code review 7913043: runtime: prevent garbage collection during hashmap insertion

runtime: prevent garbage collection during hashmap insertion

Inserting a key-value pair into a hashmap storing keys or values
indirectly can cause the garbage collector to find the hashmap in
an inconsistent	state.

Fixes issue 5074.

[atom, 2013-03-19 20:05:05]

Hello golang-dev@googlegroups.com (cc: dave@cheney.net),

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

[minux1, 2013-03-19 20:14:01]

code looks reasonable, could we make a test for it?
is channel affected by this issue?

[ugorji, 2013-03-19 20:23:17]

On 2013/03/19 20:05:05, atom wrote:
> Hello mailto:golang-dev@googlegroups.com (cc: mailto:dave@cheney.net),
> 
> I'd like you to review this change to
> https://code.google.com/p/go/

Tested a few times. My benchmark finishes now without errors. I think this fixes
the issue.

[atom, 2013-03-19 20:26:53]

On 2013/03/19 20:14:01, minux wrote:
> is channel affected by this issue?

Probably not.

[rsc, 2013-03-19 20:29:37]

LGTM

[atom, 2013-03-19 20:53:55]

Hello golang-dev@googlegroups.com, minux.ma@gmail.com, ugorji@gmail.com,
rsc@golang.org (cc: dave@cheney.net, golang-dev@googlegroups.com),

Please take another look.

[rsc, 2013-03-19 20:57:39]

LGTM

https://codereview.appspot.com/7913043/diff/10001/src/pkg/runtime/gc_test.go
File src/pkg/runtime/gc_test.go (right):

https://codereview.appspot.com/7913043/diff/10001/src/pkg/runtime/gc_test.go#...
src/pkg/runtime/gc_test.go:87: type T struct {
you might try 

defer debug.SetGCPercent(debug.SetGCPercent(1))

to try to make the collector run a lot during the test.

[atom, 2013-03-19 21:16:56]

https://codereview.appspot.com/7913043/diff/10001/src/pkg/runtime/gc_test.go
File src/pkg/runtime/gc_test.go (right):

https://codereview.appspot.com/7913043/diff/10001/src/pkg/runtime/gc_test.go#...
src/pkg/runtime/gc_test.go:87: type T struct {
On 2013/03/19 20:57:40, rsc wrote:
> you might try 
> 
> defer debug.SetGCPercent(debug.SetGCPercent(1))
> 
> to try to make the collector run a lot during the test.

Done.

[atom, 2013-03-19 21:17:55]

*** Submitted as https://code.google.com/p/go/source/detail?r=53c873e9f93d ***

runtime: prevent garbage collection during hashmap insertion

Inserting a key-value pair into a hashmap storing keys or values
indirectly can cause the garbage collector to find the hashmap in
an inconsistent	state.

Fixes issue 5074.

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/7913043