[lttng-dev] [PATCH lttng-tools 3/3] Fix: Stream allocation and insertion consistency
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Wed Oct 3 12:38:29 EDT 2012
* 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
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