Revert "Revert "Isolated synchronous deinit""

[ktoso]

Remove task-local tests from isolated deinit, as we don't guarantee behavior of them

This was changing back and forth during review but proposal now states that

This proposal does not define how Swift runtime should behave when
running isolated deinit. It may use task-local values as seen at the
point of the last release, reset them to default values, or use some
other set of values. Behavior is allowed to change without notice. But
future proposals may change specification by defining a specific
behavior.

and indeed we observed different behaviors failing the test. It seems we may want to drop that test entirely tbh.

[ktoso]

@swift-ci please test

[benrimmington]

The proposal hasn't been updated yet, but it was accepted with modifications:

Lastly, on the topic of task locals, the LSG agreed with reviewers who expressed that the approach of 'make no promises' was likely to result in users inadvertently relying on implementation details which would turn out to be difficult to change later, and so decided to adopt the consistent rule that task locals will always be cleared when entering an isolated deinit.

[ktoso]

Heh, my bad for assuming the proposal is up to date. Thanks for the reminder

[benrimmington]

I've created swiftlang/swift-evolution#2558 to update the proposal.

[ktoso]

Thanks, LGTM on that update.

The implementation does not match that yet actually I just remembered (and checked)...

[ktoso]

Still trying to figure out how the failures here could have ever happened... they're not possible to reproduce reliably heh.

[ktoso]

A crash we saw is

Command Output (stdout):
--
[ RUN      ] Isolated Deinit.class sync fast path
[       OK ] Isolated Deinit.class sync fast path
[ RUN      ] Isolated Deinit.class sync slow path
stdout>>> check failed at /Users/ec2-user/jenkins/workspace/oss-swift_tools-RA_stdlib-RD_test-simulator/swift/test/Concurrency/Runtime/async_task_locals_isolated_deinit.swift, line 121
stdout>>> first:  105553152229376 (of type Swift.Int)
stdout>>> second: 0 (of type Swift.Int)
stderr>>> CRASHED: SIGILL
the test crashed unexpectedly
[     FAIL ] Isolated Deinit.class sync slow path
[ RUN      ] Isolated Deinit.actor sync fast path
[       OK ] Isolated Deinit.actor sync fast path
[ RUN      ] Isolated Deinit.actor sync slow path
[       OK ] Isolated Deinit.actor sync slow path
[ RUN      ] Isolated Deinit.no TLs
[       OK ] Isolated Deinit.no TLs
Isolated Deinit: Some tests failed, aborting
UXPASS: []
FAIL: ["class sync slow path"]
SKIP: []
To debug, run:
$ /Users/ec2-user/jenkins/workspace/oss-swift_tools-RA_stdlib-RD_test-simulator/build/Ninja-ReleaseAssert/swift-macosx-x86_64/test-macosx-x86_64/Concurrency/Runtime/Output/async_task_locals_isolated_deinit.swift.tmp/a.out --stdlib-unittest-in-process --stdlib-unittest-filter "class sync slow path"

showing a corrupted value on self -- the task local value is properly 0 as expected though...

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please test

[ktoso]

@swift-ci please smoke test macOS

[ktoso]

@swift-ci please smoke test macOS

[ktoso]

@swift-ci please test macOS

[ktoso]

@swift-ci please test macOS