Magic-Mirror/gecko-dev
1
0
Fork 0
mirror of https://github.com/mozilla/gecko-dev.git synced 2024-10-08 19:04:45 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Bug 1627572 - Use an atomic bool for a quick-return check in FilePreferences::IsAllowedPath, r=michal

Browse Source 
Differential Revision: https://phabricator.services.mozilla.com/D69976

--HG--
extra : moz-landing-system : lando
This commit is contained in:
Honza Bambas 2020-04-07 11:18:54 +00:00
parent 96206c08cb
commit aa4bbee2f9
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
xpcom/io/FilePreferences.cpp
View File

@ -6,6 +6,7 @@
#include "FilePreferences.h"
#include "mozilla/Atomics.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/Preferences.h"
#include "mozilla/StaticMutex.h"
@ -37,8 +38,11 @@ typedef char16_t char_path_t;
typedef char char_path_t;
#endif
// Initially false to make concurrent consumers acquire the lock and sync
// Initially false to make concurrent consumers acquire the lock and sync.
// The plain bool is synchronized with sMutex, the atomic one is for a quick
// check w/o the need to acquire the lock on the hot path.
static bool sBlacklistEmpty = false;
static Atomic<bool, Relaxed> sBlacklistEmptyQuickCheck{false};
typedef nsTArray<nsTString<char_path_t>> Paths;
static StaticAutoPtr<Paths> sBlacklist;
@ -92,7 +96,7 @@ void InitPrefs() {
StaticMutexAutoLock lock(sMutex);
if (blacklist.IsEmpty()) {
sBlacklistEmpty = true;
sBlacklistEmptyQuickCheck = (sBlacklistEmpty = true);
return;
}
@ -108,7 +112,7 @@ void InitPrefs() {
Unused << p.CheckChar(',');
}
sBlacklistEmpty = PathBlacklist().Length() == 0;
sBlacklistEmptyQuickCheck = (sBlacklistEmpty = PathBlacklist().Length() == 0);
}
void InitDirectoriesWhitelist() {
@ -268,14 +272,13 @@ const char kPathSeparator = '/';
bool IsAllowedPath(const nsTSubstring<char_path_t>& aFilePath) {
typedef TNormalizer<char_path_t> Normalizer;
// A quick check out of the lock.
if (sBlacklistEmpty) {
// An atomic quick check out of the lock, because this is mostly `true`.
if (sBlacklistEmptyQuickCheck) {
return true;
}
StaticMutexAutoLock lock(sMutex);
// Recheck the flag under the lock to reload it.
if (sBlacklistEmpty) {
return true;
}