rt: cleanup and simplify scheduler (scheduler v2.5) #2273
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A refactor of the scheduler internals focusing on simplifying and reducing unsafety. There are no fundamental logic changes. * The state transitions of the core task component are refined and reduced. * `basic_scheduler` has all unsafety removed. * `local_set` has most unsafety removed. * `threaded_scheduler` limits unsafety to its queue implementation.
carllerche
changed the title
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cc @tmiasko, this is the cleanup I mentioned before. If you can help w/ CI configuration, I would be happy to set this up w/ TSAN as long as we can remove false positives. You mentioned you had a strategy to do so? |
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And I only ran with MAX_PREEMPTIONS=1 locally before the final push because it takes too long 😢 |
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Regarding the thread sanitizer, the first step would be to remove the uses of # Install the source code of the standard library.
$ rustup component add rust-src
# Replace fences with atomic loads in Arc implementation.
$ patch ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/liballoc/sync.rs <<EOF
405c405
< atomic::fence(Acquire);
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> this.inner().strong.load(Acquire);
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< atomic::fence(Acquire);
---
> self.inner().weak.load(Acquire);
1246c1246
< atomic::fence(Acquire);
---
> self.inner().strong.load(Acquire);
1704c1704
< atomic::fence(Acquire);
---
> inner.weak.load(Acquire);
EOF
# Enable thread sanitizer.
$ export RUSTFLAGS=-Zsanitizer=thread RUSTDOCFLAGS=-Zsanitizer=thread
# Run tests with instrumented standard library.
$ cargo -Zbuild-std test --workspace --target x86_64-unknown-linux-gnuBTW. Looks like there is a data race on the scheduler field, since task is |
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@tmiasko Yes re: race. I failed to run the full suite locally before pushing after making a tweak... working on a fix now. |
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| /// Create a new local run-queue | ||
| pub(super) fn local<T: 'static>() -> (Steal<T>, Local<T>) { | ||
| debug_assert!(LOCAL_QUEUE_CAPACITY >= 2 && LOCAL_QUEUE_CAPACITY.is_power_of_two()); |
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Is there a way for us to make this a static assertion instead?
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do you have thoughts on how?
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Seems like hax 😆 you want me to lift that macro?
| /// requires ensuring mutal exclusion between any concurrent thread that | ||
| /// might modify the future or output field. | ||
| /// | ||
| /// The mutual exclusion is implemented by `Harness` and the `Lifecycle` |
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nit: do we still call this lifecycle, or is it called stage now?
Co-Authored-By: Eliza Weisman <eliza@buoyant.io>
Co-Authored-By: Eliza Weisman <eliza@buoyant.io>
rt: cleanup and simplify scheduler (scheduler v2.5) (tokio-rs#2273)
A refactor of the scheduler internals focusing on simplifying and
reducing unsafety. There are no fundamental logic changes. That said,
I recommend reading the new files themselves and not the diff.
reduced.
basic_schedulerhas (almost) all unsafety removed.local_sethas most unsafety removed.threaded_schedulerlimits unsafety to its queue implementation.