[lttng-dev] [PATCH lttng-tools 1/2] Fix: sessiond: only send streams to consumer once

[Mathieu Desnoyers]

Session daemon should not send streams to consumer daemon
repeatedly when CPU hotplug is performed while doing kernel
tracing.

This causes the consumer daemon to have multiple file descriptors
on the same stream, and thus try to perform operations like reading
a sub-buffer and checking for data pending concurrently. This triggers
safety-net warnings in the kernel tracer.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
---
 src/bin/lttng-sessiond/kernel-consumer.c | 3 ++-
 src/bin/lttng-sessiond/trace-kernel.h    | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/bin/lttng-sessiond/kernel-consumer.c b/src/bin/lttng-sessiond/kernel-consumer.c
index 7582d80..b9d689f 100644
--- a/src/bin/lttng-sessiond/kernel-consumer.c
+++ b/src/bin/lttng-sessiond/kernel-consumer.c
@@ -338,7 +338,7 @@ int kernel_consumer_send_channel_stream(struct consumer_socket *sock,
 
 	/* Send streams */
 	cds_list_for_each_entry(stream, &channel->stream_list.head, list) {
-		if (!stream->fd) {
+		if (!stream->fd || stream->sent_to_consumer) {
 			continue;
 		}
 
@@ -348,6 +348,7 @@ int kernel_consumer_send_channel_stream(struct consumer_socket *sock,
 		if (ret < 0) {
 			goto error;
 		}
+		stream->sent_to_consumer = 1;
 	}
 
 error:
diff --git a/src/bin/lttng-sessiond/trace-kernel.h b/src/bin/lttng-sessiond/trace-kernel.h
index b9bcbfa..91672bc 100644
--- a/src/bin/lttng-sessiond/trace-kernel.h
+++ b/src/bin/lttng-sessiond/trace-kernel.h
@@ -84,6 +84,7 @@ struct ltt_kernel_stream {
 	int fd;
 	int state;
 	int cpu;
+	int sent_to_consumer;
 	/* Format is %s_%d respectively channel name and CPU number. */
 	char name[DEFAULT_STREAM_NAME_LEN];
 	uint64_t tracefile_size;
-- 
2.1.4