From 316b5113e0dab0bfc8b125926372136789a81d40 Mon Sep 17 00:00:00 2001
From: Alexis Beingessner <a.beingessner@gmail.com>
Date: Thu, 28 Jan 2021 11:05:02 +0000
Subject: [PATCH] Bug 1633239 - make the bitfields on CacheStorageService
 atomic. r=valentin,necko-reviewers

this is only a hypothetical fix to the underlying issue since we don't have a clean trace.

Differential Revision: https://phabricator.services.mozilla.com/D103057
---
 netwerk/cache2/CacheStorageService.cpp | 13 +++++++------
 netwerk/cache2/CacheStorageService.h   |  9 +++++++--
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/netwerk/cache2/CacheStorageService.cpp b/netwerk/cache2/CacheStorageService.cpp
index f4e76df530db..30df87a5cf9d 100644
--- a/netwerk/cache2/CacheStorageService.cpp
+++ b/netwerk/cache2/CacheStorageService.cpp
@@ -64,11 +64,12 @@ typedef nsClassHashtable<nsCStringHashKey, CacheEntryTable> GlobalEntryTables;
  */
 static GlobalEntryTables* sGlobalEntryTables;
 
-CacheMemoryConsumer::CacheMemoryConsumer(uint32_t aFlags)
-    : mReportedMemoryConsumption(0), mFlags(aFlags) {}
+CacheMemoryConsumer::CacheMemoryConsumer(uint32_t aFlags) {
+  StoreFlags(aFlags);
+}
 
 void CacheMemoryConsumer::DoMemoryReport(uint32_t aCurrentSize) {
-  if (!(mFlags & DONT_REPORT) && CacheStorageService::Self()) {
+  if (!(LoadFlags() & DONT_REPORT) && CacheStorageService::Self()) {
     CacheStorageService::Self()->OnMemoryConsumptionChange(this, aCurrentSize);
   }
 }
@@ -1278,13 +1279,13 @@ void CacheStorageService::OnMemoryConsumptionChange(
   LOG(("CacheStorageService::OnMemoryConsumptionChange [consumer=%p, size=%u]",
        aConsumer, aCurrentMemoryConsumption));
 
-  uint32_t savedMemorySize = aConsumer->mReportedMemoryConsumption;
+  uint32_t savedMemorySize = aConsumer->LoadReportedMemoryConsumption();
   if (savedMemorySize == aCurrentMemoryConsumption) return;
 
   // Exchange saved size with current one.
-  aConsumer->mReportedMemoryConsumption = aCurrentMemoryConsumption;
+  aConsumer->StoreReportedMemoryConsumption(aCurrentMemoryConsumption);
 
-  bool usingDisk = !(aConsumer->mFlags & CacheMemoryConsumer::MEMORY_ONLY);
+  bool usingDisk = !(aConsumer->LoadFlags() & CacheMemoryConsumer::MEMORY_ONLY);
   bool overLimit = Pool(usingDisk).OnMemoryConsumptionChange(
       savedMemorySize, aCurrentMemoryConsumption);
 
diff --git a/netwerk/cache2/CacheStorageService.h b/netwerk/cache2/CacheStorageService.h
index 107e574701bb..f9f9fafb2771 100644
--- a/netwerk/cache2/CacheStorageService.h
+++ b/netwerk/cache2/CacheStorageService.h
@@ -18,6 +18,7 @@
 #include "nsProxyRelease.h"
 #include "mozilla/Monitor.h"
 #include "mozilla/Mutex.h"
+#include "mozilla/AtomicBitfields.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/TimeStamp.h"
 #include "nsTArray.h"
@@ -43,8 +44,12 @@ class CacheEntryHandle;
 class CacheMemoryConsumer {
  private:
   friend class CacheStorageService;
-  uint32_t mReportedMemoryConsumption : 30;
-  uint32_t mFlags : 2;
+  // clang-format off
+  MOZ_ATOMIC_BITFIELDS(mAtomicBitfields, 32, (
+    (uint32_t, ReportedMemoryConsumption, 30),
+    (uint32_t, Flags, 2)
+  ))
+  // clang-format on
 
  private:
   CacheMemoryConsumer() = delete;