From 410cb65d7ab940e08a76754e8a8664a32ad7c108 Mon Sep 17 00:00:00 2001
From: Steve Fink <sfink@mozilla.com>
Date: Wed, 23 Dec 2020 21:00:44 +0000
Subject: [PATCH] Bug 1682947 - Use MADV_FREE_REUSE before using decommitted
 memory again on OSX, as per
 https://bugs.chromium.org/p/chromium/issues/detail?id=823915 r=glandium

Differential Revision: https://phabricator.services.mozilla.com/D99932
---
 js/src/gc/Memory.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/js/src/gc/Memory.cpp b/js/src/gc/Memory.cpp
index 57145d2f71ef..d59585f0c8ff 100644
--- a/js/src/gc/Memory.cpp
+++ b/js/src/gc/Memory.cpp
@@ -811,6 +811,11 @@ bool MarkPagesUnusedHard(void* region, size_t length) {
 void MarkPagesInUseSoft(void* region, size_t length) {
   CheckDecommit(region, length);
 
+#if defined(XP_DARWIN)
+  while (madvise(region, length, MADV_FREE_REUSE) == -1 && errno == EAGAIN) {
+  }
+#endif
+
   MOZ_MAKE_MEM_UNDEFINED(region, length);
 }