Avoid data race on CrossThreadPersistents during thread detachment.

Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=haraken
BUG=584250
Committed: https://crrev.com/09e769ad8f46553a3833223269c8b5d43db60199
Cr-Commit-Position: refs/heads/master@{#373814}

[sof, 2016-02-05 10:50:24]

sigbjornf@opera.com changed reviewers:
+ oilpan-reviews@chromium.org

[sof, 2016-02-05 10:50:24]

please take a look.

This touches on crbug.com/515432 , and a shorter-term fix until per-thread heaps
have landed?

[haraken, 2016-02-05 11:02:21]

LGTM

[sof, 2016-02-05 15:22:37]

Description was changed from

==========
Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=
BUG=584250
==========

to

==========
Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=haraken
BUG=584250
==========

[sof, 2016-02-05 15:23:43]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2016-02-05 15:24:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1670813004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1670813004/1

[commit-bot: I haz the power, 2016-02-05 15:29:29]

Description was changed from

==========
Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=haraken
BUG=584250
==========

to

==========
Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=haraken
BUG=584250
==========

[commit-bot: I haz the power, 2016-02-05 15:29:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-05 15:30:05]

Description was changed from

==========
Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=haraken
BUG=584250
==========

to

==========
Avoid data race on CrossThreadPersistents during thread detachment.

As part of detaching a thread from Oilpan and emptying its heap, the
CrossThreadPersistent<>s pointing into that heap are cleared. Doing
so entails traversing the collection of such persistents and checking
their heap membership -- that traversal might race with other threads
who are not at any safepoint.

To avoid the race, insist that updates to CrossThreadPersistent<>s are
atomic along with the corresponding read when doing the above
traversal.

R=haraken
BUG=584250

Committed: https://crrev.com/09e769ad8f46553a3833223269c8b5d43db60199
Cr-Commit-Position: refs/heads/master@{#373814}
==========

[commit-bot: I haz the power, 2016-02-05 15:30:06]

Patchset 1 (id:??) landed as
https://crrev.com/09e769ad8f46553a3833223269c8b5d43db60199
Cr-Commit-Position: refs/heads/master@{#373814}