From mboxrd@z Thu Jan  1 00:00:00 1970
From: dgoulet@efficios.com (David Goulet)
Date: Wed, 03 Oct 2012 12:42:10 -0400
Subject: [lttng-dev] [PATCH lttng-tools 3/3] Fix: Stream allocation and
 insertion consistency
In-Reply-To: <20121003163829.GC21776@Krystal>
References: <1349279317-28056-1-git-send-email-dgoulet@efficios.com>
	<1349279317-28056-3-git-send-email-dgoulet@efficios.com>
	<20121003163829.GC21776@Krystal>
Message-ID: <506C6AE2.5060304@efficios.com>

Mathieu Desnoyers:
> * 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.

Yes we can do that instead.

> 
> 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
>