Bug 131630

Summary:

monotonicallyIncreasingTime() should only initialize its static timebaseInfo once

Product:

WebKit

Reporter:

Mark Lam <mark.lam>

Component:

JavaScriptCore

Assignee:

Mark Lam <mark.lam>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

benjamin, cmarcelo, commit-queue, fpizlo, ggaren, mhahnenberg, mmirman, msaboff, oliver, simon.fraser

Priority:

Keywords:

InRadar

Version:

528+ (Nightly build)

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
the patch	fpizlo: review+

Description Mark Lam 2014-04-14 12:51:58 PDT

The current initialization of the static field is not thread safe.

Comment 1 Mark Lam 2014-04-14 12:52:54 PDT

<rdar://problem/16413527>

Comment 2 Mark Lam 2014-04-14 13:02:53 PDT

Created attachment 229302 [details]
the patch

Comment 3 Filip Pizlo 2014-04-14 13:20:28 PDT

Comment on attachment 229302 [details]
the patch

View in context: https://bugs.webkit.org/attachment.cgi?id=229302&action=review

> Source/WTF/wtf/CurrentTime.cpp:278
>      // Based on listing #2 from Apple QA 1398.
>      static mach_timebase_info_data_t timebaseInfo;
> -    if (!timebaseInfo.denom) {
> +    static std::once_flag initializeTimerOnceFlag;
> +    std::call_once(initializeTimerOnceFlag, [] {

You should change the comment to say that it fixes the race condition in that listing.  Say something like "Based on listing #2 from Apple QA 1398, but modified to be thread-safe".

Comment 4 Mark Lam 2014-04-14 13:33:06 PDT

Thanks.  Patch has been updated as suggested.  Landed in r167263: <http://trac.webkit.org/r167263>.