action in
> +	 * terms of destroying the associated channel, because the action that
> +	 * causes the count to become 0 also causes a stream to be added. The
> +	 * channel deletion will thus be triggered by the following removal of this
> +	 * stream.
> +	 */
> +	if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
> +		uatomic_dec(&stream->chan->nb_init_streams);
> +	}
> +
> +	rcu_read_lock();
> +	lttng_ht_add_unique_ulong(ht, &stream->waitfd_node);
> +	rcu_read_unlock();
> +
> +error:
> +	return ret;
>  }
>  
>  /*
> @@ -1755,17 +1829,16 @@ restart:
>  					DBG("Adding metadata stream %d to poll set",
>  							stream->wait_fd);
>  
> -					rcu_read_lock();
> -					/* The node should be init at this point */
> -					lttng_ht_add_unique_ulong(metadata_ht,
> -							&stream->waitfd_node);
> -					rcu_read_unlock();
> +					ret = consumer_add_metadata_stream(stream, metadata_ht);
> +					if (ret) {
> +						/* Stream was not setup properly. Continuing. */
> +						free(stream);
> +						continue;
> +					}
>  
>  					/* Add metadata stream to the global poll events list */
>  					lttng_poll_add(&events, stream->wait_fd,
>  							LPOLLIN | LPOLLPRI);
> -
> -					consumer_add_metadata_stream(stream);
>  				}
>  
>  				/* Metadata pipe handled. Continue handling the others */
> diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
> index 4d61cc5..878c4ab 100644
> --- a/src/common/kernel-consumer/kernel-consumer.c
> +++ b/src/common/kernel-consumer/kernel-consumer.c
> @@ -206,18 +206,20 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
>  					&new_stream->relayd_stream_id);
>  			pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
>  			if (ret < 0) {
> +				consumer_del_stream(new_stream);
>  				goto end_nosignal;
>  			}
>  		} else if (msg.u.stream.net_index != -1) {
>  			ERR("Network sequence index %d unknown. Not adding stream.",
>  					msg.u.stream.net_index);
> -			free(new_stream);
> +			consumer_del_stream(new_stream);
>  			goto end_nosignal;
>  		}
>  
>  		if (ctx->on_recv_stream) {
>  			ret = ctx->on_recv_stream(new_stream);
>  			if (ret < 0) {
> +				consumer_del_stream(new_stream);
>  				goto end_nosignal;
>  			}
>  		}
> @@ -230,9 +232,16 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
>  			} while (ret < 0 && errno == EINTR);
>  			if (ret < 0) {
>  				PERROR("write metadata pipe");
> +				consumer_del_stream(new_stream);
>  			}
>  		} else {
> -			consumer_add_stream(new_stream);
> +			ret = consumer_add_stream(new_stream);
> +			if (ret) {
> +				ERR("Consumer add stream %d failed. Continuing",
> +						new_stream->key);
> +				consumer_del_stream(new_stream);
> +				goto end_nosignal;
> +			}
>  		}
>  
>  		DBG("Kernel consumer_add_stream (%d)", fd);
> diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
> index 76238a0..e10d540 100644
> --- a/src/common/ust-consumer/ust-consumer.c
> +++ b/src/common/ust-consumer/ust-consumer.c
> @@ -234,12 +234,13 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
>  					&new_stream->relayd_stream_id);
>  			pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
>  			if (ret < 0) {
> +				consumer_del_stream(new_stream);
>  				goto end_nosignal;
>  			}
>  		} else if (msg.u.stream.net_index != -1) {
>  			ERR("Network sequence index %d unknown. Not adding stream.",
>  					msg.u.stream.net_index);
> -			free(new_stream);
> +			consumer_del_stream(new_stream);
>  			goto end_nosignal;
>  		}
>  
> @@ -247,6 +248,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
>  		if (ctx->on_recv_stream) {
>  			ret = ctx->on_recv_stream(new_stream);
>  			if (ret < 0) {
> +				consumer_del_stream(new_stream);
>  				goto end_nosignal;
>  			}
>  		}
> @@ -259,9 +261,17 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
>  			} while (ret < 0 && errno == EINTR);
>  			if (ret < 0) {
>  				PERROR("write metadata pipe");
> +				consumer_del_stream(new_stream);
> +				goto end_nosignal;
>  			}
>  		} else {
> -			consumer_add_stream(new_stream);
> +			ret = consumer_add_stream(new_stream);
> +			if (ret) {
> +				ERR("Consumer add stream %d failed. Continuing",
> +						new_stream->key);
> +				consumer_del_stream(new_stream);
> +				goto end_nosignal;
> +			}
>  		}
>  
>  		DBG("UST consumer_add_stream %s (%d,%d) with relayd id %" PRIu64,
> @@ -373,7 +383,7 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
>  	ustctl_unmap_channel(chan->handle);
>  }
>  
> -int lttng_ustconsumer_allocate_stream(struct lttng_consumer_stream *stream)
> +int lttng_ustconsumer_add_stream(struct lttng_consumer_stream *stream)
>  {
>  	struct lttng_ust_object_data obj;
>  	int ret;
> diff --git a/src/common/ust-consumer/ust-consumer.h b/src/common/ust-consumer/ust-consumer.h
> index 3f76f23..6b507ed 100644
> --- a/src/common/ust-consumer/ust-consumer.h
> +++ b/src/common/ust-consumer/ust-consumer.h
> @@ -49,7 +49,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
>  
>  extern int lttng_ustconsumer_allocate_channel(struct lttng_consumer_channel *chan);
>  extern void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan);
> -extern int lttng_ustconsumer_allocate_stream(struct lttng_consumer_stream *stream);
> +extern int lttng_ustconsumer_add_stream(struct lttng_consumer_stream *stream);
>  extern void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream);
>  
>  int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
> @@ -117,7 +117,7 @@ void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
>  }
>  
>  static inline
> -int lttng_ustconsumer_allocate_stream(struct lttng_consumer_stream *stream)
> +int lttng_ustconsumer_add_stream(struct lttng_consumer_stream *stream)
>  {
>  	return -ENOSYS;
>  }
> -- 
> 1.7.10.4
> 
> 
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com