Bug 126215 – Replace WTF::ThreadingOnce with std::call_once

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Anders Carlsson]

Replace WTF::ThreadingOnce with std::call_once

[Anders Carlsson]

Created attachment 219977 [details]
Patch

[WebKit Commit Bot]

Attachment 219977 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/JavaScriptCore/ChangeLog', u'Source/JavaScriptCore/dfg/DFGWorklist.cpp', u'Source/JavaScriptCore/runtime/InitializeThreading.cpp', u'Source/WTF/ChangeLog', u'Source/WTF/GNUmakefile.list.am', u'Source/WTF/wtf/CompilationThread.cpp', u'Source/WTF/wtf/ThreadingOnce.h', '--commit-queue']" exit_code: 1
ERROR: Source/JavaScriptCore/runtime/InitializeThreading.cpp:55:  Missing space before {  [whitespace/braces] [5]
ERROR: Source/WTF/wtf/CompilationThread.cpp:41:  Missing space before {  [whitespace/braces] [5]
Total errors found: 2 in 5 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Sam Weinig]

Not that it matters in these places much, but how does the performance of std::call_once compare to pthread_once and dispatch_once? I see in libc++'s implementation there is comment stating it should consider moving to dispatch_once (presumably for performance reasons) http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/mutex.cpp?view=markup#l209.  The comment seems predicated on dispatch_once_f supporting c++ exceptions, but perhaps the maintainers would consider an optimized version when exceptions were disabled as they are with WebKit.

[Anders Carlsson]

(In reply to comment #3)
> Not that it matters in these places much, but how does the performance of std::call_once compare to pthread_once and dispatch_once?

It's faster than pthread_once since the first check ends up being inlined.

[WebKit Commit Bot]

Comment on attachment 219977 [details]
Patch

Clearing flags on attachment: 219977

Committed r161146: <http://trac.webkit.org/changeset/161146>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.