From 91732e7c55ba8177b34c989ab3c9936864e6f954 Mon Sep 17 00:00:00 2001
From: Andy Heninger <andy.heninger@gmail.com>
Date: Tue, 8 Feb 2022 16:31:34 -0800
Subject: [PATCH] ICU-21832 Remove unsafe double-checked lock in ICUNotifier

ICUNotifier::notifyChanged() was using the thread-unsafe double-checked lock
idiom. Replace it with use of the mutex only.
---
 icu4c/source/common/servnotf.cpp | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/icu4c/source/common/servnotf.cpp b/icu4c/source/common/servnotf.cpp
index 10183d3a2dc..d9fb3887520 100644
--- a/icu4c/source/common/servnotf.cpp
+++ b/icu4c/source/common/servnotf.cpp
@@ -106,13 +106,11 @@ ICUNotifier::removeListener(const EventListener *l, UErrorCode& status)
 void 
 ICUNotifier::notifyChanged(void) 
 {
+    Mutex lmx(&notifyLock);
     if (listeners != NULL) {
-        Mutex lmx(&notifyLock);
-        if (listeners != NULL) {
-            for (int i = 0, e = listeners->size(); i < e; ++i) {
-                EventListener* el = (EventListener*)listeners->elementAt(i);
-                notifyListener(*el);
-            }
+        for (int i = 0, e = listeners->size(); i < e; ++i) {
+            EventListener* el = (EventListener*)listeners->elementAt(i);
+            notifyListener(*el);
         }
     }
 }