use crate::sync::atomic::{AtomicUsize, Ordering};
use crate::sys_common::lazy_box::{LazyBox, LazyInit};
-pub struct RwLock {
+struct AllocatedRwLock {
inner: UnsafeCell<libc::pthread_rwlock_t>,
write_locked: UnsafeCell<bool>, // guarded by the `inner` RwLock
num_readers: AtomicUsize,
}
-pub(crate) type MovableRwLock = LazyBox<RwLock>;
+unsafe impl Send for AllocatedRwLock {}
+unsafe impl Sync for AllocatedRwLock {}
-unsafe impl Send for RwLock {}
-unsafe impl Sync for RwLock {}
+pub struct RwLock {
+ inner: LazyBox<AllocatedRwLock>,
+}
-impl LazyInit for RwLock {
+impl LazyInit for AllocatedRwLock {
fn init() -> Box<Self> {
- Box::new(Self::new())
+ Box::new(AllocatedRwLock {
+ inner: UnsafeCell::new(libc::PTHREAD_RWLOCK_INITIALIZER),
+ write_locked: UnsafeCell::new(false),
+ num_readers: AtomicUsize::new(0),
+ })
}
fn destroy(mut rwlock: Box<Self>) {
}
}
+impl AllocatedRwLock {
+ #[inline]
+ unsafe fn raw_unlock(&self) {
+ let r = libc::pthread_rwlock_unlock(self.inner.get());
+ debug_assert_eq!(r, 0);
+ }
+}
+
+impl Drop for AllocatedRwLock {
+ fn drop(&mut self) {
+ let r = unsafe { libc::pthread_rwlock_destroy(self.inner.get()) };
+ // On DragonFly pthread_rwlock_destroy() returns EINVAL if called on a
+ // rwlock that was just initialized with
+ // libc::PTHREAD_RWLOCK_INITIALIZER. Once it is used (locked/unlocked)
+ // or pthread_rwlock_init() is called, this behaviour no longer occurs.
+ if cfg!(target_os = "dragonfly") {
+ debug_assert!(r == 0 || r == libc::EINVAL);
+ } else {
+ debug_assert_eq!(r, 0);
+ }
+ }
+}
+
impl RwLock {
+ #[inline]
pub const fn new() -> RwLock {
- RwLock {
- inner: UnsafeCell::new(libc::PTHREAD_RWLOCK_INITIALIZER),
- write_locked: UnsafeCell::new(false),
- num_readers: AtomicUsize::new(0),
- }
+ RwLock { inner: LazyBox::new() }
}
+
#[inline]
- pub unsafe fn read(&self) {
- let r = libc::pthread_rwlock_rdlock(self.inner.get());
+ pub fn read(&self) {
+ let lock = &*self.inner;
+ let r = unsafe { libc::pthread_rwlock_rdlock(lock.inner.get()) };
// According to POSIX, when a thread tries to acquire this read lock
// while it already holds the write lock
// got the write lock more than once, or got a read and a write lock.
if r == libc::EAGAIN {
panic!("rwlock maximum reader count exceeded");
- } else if r == libc::EDEADLK || (r == 0 && *self.write_locked.get()) {
+ } else if r == libc::EDEADLK || (r == 0 && unsafe { *lock.write_locked.get() }) {
// Above, we make sure to only access `write_locked` when `r == 0` to avoid
// data races.
if r == 0 {
// `pthread_rwlock_rdlock` succeeded when it should not have.
- self.raw_unlock();
+ unsafe {
+ lock.raw_unlock();
+ }
}
panic!("rwlock read lock would result in deadlock");
} else {
// POSIX does not make guarantees about all the errors that may be returned.
// See issue #94705 for more details.
assert_eq!(r, 0, "unexpected error during rwlock read lock: {:?}", r);
- self.num_readers.fetch_add(1, Ordering::Relaxed);
+ lock.num_readers.fetch_add(1, Ordering::Relaxed);
}
}
+
#[inline]
- pub unsafe fn try_read(&self) -> bool {
- let r = libc::pthread_rwlock_tryrdlock(self.inner.get());
+ pub fn try_read(&self) -> bool {
+ let lock = &*self.inner;
+ let r = unsafe { libc::pthread_rwlock_tryrdlock(lock.inner.get()) };
if r == 0 {
- if *self.write_locked.get() {
+ if unsafe { *lock.write_locked.get() } {
// `pthread_rwlock_tryrdlock` succeeded when it should not have.
- self.raw_unlock();
+ unsafe {
+ lock.raw_unlock();
+ }
false
} else {
- self.num_readers.fetch_add(1, Ordering::Relaxed);
+ lock.num_readers.fetch_add(1, Ordering::Relaxed);
true
}
} else {
false
}
}
+
#[inline]
- pub unsafe fn write(&self) {
- let r = libc::pthread_rwlock_wrlock(self.inner.get());
+ pub fn write(&self) {
+ let lock = &*self.inner;
+ let r = unsafe { libc::pthread_rwlock_wrlock(lock.inner.get()) };
// See comments above for why we check for EDEADLK and write_locked. For the same reason,
// we also need to check that there are no readers (tracked in `num_readers`).
if r == libc::EDEADLK
- || (r == 0 && *self.write_locked.get())
- || self.num_readers.load(Ordering::Relaxed) != 0
+ || (r == 0 && unsafe { *lock.write_locked.get() })
+ || lock.num_readers.load(Ordering::Relaxed) != 0
{
// Above, we make sure to only access `write_locked` when `r == 0` to avoid
// data races.
if r == 0 {
// `pthread_rwlock_wrlock` succeeded when it should not have.
- self.raw_unlock();
+ unsafe {
+ lock.raw_unlock();
+ }
}
panic!("rwlock write lock would result in deadlock");
} else {
// return EDEADLK or 0. We rely on that.
debug_assert_eq!(r, 0);
}
- *self.write_locked.get() = true;
+
+ unsafe {
+ *lock.write_locked.get() = true;
+ }
}
+
#[inline]
pub unsafe fn try_write(&self) -> bool {
- let r = libc::pthread_rwlock_trywrlock(self.inner.get());
+ let lock = &*self.inner;
+ let r = libc::pthread_rwlock_trywrlock(lock.inner.get());
if r == 0 {
- if *self.write_locked.get() || self.num_readers.load(Ordering::Relaxed) != 0 {
+ if *lock.write_locked.get() || lock.num_readers.load(Ordering::Relaxed) != 0 {
// `pthread_rwlock_trywrlock` succeeded when it should not have.
- self.raw_unlock();
+ lock.raw_unlock();
false
} else {
- *self.write_locked.get() = true;
+ *lock.write_locked.get() = true;
true
}
} else {
false
}
}
- #[inline]
- unsafe fn raw_unlock(&self) {
- let r = libc::pthread_rwlock_unlock(self.inner.get());
- debug_assert_eq!(r, 0);
- }
+
#[inline]
pub unsafe fn read_unlock(&self) {
- debug_assert!(!*self.write_locked.get());
- self.num_readers.fetch_sub(1, Ordering::Relaxed);
- self.raw_unlock();
- }
- #[inline]
- pub unsafe fn write_unlock(&self) {
- debug_assert_eq!(self.num_readers.load(Ordering::Relaxed), 0);
- debug_assert!(*self.write_locked.get());
- *self.write_locked.get() = false;
- self.raw_unlock();
+ let lock = &*self.inner;
+ debug_assert!(!*lock.write_locked.get());
+ lock.num_readers.fetch_sub(1, Ordering::Relaxed);
+ lock.raw_unlock();
}
- #[inline]
- unsafe fn destroy(&mut self) {
- let r = libc::pthread_rwlock_destroy(self.inner.get());
- // On DragonFly pthread_rwlock_destroy() returns EINVAL if called on a
- // rwlock that was just initialized with
- // libc::PTHREAD_RWLOCK_INITIALIZER. Once it is used (locked/unlocked)
- // or pthread_rwlock_init() is called, this behaviour no longer occurs.
- if cfg!(target_os = "dragonfly") {
- debug_assert!(r == 0 || r == libc::EINVAL);
- } else {
- debug_assert_eq!(r, 0);
- }
- }
-}
-impl Drop for RwLock {
#[inline]
- fn drop(&mut self) {
- unsafe { self.destroy() };
+ pub unsafe fn write_unlock(&self) {
+ let lock = &*self.inner;
+ debug_assert_eq!(lock.num_readers.load(Ordering::Relaxed), 0);
+ debug_assert!(*lock.write_locked.get());
+ *lock.write_locked.get() = false;
+ lock.raw_unlock();
}
}
projects / rust.git / blobdiff