From: Willy Tarreau <w@1wt.eu>
Date: Tue, 7 Aug 2018 08:07:15 +0000 (+0200)
Subject: BUG/MEDIUM: threads: fix the no-thread case after the change to the sync point
X-Git-Tag: v1.9-dev2~198
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ab657ce2511c4e19b0191fbe1c98cfd823a3c5d6;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: threads: fix the no-thread case after the change to the sync point

In commit 0c026f4 ("MINOR: threads: add more consistency between certain
variables in no-thread case"), we ensured that we don't have all_threads_mask
zeroed anymore. But one test was missed for the write() to the sync pipe.
This results in a situation where when running single-threaded, once a
server status changes, a wake-up message is written to the pipe and never
consumed, showing a 100% CPU usage.

No backport is needed.
---

diff --git a/src/hathreads.c b/src/hathreads.c
index 69dcab9dcd..16284be14e 100644
--- a/src/hathreads.c
+++ b/src/hathreads.c
@@ -70,7 +70,7 @@ void thread_sync_enable(void)
  */
 void thread_want_sync()
 {
-	if (all_threads_mask) {
+	if (all_threads_mask & (all_threads_mask - 1)) {
 		if (threads_want_sync & tid_bit)
 			return;
 		if (HA_ATOMIC_OR(&threads_want_sync, tid_bit) == tid_bit)