524d2a2812
-- Sequence Checker --
Inside a task run synchronously by RunOrPostTask,
CalledOnValidSequence() behaves like in a posted task.
-- Thread Checker --
Inside a task run synchronously by RunOrPostTask,
CalledOnValidThread() returns true iff the Thread Checker was bound
on the same thread and:
- Outside of a task [1], or,
- Inside the same task.
A Thread Checker bound inside a task run synchronously by
RunOrPostTask only returns true from CalledOnValidThread() within that
same task.
-- Implementation details --
We now lazily assign a SequenceToken to each thread. This ensures
that all bound Sequence Checkers are associated with a valid
SequenceToken (they could previously be assigned to an invalid
SequenceToken). In a scope where RunOrPostTask runs a task
synchronously, the current SequenceToken is set to the SequenceToken
captured when the SequenceManager was bound to its thread. This allows
Sequence Checker to behave the same way in a task run synchronously by
RunOrPostTask and in a posted task (even if the Sequence Checker was
bound before the SequenceManager was instantiated or bound to its
thread).
We no longer return false from CalledOnValidThread() when the Thread
Checker was bound from a different task, bound to a valid sequence
token, there is no default SingleThreadTaskRunner on the calling
thread and TLS wasn't destroyed on the calling thread. This is because
Thread Checker are now always bound to a valid SequenceToken. We rely
on a new method CurrentTaskIsThreadBound() to determine if
CalledOnValidThread() is deterministically or fortuitously called
from the bound thread.
We modified GpuWatchDogThread to use
DCHECK(task_runner()->RunsTasksInCurrentSequence()) instead of a
Sequence Checker. The GpuWatchDogThread can be stopped and started
again [2]. Previously, its Sequence Checker falled back to
PlatformThreadRef to verify sequenced execution, because it was bound
to an invalid SequenceToken. By chance, the PlatformThreadRef was
reused across restarts, so checks passed. Now that Sequence Checkers
are always bound to a valid SequenceToken, checks wouldn't pass
(SequenceToken isn't the same on the old and new threads).
[1] ThreadGroupImpl::WorkerThreadDelegateImpl::worker_thread_checker_
depends on this.
[2] https://source.chromium.org/chromium/chromium/src/+/main:content/gpu/gpu_main.cc;l=450;drc=8e78783dc1f7007bad46d657c9f332614e240fd8
Bug: 1503967
Change-Id: I295ecd716884ab97da7037ad1494d11235ce7865
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5074212
Commit-Queue: Maggie Chen <magchen@chromium.org>
Reviewed-by: Maggie Chen <magchen@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Auto-Submit: Francois Pierre Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1242801}
v8
@ 8ef649df99
Chromium
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The project's web site is https://www.chromium.org.
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Documentation in the source is rooted in docs/README.md.
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