Don't hold the predecessor cache lock longer than necessary #71392
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☔ The latest upstream changes (presumably #71323) made this pull request unmergeable. Please resolve the merge conflicts. |
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There is no `Arc::map` equivalent to `LockGuard::map`
...instead of a `LockGuard` which means the lock is held for longer than necessary.
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…he-arc, r=nikomatsakis Don't hold the predecessor cache lock longer than necessary rust-lang#71044 returns a `LockGuard` with the predecessor cache to callers of `Body::predecessors`. As a result, the lock around the predecessor cache could be held for an arbitrarily long time. This PR uses reference counting for ownership of the predecessor cache, meaning the lock is only ever held within `PredecessorCache::compute`. Checking this API for potential sources of deadlock is much easier now, since we no longer have to consider its consumers, only its internals. This required removing `predecessors_for`, since there is no equivalent to `LockGuard::map` for `Arc` and `Rc`. I believe this could be emulated with `owning_ref::{Arc,Rc}Ref`, but I don't think it's necessary. Also, we continue to return an opaque type from `Body::predecessors` with the lifetime of the `Body`, not `'static`. This depends on rust-lang#71044. Only the last two commits are new. r? @nikomatsakis
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…he-arc, r=nikomatsakis Don't hold the predecessor cache lock longer than necessary rust-lang#71044 returns a `LockGuard` with the predecessor cache to callers of `Body::predecessors`. As a result, the lock around the predecessor cache could be held for an arbitrarily long time. This PR uses reference counting for ownership of the predecessor cache, meaning the lock is only ever held within `PredecessorCache::compute`. Checking this API for potential sources of deadlock is much easier now, since we no longer have to consider its consumers, only its internals. This required removing `predecessors_for`, since there is no equivalent to `LockGuard::map` for `Arc` and `Rc`. I believe this could be emulated with `owning_ref::{Arc,Rc}Ref`, but I don't think it's necessary. Also, we continue to return an opaque type from `Body::predecessors` with the lifetime of the `Body`, not `'static`. This depends on rust-lang#71044. Only the last two commits are new. r? @nikomatsakis
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Rollup of 5 pull requests Successful merges: - rust-lang#70043 (Add all remaining `DefKind`s.) - rust-lang#71140 ([breaking change] Disallow statics initializing themselves) - rust-lang#71392 (Don't hold the predecessor cache lock longer than necessary) - rust-lang#71541 (Add regression test for rust-lang#26376) - rust-lang#71554 (Replace thread_local with generator resume arguments in box_region.) Failed merges: r? @ghost
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#71044 returns a
LockGuardwith the predecessor cache to callers ofBody::predecessors. As a result, the lock around the predecessor cache could be held for an arbitrarily long time. This PR uses reference counting for ownership of the predecessor cache, meaning the lock is only ever held withinPredecessorCache::compute. Checking this API for potential sources of deadlock is much easier now, since we no longer have to consider its consumers, only its internals.This required removing
predecessors_for, since there is no equivalent toLockGuard::mapforArcandRc. I believe this could be emulated withowning_ref::{Arc,Rc}Ref, but I don't think it's necessary. Also, we continue to return an opaque type fromBody::predecessorswith the lifetime of theBody, not'static.This depends on #71044. Only the last two commits are new.
r? @nikomatsakis