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Get rid of UnsafeCell<MaybeUninit>s in cloudabi mutex.

This commit is contained in:
Mara Bos 2020-10-07 18:16:02 +02:00
parent e6d61ade9c
commit 0f26578f2e
1 changed files with 24 additions and 28 deletions
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52
library/std/src/sys/cloudabi/mutex.rs
View File

@ -1,4 +1,4 @@
use crate::cell::UnsafeCell;
use crate::cell::Cell;
use crate::mem;
use crate::mem::MaybeUninit;
use crate::sync::atomic::{AtomicU32, Ordering};
@ -50,28 +50,23 @@ impl Mutex {
}
pub struct ReentrantMutex {
lock: UnsafeCell<MaybeUninit<AtomicU32>>,
recursion: UnsafeCell<MaybeUninit<u32>>,
lock: AtomicU32,
recursion: Cell<u32>,
}
unsafe impl Send for ReentrantMutex {}
unsafe impl Sync for ReentrantMutex {}
impl ReentrantMutex {
pub const unsafe fn uninitialized() -> ReentrantMutex {
ReentrantMutex {
lock: UnsafeCell::new(MaybeUninit::uninit()),
recursion: UnsafeCell::new(MaybeUninit::uninit()),
}
ReentrantMutex { lock: AtomicU32::new(abi::LOCK_UNLOCKED.0), recursion: Cell::new(0) }
}
pub unsafe fn init(&self) {
*self.lock.get() = MaybeUninit::new(AtomicU32::new(abi::LOCK_UNLOCKED.0));
*self.recursion.get() = MaybeUninit::new(0);
}
pub unsafe fn init(&self) {}
pub unsafe fn try_lock(&self) -> bool {
// Attempt to acquire the lock.
let lock = (*self.lock.get()).as_mut_ptr();
let recursion = (*self.recursion.get()).as_mut_ptr();
if let Err(old) = (*lock).compare_exchange(
if let Err(old) = self.lock.compare_exchange(
abi::LOCK_UNLOCKED.0,
__pthread_thread_id.0 | abi::LOCK_WRLOCKED.0,
Ordering::Acquire,
@ -80,14 +75,14 @@ impl ReentrantMutex {
// If we fail to acquire the lock, it may be the case
// that we've already acquired it and may need to recurse.
if old & !abi::LOCK_KERNEL_MANAGED.0 == __pthread_thread_id.0 | abi::LOCK_WRLOCKED.0 {
*recursion += 1;
self.recursion.set(self.recursion.get() + 1);
true
} else {
false
}
} else {
// Success.
assert_eq!(*recursion, 0, "Mutex has invalid recursion count");
assert_eq!(self.recursion.get(), 0, "Mutex has invalid recursion count");
true
}
}
@ -95,7 +90,7 @@ impl ReentrantMutex {
pub unsafe fn lock(&self) {
if !self.try_lock() {
// Call into the kernel to acquire a write lock.
let lock = self.lock.get();
let lock = &self.lock as *const AtomicU32;
let subscription = abi::subscription {
type_: abi::eventtype::LOCK_WRLOCK,
union: abi::subscription_union {
@ -116,17 +111,17 @@ impl ReentrantMutex {
}
pub unsafe fn unlock(&self) {
let lock = (*self.lock.get()).as_mut_ptr();
let recursion = (*self.recursion.get()).as_mut_ptr();
assert_eq!(
(*lock).load(Ordering::Relaxed) & !abi::LOCK_KERNEL_MANAGED.0,
self.lock.load(Ordering::Relaxed) & !abi::LOCK_KERNEL_MANAGED.0,
__pthread_thread_id.0 | abi::LOCK_WRLOCKED.0,
"This mutex is locked by a different thread"
);
if *recursion > 0 {
*recursion -= 1;
} else if !(*lock)
let r = self.recursion.get();
if r > 0 {
self.recursion.set(r - 1);
} else if !self
.lock
.compare_exchange(
__pthread_thread_id.0 | abi::LOCK_WRLOCKED.0,
abi::LOCK_UNLOCKED.0,
@ -137,19 +132,20 @@ impl ReentrantMutex {
{
// Lock is managed by kernelspace. Call into the kernel
// to unblock waiting threads.
let ret = abi::lock_unlock(lock as *mut abi::lock, abi::scope::PRIVATE);
let ret = abi::lock_unlock(
&self.lock as *const AtomicU32 as *mut abi::lock,
abi::scope::PRIVATE,
);
assert_eq!(ret, abi::errno::SUCCESS, "Failed to unlock a mutex");
}
}
pub unsafe fn destroy(&self) {
let lock = (*self.lock.get()).as_mut_ptr();
let recursion = (*self.recursion.get()).as_mut_ptr();
assert_eq!(
(*lock).load(Ordering::Relaxed),
self.lock.load(Ordering::Relaxed),
abi::LOCK_UNLOCKED.0,
"Attempted to destroy locked mutex"
);
assert_eq!(*recursion, 0, "Recursion counter invalid");
assert_eq!(self.recursion.get(), 0, "Recursion counter invalid");
}
}