1 use crate::cell::UnsafeCell;
2 use crate::mem::MaybeUninit;
4 pub struct Mutex { inner: UnsafeCell<libc::pthread_mutex_t> }
7 pub unsafe fn raw(m: &Mutex) -> *mut libc::pthread_mutex_t {
11 unsafe impl Send for Mutex {}
12 unsafe impl Sync for Mutex {}
14 #[allow(dead_code)] // sys isn't exported yet
16 pub const fn new() -> Mutex {
17 // Might be moved to a different address, so it is better to avoid
18 // initialization of potentially opaque OS data before it landed.
19 // Be very careful using this newly constructed `Mutex`, reentrant
20 // locking is undefined behavior until `init` is called!
21 Mutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
24 pub unsafe fn init(&mut self) {
27 // A pthread mutex initialized with PTHREAD_MUTEX_INITIALIZER will have
28 // a type of PTHREAD_MUTEX_DEFAULT, which has undefined behavior if you
29 // try to re-lock it from the same thread when you already hold a lock.
31 // In practice, glibc takes advantage of this undefined behavior to
32 // implement hardware lock elision, which uses hardware transactional
33 // memory to avoid acquiring the lock. While a transaction is in
34 // progress, the lock appears to be unlocked. This isn't a problem for
35 // other threads since the transactional memory will abort if a conflict
36 // is detected, however no abort is generated if re-locking from the
39 // Since locking the same mutex twice will result in two aliasing &mut
40 // references, we instead create the mutex with type
41 // PTHREAD_MUTEX_NORMAL which is guaranteed to deadlock if we try to
42 // re-lock it from the same thread, thus avoiding undefined behavior.
43 let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
44 let r = libc::pthread_mutexattr_init(attr.as_mut_ptr());
45 debug_assert_eq!(r, 0);
46 let r = libc::pthread_mutexattr_settype(attr.as_mut_ptr(), libc::PTHREAD_MUTEX_NORMAL);
47 debug_assert_eq!(r, 0);
48 let r = libc::pthread_mutex_init(self.inner.get(), attr.as_ptr());
49 debug_assert_eq!(r, 0);
50 let r = libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
51 debug_assert_eq!(r, 0);
54 pub unsafe fn lock(&self) {
55 let r = libc::pthread_mutex_lock(self.inner.get());
56 debug_assert_eq!(r, 0);
59 pub unsafe fn unlock(&self) {
60 let r = libc::pthread_mutex_unlock(self.inner.get());
61 debug_assert_eq!(r, 0);
64 pub unsafe fn try_lock(&self) -> bool {
65 libc::pthread_mutex_trylock(self.inner.get()) == 0
68 #[cfg(not(target_os = "dragonfly"))]
69 pub unsafe fn destroy(&self) {
70 let r = libc::pthread_mutex_destroy(self.inner.get());
71 debug_assert_eq!(r, 0);
74 #[cfg(target_os = "dragonfly")]
75 pub unsafe fn destroy(&self) {
76 let r = libc::pthread_mutex_destroy(self.inner.get());
77 // On DragonFly pthread_mutex_destroy() returns EINVAL if called on a
78 // mutex that was just initialized with libc::PTHREAD_MUTEX_INITIALIZER.
79 // Once it is used (locked/unlocked) or pthread_mutex_init() is called,
80 // this behaviour no longer occurs.
81 debug_assert!(r == 0 || r == libc::EINVAL);
85 pub struct ReentrantMutex { inner: UnsafeCell<libc::pthread_mutex_t> }
87 unsafe impl Send for ReentrantMutex {}
88 unsafe impl Sync for ReentrantMutex {}
91 pub unsafe fn uninitialized() -> ReentrantMutex {
92 ReentrantMutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
95 pub unsafe fn init(&mut self) {
96 let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
97 let result = libc::pthread_mutexattr_init(attr.as_mut_ptr());
98 debug_assert_eq!(result, 0);
99 let result = libc::pthread_mutexattr_settype(attr.as_mut_ptr(),
100 libc::PTHREAD_MUTEX_RECURSIVE);
101 debug_assert_eq!(result, 0);
102 let result = libc::pthread_mutex_init(self.inner.get(), attr.as_ptr());
103 debug_assert_eq!(result, 0);
104 let result = libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
105 debug_assert_eq!(result, 0);
108 pub unsafe fn lock(&self) {
109 let result = libc::pthread_mutex_lock(self.inner.get());
110 debug_assert_eq!(result, 0);
114 pub unsafe fn try_lock(&self) -> bool {
115 libc::pthread_mutex_trylock(self.inner.get()) == 0
118 pub unsafe fn unlock(&self) {
119 let result = libc::pthread_mutex_unlock(self.inner.get());
120 debug_assert_eq!(result, 0);
123 pub unsafe fn destroy(&self) {
124 let result = libc::pthread_mutex_destroy(self.inner.get());
125 debug_assert_eq!(result, 0);