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// SPDX-License-Identifier: Apache-2.0 OR MIT
// inspired by <https://github.com/nbdd0121/pin-init/blob/trunk/examples/pthread_mutex.rs>
#![allow(clippy::undocumented_unsafe_blocks)]
#![cfg_attr(feature = "alloc", feature(allocator_api))]
#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
#[cfg(not(windows))]
mod pthread_mtx {
#[cfg(feature = "alloc")]
use core::alloc::AllocError;
use core::{
cell::UnsafeCell,
marker::PhantomPinned,
mem::MaybeUninit,
ops::{Deref, DerefMut},
pin::Pin,
};
use pin_init::*;
use std::convert::Infallible;
#[pin_data(PinnedDrop)]
pub struct PThreadMutex<T> {
#[pin]
raw: UnsafeCell<libc::pthread_mutex_t>,
data: UnsafeCell<T>,
#[pin]
pin: PhantomPinned,
}
unsafe impl<T: Send> Send for PThreadMutex<T> {}
unsafe impl<T: Send> Sync for PThreadMutex<T> {}
#[pinned_drop]
impl<T> PinnedDrop for PThreadMutex<T> {
fn drop(self: Pin<&mut Self>) {
unsafe {
libc::pthread_mutex_destroy(self.raw.get());
}
}
}
#[derive(Debug)]
pub enum Error {
#[allow(dead_code)]
IO(std::io::Error),
#[allow(dead_code)]
Alloc,
}
impl From<Infallible> for Error {
fn from(e: Infallible) -> Self {
match e {}
}
}
#[cfg(feature = "alloc")]
impl From<AllocError> for Error {
fn from(_: AllocError) -> Self {
Self::Alloc
}
}
impl<T> PThreadMutex<T> {
#[allow(dead_code)]
pub fn new(data: T) -> impl PinInit<Self, Error> {
fn init_raw() -> impl PinInit<UnsafeCell<libc::pthread_mutex_t>, Error> {
let init = |slot: *mut UnsafeCell<libc::pthread_mutex_t>| {
// we can cast, because `UnsafeCell` has the same layout as T.
let slot: *mut libc::pthread_mutex_t = slot.cast();
let mut attr = MaybeUninit::uninit();
let attr = attr.as_mut_ptr();
// SAFETY: ptr is valid
let ret = unsafe { libc::pthread_mutexattr_init(attr) };
if ret != 0 {
return Err(Error::IO(std::io::Error::from_raw_os_error(ret)));
}
// SAFETY: attr is initialized
let ret = unsafe {
libc::pthread_mutexattr_settype(attr, libc::PTHREAD_MUTEX_NORMAL)
};
if ret != 0 {
// SAFETY: attr is initialized
unsafe { libc::pthread_mutexattr_destroy(attr) };
return Err(Error::IO(std::io::Error::from_raw_os_error(ret)));
}
// SAFETY: slot is valid
unsafe { slot.write(libc::PTHREAD_MUTEX_INITIALIZER) };
// SAFETY: attr and slot are valid ptrs and attr is initialized
let ret = unsafe { libc::pthread_mutex_init(slot, attr) };
// SAFETY: attr was initialized
unsafe { libc::pthread_mutexattr_destroy(attr) };
if ret != 0 {
return Err(Error::IO(std::io::Error::from_raw_os_error(ret)));
}
Ok(())
};
// SAFETY: mutex has been initialized
unsafe { pin_init_from_closure(init) }
}
try_pin_init!(Self {
data: UnsafeCell::new(data),
raw <- init_raw(),
pin: PhantomPinned,
}? Error)
}
#[allow(dead_code)]
pub fn lock(&self) -> PThreadMutexGuard<'_, T> {
// SAFETY: raw is always initialized
unsafe { libc::pthread_mutex_lock(self.raw.get()) };
PThreadMutexGuard { mtx: self }
}
}
pub struct PThreadMutexGuard<'a, T> {
mtx: &'a PThreadMutex<T>,
}
impl<T> Drop for PThreadMutexGuard<'_, T> {
fn drop(&mut self) {
// SAFETY: raw is always initialized
unsafe { libc::pthread_mutex_unlock(self.mtx.raw.get()) };
}
}
impl<T> Deref for PThreadMutexGuard<'_, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
unsafe { &*self.mtx.data.get() }
}
}
impl<T> DerefMut for PThreadMutexGuard<'_, T> {
fn deref_mut(&mut self) -> &mut Self::Target {
unsafe { &mut *self.mtx.data.get() }
}
}
}
#[cfg_attr(test, test)]
#[cfg_attr(all(test, miri), ignore)]
fn main() {
#[cfg(all(any(feature = "std", feature = "alloc"), not(windows)))]
{
use core::pin::Pin;
use pin_init::*;
use pthread_mtx::*;
use std::{
sync::Arc,
thread::{sleep, Builder},
time::Duration,
};
let mtx: Pin<Arc<PThreadMutex<usize>>> = Arc::try_pin_init(PThreadMutex::new(0)).unwrap();
let mut handles = vec![];
let thread_count = 20;
let workload = 1_000_000;
for i in 0..thread_count {
let mtx = mtx.clone();
handles.push(
Builder::new()
.name(format!("worker #{i}"))
.spawn(move || {
for _ in 0..workload {
*mtx.lock() += 1;
}
println!("{i} halfway");
sleep(Duration::from_millis((i as u64) * 10));
for _ in 0..workload {
*mtx.lock() += 1;
}
println!("{i} finished");
})
.expect("should not fail"),
);
}
for h in handles {
h.join().expect("thread panicked");
}
println!("{:?}", &*mtx.lock());
assert_eq!(*mtx.lock(), workload * thread_count * 2);
}
}
|
