wtf/Atomics.h: Remove Android/ARM kernel helpers.

wtf/Atomics.h: Remove Android/ARM kernel helpers.

Future Android kernels are going to remove the special
page that is mapped in every process at a fixed address,
and which provides optimized low-level operations.

Instead of calling the memory helper related to memory
barriers, use __sync_synchonize which will generate a
DMB instruction directly, just like all other
platforms (e.g. Linux/ARM).

The only benefit of using the kernel helper was to avoid
the DMB instruction on single-core devices, which are
now totally obsolete.

This change only impacts Android/ARM builds.

BUG=686001
Review-Url: https://codereview.chromium.org/2651203006
Cr-Commit-Position: refs/heads/master@{#447008}
Committed: https://chromium.googlesource.com/chromium/src/+/70847b53c7d1d5d8c65d526f966718a9e2c8adef

[digit1, 2017-01-27 17:39:25]

The CQ bit was checked by digit@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-01-27 17:39:58]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-27 21:27:09]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-01-27 21:27:10]

Dry run: This issue passed the CQ dry run.

[digit1, 2017-01-30 15:12:45]

Description was changed from

==========
wtf/Atomics.h: Remove Android/ARM kernel helpers.

Future Android kernels are going to remove the special
page that is mapped in every process at a fixed address,
and which provides optimized low-level operations.

Instead of calling the memory helper related to memory
barriers, use __sync_synchonize which will generate a
DMB instruction directly, just like all other
platforms (e.g. Linux/ARM).

The only benefit of use the kernel helper was to avoid
the DMB instruction on single-core devices, which are
now totally obsolete.

This change only impacts Android/ARM builds.

BUG=686001
==========

to

==========
wtf/Atomics.h: Remove Android/ARM kernel helpers.

Future Android kernels are going to remove the special
page that is mapped in every process at a fixed address,
and which provides optimized low-level operations.

Instead of calling the memory helper related to memory
barriers, use __sync_synchonize which will generate a
DMB instruction directly, just like all other
platforms (e.g. Linux/ARM).

The only benefit of using the kernel helper was to avoid
the DMB instruction on single-core devices, which are
now totally obsolete.

This change only impacts Android/ARM builds.

BUG=686001
==========

[digit1, 2017-01-30 15:15:16]

digit@chromium.org changed reviewers:
+ haraken@chromium.org

[digit1, 2017-01-30 15:15:17]

Hello haraken@, please review this change in wtf/Atomics.h

[haraken, 2017-01-30 15:21:42]

LGTM

[digit1, 2017-01-30 15:26:25]

The CQ bit was checked by digit@chromium.org

[commit-bot: I haz the power, 2017-01-30 15:26:47]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-30 17:41:12]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1485789985802040, "parent_rev":
"081204fd1fa37581d7b8a8b7cc7e13d83e0919a3", "commit_rev":
"70847b53c7d1d5d8c65d526f966718a9e2c8adef"}

[commit-bot: I haz the power, 2017-01-30 17:41:44]

Description was changed from

==========
wtf/Atomics.h: Remove Android/ARM kernel helpers.

Future Android kernels are going to remove the special
page that is mapped in every process at a fixed address,
and which provides optimized low-level operations.

Instead of calling the memory helper related to memory
barriers, use __sync_synchonize which will generate a
DMB instruction directly, just like all other
platforms (e.g. Linux/ARM).

The only benefit of using the kernel helper was to avoid
the DMB instruction on single-core devices, which are
now totally obsolete.

This change only impacts Android/ARM builds.

BUG=686001
==========

to

==========
wtf/Atomics.h: Remove Android/ARM kernel helpers.

Future Android kernels are going to remove the special
page that is mapped in every process at a fixed address,
and which provides optimized low-level operations.

Instead of calling the memory helper related to memory
barriers, use __sync_synchonize which will generate a
DMB instruction directly, just like all other
platforms (e.g. Linux/ARM).

The only benefit of using the kernel helper was to avoid
the DMB instruction on single-core devices, which are
now totally obsolete.

This change only impacts Android/ARM builds.

BUG=686001

Review-Url: https://codereview.chromium.org/2651203006
Cr-Commit-Position: refs/heads/master@{#447008}
Committed:
https://chromium.googlesource.com/chromium/src/+/70847b53c7d1d5d8c65d526f9667...
==========

[commit-bot: I haz the power, 2017-01-30 17:41:45]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/70847b53c7d1d5d8c65d526f9667...