code review 11454044: runtime: prevent GC from seeing the contents of a frame...

runtime: prevent GC from seeing the contents of a frame in runfinq
This holds the last finalized object and arguments to its finalizer.
Fixes issue 5348.

[dvyukov, 2013-07-19 11:53:08]

Hello golang-dev@googlegroups.com,

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

[iant, 2013-07-19 13:21:18]

https://codereview.appspot.com/11454044/diff/6001/src/pkg/runtime/mgc0.c
File src/pkg/runtime/mgc0.c (right):

https://codereview.appspot.com/11454044/diff/6001/src/pkg/runtime/mgc0.c#newc...
src/pkg/runtime/mgc0.c:2277: frame = runtime·mallocgc(framesz, FlagNoPointers,
0, 1);
I think this needs a comment.

[dvyukov, 2013-07-19 13:47:15]

On 2013/07/19 13:21:18, iant wrote:
> https://codereview.appspot.com/11454044/diff/6001/src/pkg/runtime/mgc0.c
> File src/pkg/runtime/mgc0.c (right):
> 
>
https://codereview.appspot.com/11454044/diff/6001/src/pkg/runtime/mgc0.c#newc...
> src/pkg/runtime/mgc0.c:2277: frame = runtime·mallocgc(framesz, FlagNoPointers,
> 0, 1);
> I think this needs a comment.

Done
PTAL

[iant, 2013-07-19 13:52:50]

LGTM

https://codereview.appspot.com/11454044/diff/12001/src/pkg/runtime/mgc0.c
File src/pkg/runtime/mgc0.c (right):

https://codereview.appspot.com/11454044/diff/12001/src/pkg/runtime/mgc0.c#new...
src/pkg/runtime/mgc0.c:2277: // The frame does not contain interesting for GC
pointers,
s/interesting for GC pointers/pointers interesting for GC/

https://codereview.appspot.com/11454044/diff/12001/src/pkg/runtime/mgc0.c#new...
src/pkg/runtime/mgc0.c:2278: // all not yet finalized objects are stored in
finc.
s/finc/finq/

[dvyukov, 2013-07-19 14:00:42]

https://codereview.appspot.com/11454044/diff/12001/src/pkg/runtime/mgc0.c
File src/pkg/runtime/mgc0.c (right):

https://codereview.appspot.com/11454044/diff/12001/src/pkg/runtime/mgc0.c#new...
src/pkg/runtime/mgc0.c:2277: // The frame does not contain interesting for GC
pointers,
On 2013/07/19 13:52:50, iant wrote:
> s/interesting for GC pointers/pointers interesting for GC/

Done.

https://codereview.appspot.com/11454044/diff/12001/src/pkg/runtime/mgc0.c#new...
src/pkg/runtime/mgc0.c:2278: // all not yet finalized objects are stored in
finc.
On 2013/07/19 13:52:50, iant wrote:
> s/finc/finq/

It's finc.

Once runfinq() grabs all current objects from finq:
fb = finq;
finq = nil;

finq does not contain then anymore, but they are still not finalized and so
reachable.
GC scans finc.

This makes the whole batch unavailable for GC:
fb->cnt = 0;

[dvyukov, 2013-07-19 14:01:37]

*** Submitted as https://code.google.com/p/go/source/detail?r=548d6782f20e ***

runtime: prevent GC from seeing the contents of a frame in runfinq
This holds the last finalized object and arguments to its finalizer.
Fixes issue 5348.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/11454044