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use crate::cell::UnsafeCell;
use crate::mem::MaybeUninit;
pub struct Mutex { inner: UnsafeCell<libc::pthread_mutex_t> }
#[inline]
pub unsafe fn raw(m: &Mutex) -> *mut libc::pthread_mutex_t {
m.inner.get()
}
unsafe impl Send for Mutex {}
unsafe impl Sync for Mutex {}
#[allow(dead_code)] // sys isn't exported yet
impl Mutex {
pub const fn new() -> Mutex {
// Might be moved to a different address, so it is better to avoid
// initialization of potentially opaque OS data before it landed.
// Be very careful using this newly constructed `Mutex`, reentrant
// locking is undefined behavior until `init` is called!
Mutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
}
#[inline]
pub unsafe fn init(&mut self) {
// Issue #33770
//
// A pthread mutex initialized with PTHREAD_MUTEX_INITIALIZER will have
// a type of PTHREAD_MUTEX_DEFAULT, which has undefined behavior if you
// try to re-lock it from the same thread when you already hold a lock.
//
// In practice, glibc takes advantage of this undefined behavior to
// implement hardware lock elision, which uses hardware transactional
// memory to avoid acquiring the lock. While a transaction is in
// progress, the lock appears to be unlocked. This isn't a problem for
// other threads since the transactional memory will abort if a conflict
// is detected, however no abort is generated if re-locking from the
// same thread.
//
// Since locking the same mutex twice will result in two aliasing &mut
// references, we instead create the mutex with type
// PTHREAD_MUTEX_NORMAL which is guaranteed to deadlock if we try to
// re-lock it from the same thread, thus avoiding undefined behavior.
let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
let r = libc::pthread_mutexattr_init(attr.as_mut_ptr());
debug_assert_eq!(r, 0);
let r = libc::pthread_mutexattr_settype(attr.as_mut_ptr(), libc::PTHREAD_MUTEX_NORMAL);
debug_assert_eq!(r, 0);
let r = libc::pthread_mutex_init(self.inner.get(), attr.as_ptr());
debug_assert_eq!(r, 0);
let r = libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn lock(&self) {
let r = libc::pthread_mutex_lock(self.inner.get());
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn unlock(&self) {
let r = libc::pthread_mutex_unlock(self.inner.get());
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn try_lock(&self) -> bool {
libc::pthread_mutex_trylock(self.inner.get()) == 0
}
#[inline]
#[cfg(not(target_os = "dragonfly"))]
pub unsafe fn destroy(&self) {
let r = libc::pthread_mutex_destroy(self.inner.get());
debug_assert_eq!(r, 0);
}
#[inline]
#[cfg(target_os = "dragonfly")]
pub unsafe fn destroy(&self) {
let r = libc::pthread_mutex_destroy(self.inner.get());
// On DragonFly pthread_mutex_destroy() returns EINVAL if called on a
// mutex that was just initialized with libc::PTHREAD_MUTEX_INITIALIZER.
// Once it is used (locked/unlocked) or pthread_mutex_init() is called,
// this behaviour no longer occurs.
debug_assert!(r == 0 || r == libc::EINVAL);
}
}
pub struct ReentrantMutex { inner: UnsafeCell<libc::pthread_mutex_t> }
unsafe impl Send for ReentrantMutex {}
unsafe impl Sync for ReentrantMutex {}
impl ReentrantMutex {
pub unsafe fn uninitialized() -> ReentrantMutex {
ReentrantMutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
}
pub unsafe fn init(&mut self) {
let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
let result = libc::pthread_mutexattr_init(attr.as_mut_ptr());
debug_assert_eq!(result, 0);
let result = libc::pthread_mutexattr_settype(attr.as_mut_ptr(),
libc::PTHREAD_MUTEX_RECURSIVE);
debug_assert_eq!(result, 0);
let result = libc::pthread_mutex_init(self.inner.get(), attr.as_ptr());
debug_assert_eq!(result, 0);
let result = libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
debug_assert_eq!(result, 0);
}
pub unsafe fn lock(&self) {
let result = libc::pthread_mutex_lock(self.inner.get());
debug_assert_eq!(result, 0);
}
#[inline]
pub unsafe fn try_lock(&self) -> bool {
libc::pthread_mutex_trylock(self.inner.get()) == 0
}
pub unsafe fn unlock(&self) {
let result = libc::pthread_mutex_unlock(self.inner.get());
debug_assert_eq!(result, 0);
}
pub unsafe fn destroy(&self) {
let result = libc::pthread_mutex_destroy(self.inner.get());
debug_assert_eq!(result, 0);
}
}
|
