From f1dc10573faec3e0f729ba1776fe4730bf248943 Mon Sep 17 00:00:00 2001
From: Dale Davies <dale.davies@catalyst-eu.net>
Date: Thu, 10 Aug 2023 13:42:46 +0100
Subject: [PATCH] MDL-80385 core: Check lock state before attempting to acquire
 a lock

This is a cherry-pick of the same change from MDL-76865, which was
accidentally reverted in MDL-79428.
---
 cache/classes/loaders.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/cache/classes/loaders.php b/cache/classes/loaders.php
index c9895806c47..9754d4ec346 100644
--- a/cache/classes/loaders.php
+++ b/cache/classes/loaders.php
@@ -621,7 +621,8 @@ class cache implements cache_loader {
         // store; parent method will have set it to all stores if needed.
         if ($setaftervalidation) {
             $lock = null;
-            if (!empty($this->requirelockingbeforewrite)) {
+            // Only try to acquire a lock for this cache if we do not already have one.
+            if (!empty($this->requirelockingbeforewrite) && !$this->check_lock_state($key)) {
                 $lock = $this->acquire_lock($key);
             }
             if ($requiredversion === self::VERSION_NONE) {