bjoernager/rust
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Remove unsafety from unsupported/rwlosck.rs by using a Cell.

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Replacing the UnsafeCell by a Cell makes it all safe.
This commit is contained in:
Mara Bos 2020-10-08 22:52:26 +02:00
parent c25f69a1e3
commit 3d192ace34
1 changed files with 16 additions and 18 deletions
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34
library/std/src/sys/unsupported/rwlock.rs
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@ -1,7 +1,9 @@
use crate::cell::UnsafeCell; #![deny(unsafe_op_in_unsafe_fn)]
use crate::cell::Cell;
pub struct RWLock { pub struct RWLock {
mode: UnsafeCell<isize>, mode: Cell<isize>,
} }
unsafe impl Send for RWLock {} unsafe impl Send for RWLock {}
@ -9,14 +11,14 @@ unsafe impl Sync for RWLock {} // no threads on this platform
impl RWLock { impl RWLock {
pub const fn new() -> RWLock { pub const fn new() -> RWLock {
RWLock { mode: UnsafeCell::new(0) } RWLock { mode: Cell::new(0) }
} }
#[inline] #[inline]
pub unsafe fn read(&self) { pub unsafe fn read(&self) {
let mode = self.mode.get(); let m = self.mode.get();
if *mode >= 0 { if m >= 0 {
*mode += 1; self.mode.set(m + 1);
} else { } else {
rtabort!("rwlock locked for writing"); rtabort!("rwlock locked for writing");
} }
@ -24,9 +26,9 @@ impl RWLock {
#[inline] #[inline]
pub unsafe fn try_read(&self) -> bool { pub unsafe fn try_read(&self) -> bool {
let mode = self.mode.get(); let m = self.mode.get();
if *mode >= 0 { if m >= 0 {
*mode += 1; self.mode.set(m + 1);
true true
} else { } else {
false false
@ -35,19 +37,15 @@ impl RWLock {
#[inline] #[inline]
pub unsafe fn write(&self) { pub unsafe fn write(&self) {
let mode = self.mode.get(); if self.mode.replace(-1) != 0 {
if *mode == 0 {
*mode = -1;
} else {
rtabort!("rwlock locked for reading") rtabort!("rwlock locked for reading")
} }
} }
#[inline] #[inline]
pub unsafe fn try_write(&self) -> bool { pub unsafe fn try_write(&self) -> bool {
let mode = self.mode.get(); if self.mode.get() == 0 {
if *mode == 0 { self.mode.set(-1);
*mode = -1;
true true
} else { } else {
false false
@ -56,12 +54,12 @@ impl RWLock {
#[inline] #[inline]
pub unsafe fn read_unlock(&self) { pub unsafe fn read_unlock(&self) {
*self.mode.get() -= 1; self.mode.set(self.mode.get() - 1);
} }
#[inline] #[inline]
pub unsafe fn write_unlock(&self) { pub unsafe fn write_unlock(&self) {
*self.mode.get() += 1; self.mode.set(0);
} }
#[inline] #[inline]