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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 {
mode: UnsafeCell<isize>,
mode: Cell<isize>,
}
unsafe impl Send for RWLock {}
@ -9,14 +11,14 @@ unsafe impl Sync for RWLock {} // no threads on this platform
impl RWLock {
pub const fn new() -> RWLock {
RWLock { mode: UnsafeCell::new(0) }
RWLock { mode: Cell::new(0) }
}
#[inline]
pub unsafe fn read(&self) {
let mode = self.mode.get();
if *mode >= 0 {
*mode += 1;
let m = self.mode.get();
if m >= 0 {
self.mode.set(m + 1);
} else {
rtabort!("rwlock locked for writing");
}
@ -24,9 +26,9 @@ impl RWLock {
#[inline]
pub unsafe fn try_read(&self) -> bool {
let mode = self.mode.get();
if *mode >= 0 {
*mode += 1;
let m = self.mode.get();
if m >= 0 {
self.mode.set(m + 1);
true
} else {
false
@ -35,19 +37,15 @@ impl RWLock {
#[inline]
pub unsafe fn write(&self) {
let mode = self.mode.get();
if *mode == 0 {
*mode = -1;
} else {
if self.mode.replace(-1) != 0 {
rtabort!("rwlock locked for reading")
}
}
#[inline]
pub unsafe fn try_write(&self) -> bool {
let mode = self.mode.get();
if *mode == 0 {
*mode = -1;
if self.mode.get() == 0 {
self.mode.set(-1);
true
} else {
false
@ -56,12 +54,12 @@ impl RWLock {
#[inline]
pub unsafe fn read_unlock(&self) {
*self.mode.get() -= 1;
self.mode.set(self.mode.get() - 1);
}
#[inline]
pub unsafe fn write_unlock(&self) {
*self.mode.get() += 1;
self.mode.set(0);
}
#[inline]