From 73eff54f86848c2b6f2206244620d42fbadfab09 Mon Sep 17 00:00:00 2001
From: Florian Forster <octo@collectd.org>
Date: Mon, 19 Feb 2024 23:30:49 +0100
Subject: [PATCH] write_prometheus plugin: Fix a deadlock due to a leaked
 mutex.

---
 src/write_prometheus.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/write_prometheus.c b/src/write_prometheus.c
index 893d680a70..edeef4d46d 100644
--- a/src/write_prometheus.c
+++ b/src/write_prometheus.c
@@ -824,8 +824,10 @@ static int prom_missing(metric_family_t const *fam,
   pthread_mutex_lock(&prom_metrics_lock);
 
   metric_family_t *prom_fam = NULL;
-  if (c_avl_get(prom_metrics, fam->name, (void *)&prom_fam) != 0)
+  if (c_avl_get(prom_metrics, fam->name, (void *)&prom_fam) != 0) {
+    pthread_mutex_unlock(&prom_metrics_lock);
     return 0;
+  }
 
   for (size_t i = 0; i < fam->metric.num; i++) {
     metric_t const *m = &fam->metric.ptr[i];