code review 126870043: runtime: fix data race in stackalloc

runtime: fix data race in stackalloc
Stack shrinking happens during mark phase,
and it assumes that it owns stackcache in mcache.
Stack cache flushing also happens during mark phase,
and it accesses stackcache's w/o any synchronization.
This leads to stackcache corruption:
http://goperfd.appspot.com/log/309af5571dfd7e1817259b9c9cf9bcf9b2c27610

[dvyukov, 2014-08-08 15:27:18]

Hello khr@golang.org (cc: golang-codereviews@googlegroups.com, rsc@golang.org),

I'd like you to review this change to
https://dvyukov%40google.com@code.google.com/p/go/

[khr, 2014-08-08 15:31:46]

On 2014/08/08 15:27:18, dvyukov wrote:
> Hello mailto:khr@golang.org (cc: mailto:golang-codereviews@googlegroups.com,
mailto:rsc@golang.org),
> 
> I'd like you to review this change to
> https://dvyukov%40google.com@code.google.com/p/go/

LGTM.

[dvyukov, 2014-08-08 16:14:06]

*** Submitted as https://code.google.com/p/go/source/detail?r=e9af2ad43c07 ***

runtime: fix data race in stackalloc
Stack shrinking happens during mark phase,
and it assumes that it owns stackcache in mcache.
Stack cache flushing also happens during mark phase,
and it accesses stackcache's w/o any synchronization.
This leads to stackcache corruption:
http://goperfd.appspot.com/log/309af5571dfd7e1817259b9c9cf9bcf9b2c27610

LGTM=khr
R=khr
CC=golang-codereviews, rsc
https://codereview.appspot.com/126870043

[rsc, 2014-08-08 20:45:07]

nice, this fixed amd64p32