From: Yannick Lamarre <ylamarre@efficios.com>
Date: Thu, 25 Apr 2019 22:23:31 +0000 (-0400)
Subject: Fix: hang in thread_rotation when using compat-poll
X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=commitdiff_plain;h=ca3833f638213d2cf0604481fade27b4437dc985

Fix: hang in thread_rotation when using compat-poll

Add missing verification to prevent a blocking read on an empty fd.

Signed-off-by: Yannick Lamarre <ylamarre@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/rotation-thread.c b/src/bin/lttng-sessiond/rotation-thread.c
index 6669372dd..b86b16689 100644
--- a/src/bin/lttng-sessiond/rotation-thread.c
+++ b/src/bin/lttng-sessiond/rotation-thread.c
@@ -974,6 +974,10 @@ void *thread_rotation(void *data)
 			int fd = LTTNG_POLL_GETFD(&thread.events, i);
 			uint32_t revents = LTTNG_POLL_GETEV(&thread.events, i);
 
+			if (!revents) {
+				/* No activity for this FD (poll implementation). */
+				continue;
+			}
 			DBG("[rotation-thread] Handling fd (%i) activity (%u)",
 					fd, revents);