+
+/*
+ * Destroy a kernel channel object. It does not do anything on the tracer side.
+ */
+void kernel_destroy_channel(struct ltt_kernel_channel *kchan)
+{
+ struct ltt_kernel_session *ksess = NULL;
+
+ assert(kchan);
+ assert(kchan->channel);
+
+ DBG3("Kernel destroy channel %s", kchan->channel->name);
+
+ /* Update channel count of associated session. */
+ if (kchan->session) {
+ /* Keep pointer reference so we can update it after the destroy. */
+ ksess = kchan->session;
+ }
+
+ trace_kernel_destroy_channel(kchan);
+
+ /*
+ * At this point the kernel channel is not visible anymore. This is safe
+ * since in order to work on a visible kernel session, the tracing session
+ * lock (ltt_session.lock) MUST be acquired.
+ */
+ if (ksess) {
+ ksess->channel_count--;
+ }
+}
+
+/*
+ * Take a snapshot for a given kernel session.
+ *
+ * Return 0 on success or else return a LTTNG_ERR code.
+ */
+int kernel_snapshot_record(struct ltt_kernel_session *ksess,
+ struct snapshot_output *output, int wait, uint64_t max_size_per_stream)
+{
+ int err, ret, saved_metadata_fd;
+ struct consumer_socket *socket;
+ struct lttng_ht_iter iter;
+ struct ltt_kernel_metadata *saved_metadata;
+
+ assert(ksess);
+ assert(ksess->consumer);
+ assert(output);
+
+ DBG("Kernel snapshot record started");
+
+ /* Save current metadata since the following calls will change it. */
+ saved_metadata = ksess->metadata;
+ saved_metadata_fd = ksess->metadata_stream_fd;
+
+ rcu_read_lock();
+
+ ret = kernel_open_metadata(ksess);
+ if (ret < 0) {
+ ret = LTTNG_ERR_KERN_META_FAIL;
+ goto error;
+ }
+
+ ret = kernel_open_metadata_stream(ksess);
+ if (ret < 0) {
+ ret = LTTNG_ERR_KERN_META_FAIL;
+ goto error_open_stream;
+ }
+
+ /* Send metadata to consumer and snapshot everything. */
+ cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
+ socket, node.node) {
+ struct consumer_output *saved_output;
+ struct ltt_kernel_channel *chan;
+
+ /*
+ * Temporarly switch consumer output for our snapshot output. As long
+ * as the session lock is taken, this is safe.
+ */
+ saved_output = ksess->consumer;
+ ksess->consumer = output->consumer;
+
+ pthread_mutex_lock(socket->lock);
+ /* This stream must not be monitored by the consumer. */
+ ret = kernel_consumer_add_metadata(socket, ksess, 0);
+ pthread_mutex_unlock(socket->lock);
+ /* Put back the saved consumer output into the session. */
+ ksess->consumer = saved_output;
+ if (ret < 0) {
+ ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
+ goto error_consumer;
+ }
+
+ /* For each channel, ask the consumer to snapshot it. */
+ cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+ pthread_mutex_lock(socket->lock);
+ ret = consumer_snapshot_channel(socket, chan->fd, output, 0,
+ ksess->uid, ksess->gid,
+ DEFAULT_KERNEL_TRACE_DIR, wait,
+ max_size_per_stream);
+ pthread_mutex_unlock(socket->lock);
+ if (ret < 0) {
+ ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
+ (void) kernel_consumer_destroy_metadata(socket,
+ ksess->metadata);
+ goto error_consumer;
+ }
+ }
+
+ /* Snapshot metadata, */
+ pthread_mutex_lock(socket->lock);
+ ret = consumer_snapshot_channel(socket, ksess->metadata->fd, output,
+ 1, ksess->uid, ksess->gid,
+ DEFAULT_KERNEL_TRACE_DIR, wait, max_size_per_stream);
+ pthread_mutex_unlock(socket->lock);
+ if (ret < 0) {
+ ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
+ goto error_consumer;
+ }
+
+ /*
+ * The metadata snapshot is done, ask the consumer to destroy it since
+ * it's not monitored on the consumer side.
+ */
+ (void) kernel_consumer_destroy_metadata(socket, ksess->metadata);
+ }
+
+ ret = LTTNG_OK;
+
+error_consumer:
+ /* Close newly opened metadata stream. It's now on the consumer side. */
+ err = close(ksess->metadata_stream_fd);
+ if (err < 0) {
+ PERROR("close snapshot kernel");
+ }
+
+error_open_stream:
+ trace_kernel_destroy_metadata(ksess->metadata);
+error:
+ /* Restore metadata state.*/
+ ksess->metadata = saved_metadata;
+ ksess->metadata_stream_fd = saved_metadata_fd;
+
+ rcu_read_unlock();
+ return ret;
+}