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| author | glider@chromium.org <glider@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98> | 2014-03-07 08:51:32 +0000 |
|---|---|---|
| committer | glider@chromium.org <glider@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98> | 2014-03-07 08:51:32 +0000 |
| commit | 6e646e9404107153ab3930c924a1d752733a859c (patch) | |
| tree | 4673d9c23c1d978d84f345db908a70f643bfc9ba /base/memory | |
| parent | 8857d54b061e603d7c323106279f6cfafe9e1a8a (diff) | |
| download | chromium_src-6e646e9404107153ab3930c924a1d752733a859c.zip chromium_src-6e646e9404107153ab3930c924a1d752733a859c.tar.gz chromium_src-6e646e9404107153ab3930c924a1d752733a859c.tar.bz2 | |
Fix base::internal::Singleton to use acquire loads instead of nobarrier ones.
The NoBarrier_Load operations don't actually guarantee that the singleton data
associated with the pointer is visible to the thread calling get() even if the
pointer is initialized.
R=mark@chromium.org, dvyukov@chromium.org, epenner@chromium.org
Review URL: https://codereview.chromium.org/188603002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255552 0039d316-1c4b-4281-b951-d872f2087c98
Diffstat (limited to 'base/memory')
| -rw-r--r-- | base/memory/singleton.cc | 5 | ||||
| -rw-r--r-- | base/memory/singleton.h | 5 |
2 files changed, 8 insertions, 2 deletions
diff --git a/base/memory/singleton.cc b/base/memory/singleton.cc index ee5e58d..f68ecaa 100644 --- a/base/memory/singleton.cc +++ b/base/memory/singleton.cc @@ -18,7 +18,10 @@ subtle::AtomicWord WaitForInstance(subtle::AtomicWord* instance) { // the object has been created. subtle::AtomicWord value; while (true) { - value = subtle::NoBarrier_Load(instance); + // The load has acquire memory ordering as the thread which reads the + // instance pointer must acquire visibility over the associated data. + // The pairing Release_Store operation is in Singleton::get(). + value = subtle::Acquire_Load(instance); if (value != kBeingCreatedMarker) break; PlatformThread::YieldCurrentThread(); diff --git a/base/memory/singleton.h b/base/memory/singleton.h index 355aad0..e5e2e3e 100644 --- a/base/memory/singleton.h +++ b/base/memory/singleton.h @@ -233,7 +233,9 @@ class Singleton { base::ThreadRestrictions::AssertSingletonAllowed(); #endif - base::subtle::AtomicWord value = base::subtle::NoBarrier_Load(&instance_); + // The load has acquire memory ordering as the thread which reads the + // instance_ pointer must acquire visibility over the singleton data. + base::subtle::AtomicWord value = base::subtle::Acquire_Load(&instance_); if (value != 0 && value != base::internal::kBeingCreatedMarker) { // See the corresponding HAPPENS_BEFORE below. ANNOTATE_HAPPENS_AFTER(&instance_); @@ -252,6 +254,7 @@ class Singleton { // synchronization between different threads calling get(). // See the corresponding HAPPENS_AFTER below and above. ANNOTATE_HAPPENS_BEFORE(&instance_); + // Releases the visibility over instance_ to the readers. base::subtle::Release_Store( &instance_, reinterpret_cast<base::subtle::AtomicWord>(newval)); |