From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Fri, 30 Apr 2021 14:44:44 +0000 (-0400)
Subject: Fix: kernel consumer: signal metadata ready condition variable
X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=commitdiff_plain;h=27585b307a10773445cb3e94b49295ff56e2efdf

Fix: kernel consumer: signal metadata ready condition variable

The behaviour of the kernel consumer does not match that of the user
space consumer. When a live metadata stream goes back to "sleep", it
must broadcast on the metadata_rdv to wake-up any thread that is
performing a metadata sync.

This mismatch causes a hang in the kernel consumer during the kernel
clear tests.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I7c93007b6d08f340881c08f23931582443bfa397
---

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 32f55f0b7..c0d8e0972 100644
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -1647,6 +1647,14 @@ bool is_get_next_check_metadata_available(int tracer_fd)
 	return available;
 }
 
+static
+int signal_metadata(struct lttng_consumer_stream *stream,
+		struct lttng_consumer_local_data *ctx)
+{
+	ASSERT_LOCKED(stream->metadata_rdv_lock);
+	return pthread_cond_broadcast(&stream->metadata_rdv) ? -errno : 0;
+}
+
 static
 int lttng_kconsumer_set_stream_ops(
 		struct lttng_consumer_stream *stream)
@@ -1677,6 +1685,8 @@ int lttng_kconsumer_set_stream_ops(
 			metadata_bucket_destroy(stream->metadata_bucket);
 			stream->metadata_bucket = NULL;
 		}
+
+		stream->read_subbuffer_ops.on_sleep = signal_metadata;
 	}
 
 	if (!stream->read_subbuffer_ops.get_next_subbuffer) {