From 4ee10a6c20802ecc2d1f933f4686334a7626deec Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Thu, 24 Aug 2023 17:48:09 +0200
Subject: [PATCH] GelfWriter: protect m_Stream via m_WorkQueue, not
 ObjectLock(this)

On shutdown or HA re-connect ConfigObject#SetAuthority(false) is called which
does ObjectLock(this) and ConfigObject#Pause(). GelfWriter#Pause(), with the
above ObjectLock, calls m_WorkQueue.Join(). But items inside that also doing
ObjectLock(this) cause a deadlock.
---
 lib/perfdata/gelfwriter.cpp | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/lib/perfdata/gelfwriter.cpp b/lib/perfdata/gelfwriter.cpp
index 79e76aaa3..c5b2bbd13 100644
--- a/lib/perfdata/gelfwriter.cpp
+++ b/lib/perfdata/gelfwriter.cpp
@@ -114,18 +114,17 @@ void GelfWriter::Pause()
 
 	m_ReconnectTimer->Stop(true);
 
-	try {
-		ReconnectInternal();
-	} catch (const std::exception&) {
-		Log(LogInformation, "GelfWriter")
-			<< "'" << GetName() << "' paused. Unable to connect, not flushing buffers. Data may be lost on reload.";
-
-		ObjectImpl<GelfWriter>::Pause();
-		return;
-	}
+	m_WorkQueue.Enqueue([this]() {
+		try {
+			ReconnectInternal();
+		} catch (const std::exception&) {
+			Log(LogInformation, "GelfWriter")
+				<< "Unable to connect, not flushing buffers. Data may be lost.";
+		}
+	}, PriorityImmediate);
 
+	m_WorkQueue.Enqueue([this]() { DisconnectInternal(); }, PriorityLow);
 	m_WorkQueue.Join();
-	DisconnectInternal();
 
 	Log(LogInformation, "GelfWriter")
 		<< "'" << GetName() << "' paused.";
@@ -513,8 +512,6 @@ void GelfWriter::SendLogMessage(const Checkable::Ptr& checkable, const String& g
 
 	String log = msgbuf.str();
 
-	ObjectLock olock(this);
-
 	if (!GetConnected())
 		return;