Revert "Implement base::GetContinuationTaskRunner()."
This reverts commit 0dd49956177733fd57fa1698e357ee83f6074494.
Reason for revert:
Remove the ability to get the current task runner according to
the recent discussions in scheduler-dev@ [1].
[1] https://docs.google.com/document/d/1tssusPykvx3g0gvbvU4HxGyn3MjJlIylnsH13-Tv6s4/edit
[email protected],[email protected],[email protected]
BUG=1026641
Original change's description:
> Implement base::GetContinuationTaskRunner().
>
> This returns to the current task's task runner. Note there are some
> situations where this is not valid:
>
> * When we're not running a task (it will DCHECK).
> * When we're in a one-off base::ThreadPool task (it will DCHECK).
> * In non-scheduler backed threads (it will DCHECK).
>
> Bug: 835323
> Change-Id: I3a789557247240e0c36a47339574350d79746144
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1834094
> Commit-Queue: Gabriel Charette <[email protected]>
> Reviewed-by: Gabriel Charette <[email protected]>
> Reviewed-by: Rohit Rao <[email protected]>
> Reviewed-by: François Doray <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#707484}
[email protected],[email protected],[email protected],[email protected]
# Not skipping CQ checks because original CL landed > 1 day ago.
Bug: 835323
Change-Id: I233ff3ba4e2f20e23a67a3bf6c46734608144eca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1959917
Reviewed-by: Alexander Timin <[email protected]>
Reviewed-by: Gabriel Charette <[email protected]>
Commit-Queue: Alexander Timin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#728982}
diff --git a/docs/threading_and_tasks.md b/docs/threading_and_tasks.md
index bb1a725..5a705c2c 100644
--- a/docs/threading_and_tasks.md
+++ b/docs/threading_and_tasks.md
@@ -376,6 +376,28 @@
threads](#prefer-sequences-to-physical-threads) and that this thus should rarely
be necessary.
+### Posting to the Current Thread
+
+*** note
+**IMPORTANT:** To post a task that needs mutual exclusion with the current
+sequence of tasks but doesn’t absolutely need to run on the current physical thread,
+use `base::SequencedTaskRunnerHandle::Get()` instead of
+`base::ThreadTaskRunnerHandle::Get()` (ref. [Posting to the Current
+Sequence](#Posting-to-the-Current-Virtual_Thread)). That will better document the
+requirements of the posted task and will avoid unnecessarily making your API
+physical thread-affine. In a single-thread task, `base::SequencedTaskRunnerHandle::Get()`
+is equivalent to `base::ThreadTaskRunnerHandle::Get()`.
+***
+
+If you must post a task to the current physical thread nonetheless, use
+[`base::ThreadTaskRunnerHandle`](https://cs.chromium.org/chromium/src/base/threading/thread_task_runner_handle.h).
+
+```cpp
+// The task will run on the current thread in the future.
+base::ThreadTaskRunnerHandle::Get()->PostTask(
+ FROM_HERE, base::BindOnce(&Task));
+```
+
## Posting Tasks to a COM Single-Thread Apartment (STA) Thread (Windows)
Tasks that need to run on a COM Single-Thread Apartment (STA) thread must be
