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Copy paththread_mutex.rs
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327 lines (307 loc) · 9.72 KB
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#![allow(clippy::needless_lifetimes)]
use alloc::fmt;
use core::{
cell::UnsafeCell,
marker::PhantomData,
ops::{Deref, DerefMut},
ptr::NonNull,
sync::atomic::{AtomicUsize, Ordering},
};
use lock_api::{GetThreadId, GuardNoSend, RawMutex};
// based off ReentrantMutex from lock_api
/// A mutex type that knows when it would deadlock
pub struct RawThreadMutex<R: RawMutex, G: GetThreadId> {
owner: AtomicUsize,
mutex: R,
get_thread_id: G,
}
impl<R: RawMutex, G: GetThreadId> RawThreadMutex<R, G> {
#[allow(
clippy::declare_interior_mutable_const,
reason = "const initializer for lock primitive contains atomics by design"
)]
pub const INIT: Self = Self {
owner: AtomicUsize::new(0),
mutex: R::INIT,
get_thread_id: G::INIT,
};
#[inline]
fn lock_internal<F: FnOnce() -> bool>(&self, try_lock: F) -> Option<bool> {
let id = self.get_thread_id.nonzero_thread_id().get();
if self.owner.load(Ordering::Relaxed) == id {
return None;
} else {
if !try_lock() {
return Some(false);
}
self.owner.store(id, Ordering::Relaxed);
}
Some(true)
}
/// Blocks for the mutex to be available, and returns true if the mutex isn't already
/// locked on the current thread.
pub fn lock(&self) -> bool {
self.lock_internal(|| {
self.mutex.lock();
true
})
.is_some()
}
/// Returns `Some(true)` if able to successfully lock without blocking, `Some(false)`
/// otherwise, and `None` when the mutex is already locked on the current thread.
pub fn try_lock(&self) -> Option<bool> {
self.lock_internal(|| self.mutex.try_lock())
}
/// Unlocks this mutex. The inner mutex may not be unlocked if
/// this mutex was acquired previously in the current thread.
///
/// # Safety
///
/// This method may only be called if the mutex is held by the current thread.
pub unsafe fn unlock(&self) {
self.owner.store(0, Ordering::Relaxed);
unsafe { self.mutex.unlock() };
}
}
impl<R: RawMutex, G: GetThreadId> RawThreadMutex<R, G> {
/// Reset this mutex to its initial (unlocked, unowned) state after `fork()`.
///
/// # Safety
///
/// Must only be called from the single-threaded child process immediately
/// after `fork()`, before any other thread is created.
#[cfg(unix)]
pub unsafe fn reinit_after_fork(&self) {
self.owner.store(0, Ordering::Relaxed);
unsafe {
let mutex_ptr = &self.mutex as *const R as *mut u8;
core::ptr::write_bytes(mutex_ptr, 0, core::mem::size_of::<R>());
}
}
}
unsafe impl<R: RawMutex + Send, G: GetThreadId + Send> Send for RawThreadMutex<R, G> {}
unsafe impl<R: RawMutex + Sync, G: GetThreadId + Sync> Sync for RawThreadMutex<R, G> {}
pub struct ThreadMutex<R: RawMutex, G: GetThreadId, T: ?Sized> {
raw: RawThreadMutex<R, G>,
data: UnsafeCell<T>,
}
impl<R: RawMutex, G: GetThreadId, T> ThreadMutex<R, G, T> {
pub const fn new(val: T) -> Self {
Self {
raw: RawThreadMutex::INIT,
data: UnsafeCell::new(val),
}
}
pub fn into_inner(self) -> T {
self.data.into_inner()
}
}
impl<R: RawMutex, G: GetThreadId, T: Default> Default for ThreadMutex<R, G, T> {
fn default() -> Self {
Self::new(T::default())
}
}
impl<R: RawMutex, G: GetThreadId, T> From<T> for ThreadMutex<R, G, T> {
fn from(val: T) -> Self {
Self::new(val)
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> ThreadMutex<R, G, T> {
/// Access the underlying raw thread mutex.
pub fn raw(&self) -> &RawThreadMutex<R, G> {
&self.raw
}
pub fn lock(&self) -> Option<ThreadMutexGuard<'_, R, G, T>> {
if self.raw.lock() {
Some(ThreadMutexGuard {
mu: self,
marker: PhantomData,
})
} else {
None
}
}
pub fn try_lock(&self) -> Result<ThreadMutexGuard<'_, R, G, T>, TryLockThreadError> {
match self.raw.try_lock() {
Some(true) => Ok(ThreadMutexGuard {
mu: self,
marker: PhantomData,
}),
Some(false) => Err(TryLockThreadError::Other),
None => Err(TryLockThreadError::Current),
}
}
}
#[derive(Clone, Copy)]
pub enum TryLockThreadError {
/// Failed to lock because mutex was already locked on another thread.
Other,
/// Failed to lock because mutex was already locked on current thread.
Current,
}
struct LockedPlaceholder(&'static str);
impl fmt::Debug for LockedPlaceholder {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(self.0)
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized + fmt::Debug> fmt::Debug for ThreadMutex<R, G, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.try_lock() {
Ok(guard) => f
.debug_struct("ThreadMutex")
.field("data", &&*guard)
.finish(),
Err(e) => {
let msg = match e {
TryLockThreadError::Other => "<locked on other thread>",
TryLockThreadError::Current => "<locked on current thread>",
};
f.debug_struct("ThreadMutex")
.field("data", &LockedPlaceholder(msg))
.finish()
}
}
}
}
unsafe impl<R: RawMutex + Send, G: GetThreadId + Send, T: ?Sized + Send> Send
for ThreadMutex<R, G, T>
{
}
unsafe impl<R: RawMutex + Sync, G: GetThreadId + Sync, T: ?Sized + Send> Sync
for ThreadMutex<R, G, T>
{
}
pub struct ThreadMutexGuard<'a, R: RawMutex, G: GetThreadId, T: ?Sized> {
mu: &'a ThreadMutex<R, G, T>,
marker: PhantomData<(&'a mut T, GuardNoSend)>,
}
impl<'a, R: RawMutex, G: GetThreadId, T: ?Sized> ThreadMutexGuard<'a, R, G, T> {
pub fn map<U, F: FnOnce(&mut T) -> &mut U>(
mut s: Self,
f: F,
) -> MappedThreadMutexGuard<'a, R, G, U> {
let data = f(&mut s).into();
let mu = &s.mu.raw;
core::mem::forget(s);
MappedThreadMutexGuard {
mu,
data,
marker: PhantomData,
}
}
pub fn try_map<U, F: FnOnce(&mut T) -> Option<&mut U>>(
mut s: Self,
f: F,
) -> Result<MappedThreadMutexGuard<'a, R, G, U>, Self> {
if let Some(data) = f(&mut s) {
let data = data.into();
let mu = &s.mu.raw;
core::mem::forget(s);
Ok(MappedThreadMutexGuard {
mu,
data,
marker: PhantomData,
})
} else {
Err(s)
}
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> Deref for ThreadMutexGuard<'_, R, G, T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { &*self.mu.data.get() }
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> DerefMut for ThreadMutexGuard<'_, R, G, T> {
fn deref_mut(&mut self) -> &mut T {
unsafe { &mut *self.mu.data.get() }
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> Drop for ThreadMutexGuard<'_, R, G, T> {
fn drop(&mut self) {
unsafe { self.mu.raw.unlock() }
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized + fmt::Display> fmt::Display
for ThreadMutexGuard<'_, R, G, T>
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(&**self, f)
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized + fmt::Debug> fmt::Debug
for ThreadMutexGuard<'_, R, G, T>
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&**self, f)
}
}
pub struct MappedThreadMutexGuard<'a, R: RawMutex, G: GetThreadId, T: ?Sized> {
mu: &'a RawThreadMutex<R, G>,
data: NonNull<T>,
marker: PhantomData<(&'a mut T, GuardNoSend)>,
}
impl<'a, R: RawMutex, G: GetThreadId, T: ?Sized> MappedThreadMutexGuard<'a, R, G, T> {
pub fn map<U, F: FnOnce(&mut T) -> &mut U>(
mut s: Self,
f: F,
) -> MappedThreadMutexGuard<'a, R, G, U> {
let data = f(&mut s).into();
let mu = s.mu;
core::mem::forget(s);
MappedThreadMutexGuard {
mu,
data,
marker: PhantomData,
}
}
pub fn try_map<U, F: FnOnce(&mut T) -> Option<&mut U>>(
mut s: Self,
f: F,
) -> Result<MappedThreadMutexGuard<'a, R, G, U>, Self> {
if let Some(data) = f(&mut s) {
let data = data.into();
let mu = s.mu;
core::mem::forget(s);
Ok(MappedThreadMutexGuard {
mu,
data,
marker: PhantomData,
})
} else {
Err(s)
}
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> Deref for MappedThreadMutexGuard<'_, R, G, T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { self.data.as_ref() }
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> DerefMut for MappedThreadMutexGuard<'_, R, G, T> {
fn deref_mut(&mut self) -> &mut T {
unsafe { self.data.as_mut() }
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized> Drop for MappedThreadMutexGuard<'_, R, G, T> {
fn drop(&mut self) {
unsafe { self.mu.unlock() }
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized + fmt::Display> fmt::Display
for MappedThreadMutexGuard<'_, R, G, T>
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Display::fmt(&**self, f)
}
}
impl<R: RawMutex, G: GetThreadId, T: ?Sized + fmt::Debug> fmt::Debug
for MappedThreadMutexGuard<'_, R, G, T>
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&**self, f)
}
}