From a30b70220313bfd8083feee051b4093df0cbdb0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Mierzwa?= <l.mierzwa@gmail.com>
Date: Tue, 6 Apr 2021 15:20:56 +0100
Subject: [PATCH] fix(backend): avoid potential recursive locks

Fixes #2944
---
 CHANGELOG.md                    |  1 +
 internal/alertmanager/models.go | 16 +++++++++-------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8f5ff198d..c65f9809b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 
 - Header values are now sanitised before logging when `log:config` is
   enabled #2930.
+- Fixed a deadlock issue that could cause karma to hang #2944 (@jonaz).
 
 ### Added
 
diff --git a/internal/alertmanager/models.go b/internal/alertmanager/models.go
index 488f51893..1f727c9e0 100644
--- a/internal/alertmanager/models.go
+++ b/internal/alertmanager/models.go
@@ -493,12 +493,16 @@ func (am *Alertmanager) setError(err string) {
 	am.lastError = err
 }
 
-func (am *Alertmanager) Error() string {
+func (am *Alertmanager) getLastError() string {
 	am.lock.RLock()
 	defer am.lock.RUnlock()
+	return am.lastError
+}
 
-	if am.lastError != "" {
-		return am.lastError
+func (am *Alertmanager) Error() string {
+	lastError := am.getLastError()
+	if lastError != "" {
+		return lastError
 	}
 
 	configPeers := clusterMembersFromConfig(am)
@@ -597,10 +601,8 @@ func (am *Alertmanager) ClusterName() string {
 }
 
 func (am *Alertmanager) IsHealthy() bool {
-	am.lock.RLock()
-	defer am.lock.RUnlock()
-
-	return am.lastError == ""
+	lastError := am.getLastError()
+	return lastError == ""
 }
 
 func (am *Alertmanager) IsHealthCheckAlert(alert *models.Alert) (string, *healthCheck) {