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Replace pthread RwLock with custom implementation #110211

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Merged
bors merged 12 commits into from
Feb 12, 2024
Merged

Replace pthread RwLock with custom implementation #110211

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934eb8b
std: replace pthread `RwLock` with custom implementation inspired by …
joboet Apr 11, 2023
2e652e5
adjust code documentation
joboet Apr 12, 2023
280cbc5
use braces to make operator precedence less ambiguous
joboet Apr 12, 2023
709ccf9
avoid unnecessary `Thread` handle allocation
joboet Apr 12, 2023
61ce691
immediately register writer node if threads are queued
joboet Apr 18, 2023
8db64b5
use exponential backoff in `lock_contended`
joboet Apr 18, 2023
16aae04
queue_rwlock: use a separate `QUEUE_LOCKED` bit to synchronize waiter…
joboet Apr 18, 2023
1fd9f78
inline some single-use functions, add documentation
joboet Apr 22, 2023
69f55de
format using latest rustfmt
joboet Nov 30, 2023
3fa5a40
be more explicit about why adding backlinks eagerly makes sense
joboet Feb 9, 2024
ff44ae7
address review comments
joboet Feb 9, 2024
04282db
add doc-comment to `unlock_queue`
joboet Feb 11, 2024
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use exponential backoff in lock_contended
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@joboet
joboet committed Feb 9, 2024
commit 8db64b5e2d442cb43830a8849e3549e4f8e20447
6 changes: 4 additions & 2 deletions library/std/src/sys/pal/unix/locks/queue_rwlock.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,7 @@ use crate::sync::atomic::{
use crate::sys_common::thread_info;
use crate::thread::Thread;

const SPIN_COUNT: usize = 100;
const SPIN_COUNT: usize = 6;

type State = *mut ();
type AtomicState = AtomicPtr<()>;
Expand Down Expand Up @@ -328,7 +328,9 @@ impl RwLock {
} else if state.addr() & QUEUED == 0 && count < SPIN_COUNT {
// If the lock is not available but no threads are queued, spin
// for a while.
spin_loop();
for _ in 0..(1 << count) {
spin_loop();
}
state = self.state.load(Relaxed);
count += 1;
} else {
Expand Down