Bug 1607224 - Data race on CacheFileHandle::mFileSize r=valentin

This patch fixes data race on CacheFileHandle::mFileSize when accessed on main thread by nsHttpChannel::ReportNetVSCacheTelemetry(). All other usages are on cache I/O thread.

Differential Revision: https://phabricator.services.mozilla.com/D60407

--HG--
extra : moz-landing-system : lando

netwerk/cache2/CacheFileIOManager.cpp

@@ -178,7 +178,7 @@ void CacheFileHandle::Log() {
          "pinning=%" PRIu32 ", fileExists=%d, fileSize=%" PRId64
          ", leafName=%s, key=%s]",
          this, bool(mIsDoomed), bool(mPriority), bool(mClosed), bool(mInvalid),
-         static_cast<uint32_t>(mPinning), bool(mFileExists), mFileSize,
+         static_cast<uint32_t>(mPinning), bool(mFileExists), int64_t(mFileSize),
          leafName.get(), mKey.get()));
   } else {
     LOG(
@@ -189,7 +189,7 @@ void CacheFileHandle::Log() {
          ", leafName=%s, key=%s]",
          this, LOGSHA1(mHash), bool(mIsDoomed), bool(mPriority), bool(mClosed),
          bool(mInvalid), static_cast<uint32_t>(mPinning), bool(mFileExists),
-         mFileSize, leafName.get(), mKey.get()));
+         int64_t(mFileSize), leafName.get(), mKey.get()));
   }
 }
 
@@ -1637,9 +1637,11 @@ nsresult CacheFileIOManager::OpenFileInternal(const SHA1Sum::Hash* aHash,
       MOZ_ASSERT(!handle->IsDoomed() && NS_SUCCEEDED(rv));
     }
 
-    rv = file->GetFileSize(&handle->mFileSize);
+    int64_t fileSize = -1;
+    rv = file->GetFileSize(&fileSize);
     NS_ENSURE_SUCCESS(rv, rv);
 
+    handle->mFileSize = fileSize;
     handle->mFileExists = true;
 
     CacheIndex::EnsureEntryExists(aHash);
@@ -1735,9 +1737,11 @@ nsresult CacheFileIOManager::OpenSpecialFileInternal(
   mSpecialHandles.AppendElement(handle);
 
   if (exists) {
-    rv = file->GetFileSize(&handle->mFileSize);
+    int64_t fileSize = -1;
+    rv = file->GetFileSize(&fileSize);
     NS_ENSURE_SUCCESS(rv, rv);
 
+    handle->mFileSize = fileSize;
     handle->mFileExists = true;
   } else {
     handle->mFileSize = 0;

netwerk/cache2/CacheFileIOManager.h

@@ -122,7 +122,10 @@ class CacheFileHandle final : public nsISupports {
   PinningStatus mPinning;
 
   nsCOMPtr<nsIFile> mFile;
-  int64_t mFileSize;
+
+  // file size is atomic because it is used on main thread by
+  // nsHttpChannel::ReportNetVSCacheTelemetry()
+  Atomic<int64_t, Relaxed> mFileSize;
   PRFileDesc* mFD;  // if null then the file doesn't exists on the disk
   nsCString mKey;
 };