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epoch: Fix stacked borrows violations #871

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@taiki-e taiki-e commented Jul 20, 2022 •
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Fixes #545

See #545 (comment) for the reported stacked borrows violations.

Note: this is a breaking change because changes API of Pointable trait

@taiki-e taiki-e marked this pull request as draft July 20, 2022 02:00
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from fcafef5 to 8e29940 Compare July 20, 2022 16:30
@taiki-e taiki-e marked this pull request as ready for review July 21, 2022 01:20
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch 3 times, most recently from f25a4cd to a81e099 Compare July 22, 2022 15:24
@taiki-e taiki-e mentioned this pull request Jul 22, 2022
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@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from e7c8fbf to 86c1680 Compare July 22, 2022 18:14
bors bot added a commit that referenced this pull request Jul 23, 2022
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Merge #796 #881
e733110 
796: epoch: Remove ptr-to-int casts r=taiki-e a=taiki-e

Use [this hack](rust-lang/miri#1866 (comment)) to fix compatibility issues with Miri (see #490 (comment) for details). 

Due to the #545, still not compatible with stacked borrows. This will be fixed by the subsequent PR (#871).

Note: this is a breaking change because changes API of Pointable and Pointer traits

Fixes #579

881: Remove deprecated items r=taiki-e a=taiki-e

This removes the following deprecated items:

- crossbeam-epoch:
  - `CompareAndSetError`
  - `CompareAndSetOrdering`
  - `Atomic::compare_and_set`
  - `Atomic::compare_and_set_weak`
- crossbeam-utils:
  - `AtomicCell::compare_and_swap`

Co-authored-by: Taiki Endo <te316e89@gmail.com>
bors bot added a commit that referenced this pull request Jul 23, 2022
@bors @taiki-e
Merge #796
0fbc9e2 
796: epoch: Remove ptr-to-int casts r=taiki-e a=taiki-e

Use [this hack](rust-lang/miri#1866 (comment)) to fix compatibility issues with Miri (see #490 (comment) for details). 

Due to the #545, still not compatible with stacked borrows. This will be fixed by the subsequent PR (#871).

Note: this is a breaking change because changes API of Pointable and Pointer traits

Fixes #579

Co-authored-by: Taiki Endo <te316e89@gmail.com>
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from 86c1680 to 525ae4f Compare July 23, 2022 08:50
@taiki-e taiki-e requested a review from jeehoonkang July 23, 2022 10:53
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch 2 times, most recently from a8485b4 to f93970c Compare July 23, 2022 12:06
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from f93970c to 9d1ebd2 Compare September 23, 2022 10:23
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from 48e0dfd to be5bcc4 Compare November 20, 2022 08:04
taiki-e
taiki-e commented Nov 20, 2022
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crossbeam-epoch/src/atomic.rs Outdated
/// - `ptr` should not be mutably dereferenced by [`Pointable::deref_mut`] concurrently.
unsafe fn deref<'a>(ptr: *mut ()) -> &'a Self;
/// - `ptr` should not be mutably dereferenced by [`Pointable::as_mut_ptr`] concurrently.
unsafe fn as_ptr(ptr: *mut ()) -> *const Self;

/// Mutably dereferences the given pointer.
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This is no longer a dereference, but I'm not sure what is a good API name and description.

@taiki-e taiki-e marked this pull request as draft November 20, 2022 08:34
@taiki-e taiki-e marked this pull request as ready for review November 20, 2022 08:37
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from be5bcc4 to 87eecad Compare December 16, 2022 13:41
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from 87eecad to f0f7323 Compare December 27, 2022 14:43
@taiki-e taiki-e mentioned this pull request Jan 30, 2023
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@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from f0f7323 to 6bd2fda Compare June 17, 2023 11:20
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taiki-e commented Jun 17, 2023

(Given that Miri appears to be trying to move to TB in the long term, I don't see the need to rush to merge this.)

@taiki-e taiki-e mentioned this pull request Jun 17, 2023
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@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from 6bd2fda to a3fec7d Compare June 17, 2023 13:11
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@taiki-e taiki-e mentioned this pull request Feb 20, 2025
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(Given that Miri appears to be trying to move to TB in the long term, I don't see the need to rush to merge this.)

Is this documented anywhere and current?

Miri's README currently says:

While Tree Borrows is still sound in the sense of catching all aliasing violations that current versions of the compiler might exploit, it is likely that the eventual final aliasing model of Rust will be stricter than Tree Borrows. In other words, if you use Tree Borrows, even if your code is accepted today, it might be declared UB in the future. This is much less likely with Stacked Borrows. Using Tree Borrows currently implies -Zmiri-strict-provenance because integer-to-pointer casts are not supported in this mode, but that may change in the future.

@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch 2 times, most recently from 353cb51 to 689bbdc Compare March 20, 2025 19:44
@taiki-e taiki-e force-pushed the epoch-fix-sb-violations branch from 689bbdc to a5fcbd3 Compare March 20, 2025 19:52
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epoch: Miri reports SB violation
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