parking_lot

Kinogaki's own parking_lot, published under the crates.io name so the frozen wgpu, wgpu-core and wgpu-hal resolve to it through [patch.crates-io]. It is not upstream parking_lot: it has the lock API those crates call, with parking_lot's semantics where they rely on them:

• no poisoning: a panic while a lock is held leaves it usable;
• Condvar waits take the guard by &mut and return a timeout result;
• RwLock is writer-preferring (task-fair): once a writer waits, new readers wait behind it, so writers are never starved and a thread that reads recursively while a writer waits deadlocks, as with parking_lot. (wgpu-core never re-reads a lock it holds; its lock ranks forbid it.)
• RwLockReadGuard can be forgotten and its read released later with RwLock::force_unlock_read (wgpu-core's snatch lock does this).

Mutex and Condvar wrap std's. RwLock keeps its state in one atomic word (an uncontended read or write is one compare-exchange) and parks waiters on a std mutex and condition variable; its data cell is the crate's only unsafe code (src/rwlock/cell.rs).