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SeqCst->{Release,Acquire} in xous mutex.

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No need for SeqCst. Release+Acquire is the right memory ordering for a
mutex.
This commit is contained in:
Mara Bos
2024-03-19 15:00:09 +01:00
parent 9f25a04498
commit eb966983f2
1 changed files with 7 additions and 4 deletions
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11
library/std/src/sys/sync/mutex/xous.rs
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@@ -1,6 +1,9 @@
use crate::os::xous::ffi::{blocking_scalar, do_yield}; use crate::os::xous::ffi::{blocking_scalar, do_yield};
use crate::os::xous::services::{ticktimer_server, TicktimerScalar}; use crate::os::xous::services::{ticktimer_server, TicktimerScalar};
use crate::sync::atomic::{AtomicBool, AtomicUsize, Ordering::Relaxed, Ordering::SeqCst}; use crate::sync::atomic::{
AtomicBool, AtomicUsize,
Ordering::{Acquire, Relaxed, Release},
};
pub struct Mutex { pub struct Mutex {
/// The "locked" value indicates how many threads are waiting on this /// The "locked" value indicates how many threads are waiting on this
@@ -68,7 +71,7 @@ impl Mutex {
#[inline] #[inline]
pub unsafe fn unlock(&self) { pub unsafe fn unlock(&self) {
let prev = self.locked.fetch_sub(1, SeqCst); let prev = self.locked.fetch_sub(1, Release);
// If the previous value was 1, then this was a "fast path" unlock, so no // If the previous value was 1, then this was a "fast path" unlock, so no
// need to involve the Ticktimer server // need to involve the Ticktimer server
@@ -89,12 +92,12 @@ impl Mutex {
#[inline] #[inline]
pub unsafe fn try_lock(&self) -> bool { pub unsafe fn try_lock(&self) -> bool {
self.locked.compare_exchange(0, 1, SeqCst, SeqCst).is_ok() self.locked.compare_exchange(0, 1, Acquire, Relaxed).is_ok()
} }
#[inline] #[inline]
pub unsafe fn try_lock_or_poison(&self) -> bool { pub unsafe fn try_lock_or_poison(&self) -> bool {
self.locked.fetch_add(1, SeqCst) == 0 self.locked.fetch_add(1, Acquire) == 0
} }
} }