SkTRacy<T> -> SkAtomic<T>

SkTRacy<T> -> SkAtomic<T>

Like SkTRacy<T>, TSAN will not complain about these.  Unlike SkTRacy<T>, TSAN
should not complain about these: SkAtomic<T> are threadsafe.

This should fix the races now suppressed in TSAN.  As written, the memory
barriers we're using in SkPixelRef will be dumb but safe (really, dumbest
possible but safest possible).  If we see a perf hit, we can follow up by
putting Ben and I in a room for a while, thinking about it really hard, and
using the minimum-strength safe memory barriers.

A refactor that steals a bit from the genID would also still be possible with
this approach.

BUG=chromium:437511
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu13.10-GCE-NoGPU-x86_64-Release-TSAN-Trybot

Committed: https://skia.googlesource.com/skia/+/86821b56704ebc0a1a6d1e5d1e329369ac797c98

[mtklein_C, 2015-02-24 22:18:55]

mtklein@chromium.org changed reviewers:
+ reed@google.com

[reed2, 2015-02-24 22:21:39]

reed@chromium.org changed reviewers:
+ bungeman@google.com, reed@chromium.org

[reed2, 2015-02-24 22:21:40]

lgtm

[mtklein, 2015-02-24 22:26:54]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-02-24 22:27:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/955803002/40001

[commit-bot: I haz the power, 2015-02-24 22:28:45]

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

[commit-bot: I haz the power, 2015-02-24 22:28:46]

Try jobs failed on following builders:
  Build-Ubuntu13.10-Clang-x86_64-Debug-Trybot on client.skia.compile
(JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu13.10-Cl...)

[mtklein, 2015-02-24 22:30:47]

The CQ bit was checked by mtklein@google.com

[mtklein, 2015-02-24 22:30:47]

The patchset sent to the CQ was uploaded after l-g-t-m from reed@chromium.org
Link to the patchset: https://codereview.chromium.org/955803002/#ps60001 (title:
"great warning")

[commit-bot: I haz the power, 2015-02-24 22:31:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/955803002/60001

[commit-bot: I haz the power, 2015-02-24 22:38:17]

Committed patchset #4 (id:60001) as
https://skia.googlesource.com/skia/+/86821b56704ebc0a1a6d1e5d1e329369ac797c98

[Alexander Potapenko, 2015-03-10 09:55:19]

glider@chromium.org changed reviewers:
+ glider@chromium.org

[Alexander Potapenko, 2015-03-10 09:55:20]

https://codereview.chromium.org/955803002/diff/60001/src/core/SkPixelRef.cpp
File src/core/SkPixelRef.cpp (right):

https://codereview.chromium.org/955803002/diff/60001/src/core/SkPixelRef.cpp#...
src/core/SkPixelRef.cpp:125: fGenerationID.store(0);
Perhaps the sk_memory_order_acquire and sk_memory_order_release should be enough
here.
Agreed this isn't necessary if the performance impact is minor.

[mtklein, 2015-03-10 13:33:12]

https://codereview.chromium.org/955803002/diff/60001/src/core/SkPixelRef.cpp
File src/core/SkPixelRef.cpp (right):

https://codereview.chromium.org/955803002/diff/60001/src/core/SkPixelRef.cpp#...
src/core/SkPixelRef.cpp:125: fGenerationID.store(0);
On 2015/03/10 09:55:20, Alexander Potapenko wrote:
> Perhaps the sk_memory_order_acquire and sk_memory_order_release should be
enough
> here.
> Agreed this isn't necessary if the performance impact is minor.

Yep, I think acquire-release is enough too.  So far this hasn't seemed hot
enough to worry yet, but we'll keep it in mind.  Thanks for thinking about it!