From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Thu, 2 Apr 2020 04:57:38 +0000 (-0400)
Subject: Fix: consumer: fallback to flush when flush empty is unsupported
X-Git-Tag: v2.12.0~24
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=a59154c54172a22729795743bfed37d7d6ae771d;p=lttng-tools.git

Fix: consumer: fallback to flush when flush empty is unsupported

Session destruction fails on older (<= 2.8) lttng-modules as the
flush_empty fails on the kernel streams during the quiet rotation.

Fallback to the regular flush as the semantics of regular rotations
are not expected here; we merely want to flush any pending data and
destroy the session.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ifdf8a4e60b55dbf582747d71f5c2485d24c11964
---

diff --git a/src/common/consumer/consumer.c b/src/common/consumer/consumer.c
index 4613284a8..c043353b9 100644
--- a/src/common/consumer/consumer.c
+++ b/src/common/consumer/consumer.c
@@ -3953,8 +3953,18 @@ int consumer_flush_buffer(struct lttng_consumer_stream *stream, int producer_act
 		} else {
 			ret = kernctl_buffer_flush_empty(stream->wait_fd);
 			if (ret < 0) {
-				ERR("Failed to flush kernel stream");
-				goto end;
+				/*
+				 * Doing a buffer flush which does not take into
+				 * account empty packets. This is not perfect,
+				 * but required as a fall-back when
+				 * "flush_empty" is not implemented by
+				 * lttng-modules.
+				 */
+				ret = kernctl_buffer_flush(stream->wait_fd);
+				if (ret < 0) {
+					ERR("Failed to flush kernel stream");
+					goto end;
+				}
 			}
 		}
 		break;