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rwlock.rs
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rwlock.rs
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use prelude::v1::*;
use cell::UnsafeCell;
use fmt;
use marker;
use mem;
use ops::{Deref, DerefMut};
use ptr;
use sys_common::poison::{self, LockResult, TryLockError, TryLockResult};
use sys_common::rwlock as sys;
/// A reader-writer lock
///
/// This type of lock allows a number of readers or at most one writer at any
/// point in time. The write portion of this lock typically allows modification
/// of the underlying data (exclusive access) and the read portion of this lock
/// typically allows for read-only access (shared access).
///
/// The priority policy of the lock is dependent on the underlying operating
/// system's implementation, and this type does not guarantee that any
/// particular policy will be used.
///
/// The type parameter `T` represents the data that this lock protects. It is
/// required that `T` satisfies `Send` to be shared across threads and `Sync` to
/// allow concurrent access through readers. The RAII guards returned from the
/// locking methods implement `Deref` (and `DerefMut` for the `write` methods)
/// to allow access to the contained of the lock.
///
/// # Poisoning
///
/// An `RwLock`, like `Mutex`, will become poisoned on a panic. Note, however,
/// that an `RwLock` may only be poisoned if a panic occurs while it is locked
/// exclusively (write mode). If a panic occurs in any reader, then the lock
/// will not be poisoned.
///
/// # Examples
///
/// ```
/// use std::sync::RwLock;
///
/// let lock = RwLock::new(5);
///
/// // many reader locks can be held at once
/// {
/// let r1 = lock.read().unwrap();
/// let r2 = lock.read().unwrap();
/// assert_eq!(*r1, 5);
/// assert_eq!(*r2, 5);
/// } // read locks are dropped at this point
///
/// // only one write lock may be held, however
/// {
/// let mut w = lock.write().unwrap();
/// *w += 1;
/// assert_eq!(*w, 6);
/// } // write lock is dropped here
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
pub struct RwLock<T: ?Sized> {
inner: Box<StaticRwLock>,
data: UnsafeCell<T>,
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: ?Sized + Send + Sync> Send for RwLock<T> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
/// Structure representing a statically allocated RwLock.
///
/// This structure is intended to be used inside of a `static` and will provide
/// automatic global access as well as lazy initialization. The internal
/// resources of this RwLock, however, must be manually deallocated.
///
/// # Examples
///
/// ```
/// #![feature(static_rwlock)]
///
/// use std::sync::{StaticRwLock, RW_LOCK_INIT};
///
/// static LOCK: StaticRwLock = RW_LOCK_INIT;
///
/// {
/// let _g = LOCK.read().unwrap();
/// // ... shared read access
/// }
/// {
/// let _g = LOCK.write().unwrap();
/// // ... exclusive write access
/// }
/// unsafe { LOCK.destroy() } // free all resources
/// ```
#[unstable(feature = "static_rwlock",
reason = "may be merged with RwLock in the future",
issue = "27717")]
#[rustc_deprecated(since = "1.10.0",
reason = "the lazy-static crate suffices for static sync \
primitives and eventually this type shouldn't \
be necessary as `RwLock::new` in a static should \
suffice")]
pub struct StaticRwLock {
lock: sys::RWLock,
poison: poison::Flag,
}
/// Constant initialization for a statically-initialized rwlock.
#[unstable(feature = "static_rwlock",
reason = "may be merged with RwLock in the future",
issue = "27717")]
#[rustc_deprecated(since = "1.10.0",
reason = "the lazy-static crate suffices for static sync \
primitives and eventually this type shouldn't \
be necessary as `RwLock::new` in a static should \
suffice")]
#[allow(deprecated)]
pub const RW_LOCK_INIT: StaticRwLock = StaticRwLock::new();
/// RAII structure used to release the shared read access of a lock when
/// dropped.
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
__lock: &'a StaticRwLock,
__data: &'a T,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> !marker::Send for RwLockReadGuard<'a, T> {}
/// RAII structure used to release the exclusive write access of a lock when
/// dropped.
#[must_use]
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
__lock: &'a StaticRwLock,
__data: &'a mut T,
__poison: poison::Guard,
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> !marker::Send for RwLockWriteGuard<'a, T> {}
#[allow(deprecated)]
impl<T> RwLock<T> {
/// Creates a new instance of an `RwLock<T>` which is unlocked.
///
/// # Examples
///
/// ```
/// use std::sync::RwLock;
///
/// let lock = RwLock::new(5);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(t: T) -> RwLock<T> {
RwLock { inner: box StaticRwLock::new(), data: UnsafeCell::new(t) }
}
}
#[allow(deprecated)]
impl<T: ?Sized> RwLock<T> {
/// Locks this rwlock with shared read access, blocking the current thread
/// until it can be acquired.
///
/// The calling thread will be blocked until there are no more writers which
/// hold the lock. There may be other readers currently inside the lock when
/// this method returns. This method does not provide any guarantees with
/// respect to the ordering of whether contentious readers or writers will
/// acquire the lock first.
///
/// Returns an RAII guard which will release this thread's shared access
/// once it is dropped.
///
/// # Errors
///
/// This function will return an error if the RwLock is poisoned. An RwLock
/// is poisoned whenever a writer panics while holding an exclusive lock.
/// The failure will occur immediately after the lock has been acquired.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn read(&self) -> LockResult<RwLockReadGuard<T>> {
unsafe {
self.inner.lock.read();
RwLockReadGuard::new(&*self.inner, &self.data)
}
}
/// Attempts to acquire this rwlock with shared read access.
///
/// If the access could not be granted at this time, then `Err` is returned.
/// Otherwise, an RAII guard is returned which will release the shared access
/// when it is dropped.
///
/// This function does not block.
///
/// This function does not provide any guarantees with respect to the ordering
/// of whether contentious readers or writers will acquire the lock first.
///
/// # Errors
///
/// This function will return an error if the RwLock is poisoned. An RwLock
/// is poisoned whenever a writer panics while holding an exclusive lock. An
/// error will only be returned if the lock would have otherwise been
/// acquired.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn try_read(&self) -> TryLockResult<RwLockReadGuard<T>> {
unsafe {
if self.inner.lock.try_read() {
Ok(RwLockReadGuard::new(&*self.inner, &self.data)?)
} else {
Err(TryLockError::WouldBlock)
}
}
}
/// Locks this rwlock with exclusive write access, blocking the current
/// thread until it can be acquired.
///
/// This function will not return while other writers or other readers
/// currently have access to the lock.
///
/// Returns an RAII guard which will drop the write access of this rwlock
/// when dropped.
///
/// # Errors
///
/// This function will return an error if the RwLock is poisoned. An RwLock
/// is poisoned whenever a writer panics while holding an exclusive lock.
/// An error will be returned when the lock is acquired.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn write(&self) -> LockResult<RwLockWriteGuard<T>> {
unsafe {
self.inner.lock.write();
RwLockWriteGuard::new(&*self.inner, &self.data)
}
}
/// Attempts to lock this rwlock with exclusive write access.
///
/// If the lock could not be acquired at this time, then `Err` is returned.
/// Otherwise, an RAII guard is returned which will release the lock when
/// it is dropped.
///
/// This function does not block.
///
/// This function does not provide any guarantees with respect to the ordering
/// of whether contentious readers or writers will acquire the lock first.
///
/// # Errors
///
/// This function will return an error if the RwLock is poisoned. An RwLock
/// is poisoned whenever a writer panics while holding an exclusive lock. An
/// error will only be returned if the lock would have otherwise been
/// acquired.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn try_write(&self) -> TryLockResult<RwLockWriteGuard<T>> {
unsafe {
if self.inner.lock.try_write() {
Ok(RwLockWriteGuard::new(&*self.inner, &self.data)?)
} else {
Err(TryLockError::WouldBlock)
}
}
}
/// Determines whether the lock is poisoned.
///
/// If another thread is active, the lock can still become poisoned at any
/// time. You should not trust a `false` value for program correctness
/// without additional synchronization.
#[inline]
#[stable(feature = "sync_poison", since = "1.2.0")]
pub fn is_poisoned(&self) -> bool {
self.inner.poison.get()
}
/// Consumes this `RwLock`, returning the underlying data.
///
/// # Errors
///
/// This function will return an error if the RwLock is poisoned. An RwLock
/// is poisoned whenever a writer panics while holding an exclusive lock. An
/// error will only be returned if the lock would have otherwise been
/// acquired.
#[stable(feature = "rwlock_into_inner", since = "1.6.0")]
pub fn into_inner(self) -> LockResult<T> where T: Sized {
// We know statically that there are no outstanding references to
// `self` so there's no need to lock the inner StaticRwLock.
//
// To get the inner value, we'd like to call `data.into_inner()`,
// but because `RwLock` impl-s `Drop`, we can't move out of it, so
// we'll have to destructure it manually instead.
unsafe {
// Like `let RwLock { inner, data } = self`.
let (inner, data) = {
let RwLock { ref inner, ref data } = self;
(ptr::read(inner), ptr::read(data))
};
mem::forget(self);
inner.lock.destroy(); // Keep in sync with the `Drop` impl.
poison::map_result(inner.poison.borrow(), |_| data.into_inner())
}
}
/// Returns a mutable reference to the underlying data.
///
/// Since this call borrows the `RwLock` mutably, no actual locking needs to
/// take place---the mutable borrow statically guarantees no locks exist.
///
/// # Errors
///
/// This function will return an error if the RwLock is poisoned. An RwLock
/// is poisoned whenever a writer panics while holding an exclusive lock. An
/// error will only be returned if the lock would have otherwise been
/// acquired.
#[stable(feature = "rwlock_get_mut", since = "1.6.0")]
pub fn get_mut(&mut self) -> LockResult<&mut T> {
// We know statically that there are no other references to `self`, so
// there's no need to lock the inner StaticRwLock.
let data = unsafe { &mut *self.data.get() };
poison::map_result(self.inner.poison.borrow(), |_| data )
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[allow(deprecated)]
impl<T: ?Sized> Drop for RwLock<T> {
#[unsafe_destructor_blind_to_params]
fn drop(&mut self) {
// IMPORTANT: This code needs to be kept in sync with `RwLock::into_inner`.
unsafe { self.inner.lock.destroy() }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized + fmt::Debug> fmt::Debug for RwLock<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.try_read() {
Ok(guard) => write!(f, "RwLock {{ data: {:?} }}", &*guard),
Err(TryLockError::Poisoned(err)) => {
write!(f, "RwLock {{ data: Poisoned({:?}) }}", &**err.get_ref())
},
Err(TryLockError::WouldBlock) => write!(f, "RwLock {{ <locked> }}")
}
}
}
#[stable(feature = "rw_lock_default", since = "1.9.0")]
impl<T: Default> Default for RwLock<T> {
fn default() -> RwLock<T> {
RwLock::new(Default::default())
}
}
struct Dummy(UnsafeCell<()>);
unsafe impl Sync for Dummy {}
static DUMMY: Dummy = Dummy(UnsafeCell::new(()));
#[unstable(feature = "static_rwlock",
reason = "may be merged with RwLock in the future",
issue = "27717")]
#[rustc_deprecated(since = "1.10.0",
reason = "the lazy-static crate suffices for static sync \
primitives and eventually this type shouldn't \
be necessary as `RwLock::new` in a static should \
suffice")]
#[allow(deprecated)]
impl StaticRwLock {
/// Creates a new rwlock.
pub const fn new() -> StaticRwLock {
StaticRwLock {
lock: sys::RWLock::new(),
poison: poison::Flag::new(),
}
}
/// Locks this rwlock with shared read access, blocking the current thread
/// until it can be acquired.
///
/// See `RwLock::read`.
#[inline]
pub fn read(&'static self) -> LockResult<RwLockReadGuard<'static, ()>> {
unsafe {
self.lock.read();
RwLockReadGuard::new(self, &DUMMY.0)
}
}
/// Attempts to acquire this lock with shared read access.
///
/// See `RwLock::try_read`.
#[inline]
pub fn try_read(&'static self)
-> TryLockResult<RwLockReadGuard<'static, ()>> {
unsafe {
if self.lock.try_read(){
Ok(RwLockReadGuard::new(self, &DUMMY.0)?)
} else {
Err(TryLockError::WouldBlock)
}
}
}
/// Locks this rwlock with exclusive write access, blocking the current
/// thread until it can be acquired.
///
/// See `RwLock::write`.
#[inline]
pub fn write(&'static self) -> LockResult<RwLockWriteGuard<'static, ()>> {
unsafe {
self.lock.write();
RwLockWriteGuard::new(self, &DUMMY.0)
}
}
/// Attempts to lock this rwlock with exclusive write access.
///
/// See `RwLock::try_write`.
#[inline]
pub fn try_write(&'static self)
-> TryLockResult<RwLockWriteGuard<'static, ()>> {
unsafe {
if self.lock.try_write() {
Ok(RwLockWriteGuard::new(self, &DUMMY.0)?)
} else {
Err(TryLockError::WouldBlock)
}
}
}
/// Deallocates all resources associated with this static lock.
///
/// This method is unsafe to call as there is no guarantee that there are no
/// active users of the lock, and this also doesn't prevent any future users
/// of this lock. This method is required to be called to not leak memory on
/// all platforms.
pub unsafe fn destroy(&'static self) {
self.lock.destroy()
}
}
#[allow(deprecated)]
impl<'rwlock, T: ?Sized> RwLockReadGuard<'rwlock, T> {
unsafe fn new(lock: &'rwlock StaticRwLock, data: &'rwlock UnsafeCell<T>)
-> LockResult<RwLockReadGuard<'rwlock, T>> {
poison::map_result(lock.poison.borrow(), |_| {
RwLockReadGuard {
__lock: lock,
__data: &*data.get(),
}
})
}
/// Transform this guard to hold a sub-borrow of the original data.
///
/// Applies the supplied closure to the data, returning a new lock
/// guard referencing the borrow returned by the closure.
///
/// # Examples
///
/// ```rust
/// # #![feature(guard_map)]
/// # use std::sync::{RwLockReadGuard, RwLock};
/// let x = RwLock::new(vec![1, 2]);
///
/// let y = RwLockReadGuard::map(x.read().unwrap(), |v| &v[0]);
/// assert_eq!(*y, 1);
/// ```
#[unstable(feature = "guard_map",
reason = "recently added, needs RFC for stabilization,
questionable interaction with Condvar",
issue = "27746")]
#[rustc_deprecated(since = "1.8.0",
reason = "unsound on Mutex because of Condvar and \
RwLock may also with to be used with Condvar \
one day")]
pub fn map<U: ?Sized, F>(this: Self, cb: F) -> RwLockReadGuard<'rwlock, U>
where F: FnOnce(&T) -> &U
{
let new = RwLockReadGuard {
__lock: this.__lock,
__data: cb(this.__data)
};
mem::forget(this);
new
}
}
#[allow(deprecated)]
impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
unsafe fn new(lock: &'rwlock StaticRwLock, data: &'rwlock UnsafeCell<T>)
-> LockResult<RwLockWriteGuard<'rwlock, T>> {
poison::map_result(lock.poison.borrow(), |guard| {
RwLockWriteGuard {
__lock: lock,
__data: &mut *data.get(),
__poison: guard,
}
})
}
/// Transform this guard to hold a sub-borrow of the original data.
///
/// Applies the supplied closure to the data, returning a new lock
/// guard referencing the borrow returned by the closure.
///
/// # Examples
///
/// ```rust
/// # #![feature(guard_map)]
/// # use std::sync::{RwLockWriteGuard, RwLock};
/// let x = RwLock::new(vec![1, 2]);
///
/// {
/// let mut y = RwLockWriteGuard::map(x.write().unwrap(), |v| &mut v[0]);
/// assert_eq!(*y, 1);
///
/// *y = 10;
/// }
///
/// assert_eq!(&**x.read().unwrap(), &[10, 2]);
/// ```
#[unstable(feature = "guard_map",
reason = "recently added, needs RFC for stabilization,
questionable interaction with Condvar",
issue = "27746")]
#[rustc_deprecated(since = "1.8.0",
reason = "unsound on Mutex because of Condvar and \
RwLock may also with to be used with Condvar \
one day")]
pub fn map<U: ?Sized, F>(this: Self, cb: F) -> RwLockWriteGuard<'rwlock, U>
where F: FnOnce(&mut T) -> &mut U
{
// Compute the new data while still owning the original lock
// in order to correctly poison if the callback panics.
let data = unsafe { ptr::read(&this.__data) };
let new_data = cb(data);
// We don't want to unlock the lock by running the destructor of the
// original lock, so just read the fields we need and forget it.
let (poison, lock) = unsafe {
(ptr::read(&this.__poison), ptr::read(&this.__lock))
};
mem::forget(this);
RwLockWriteGuard {
__lock: lock,
__data: new_data,
__poison: poison
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'rwlock, T: ?Sized> Deref for RwLockReadGuard<'rwlock, T> {
type Target = T;
fn deref(&self) -> &T { self.__data }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'rwlock, T: ?Sized> Deref for RwLockWriteGuard<'rwlock, T> {
type Target = T;
fn deref(&self) -> &T { self.__data }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'rwlock, T: ?Sized> DerefMut for RwLockWriteGuard<'rwlock, T> {
fn deref_mut(&mut self) -> &mut T {
self.__data
}
}
#[allow(deprecated)]
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> Drop for RwLockReadGuard<'a, T> {
fn drop(&mut self) {
unsafe { self.__lock.lock.read_unlock(); }
}
}
#[allow(deprecated)]
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T: ?Sized> Drop for RwLockWriteGuard<'a, T> {
fn drop(&mut self) {
self.__lock.poison.done(&self.__poison);
unsafe { self.__lock.lock.write_unlock(); }
}
}
#[cfg(test)]
#[allow(deprecated)]
mod tests {
#![allow(deprecated)] // rand
use prelude::v1::*;
use rand::{self, Rng};
use sync::mpsc::channel;
use thread;
use sync::{Arc, RwLock, StaticRwLock, TryLockError, RwLockWriteGuard};
use sync::atomic::{AtomicUsize, Ordering};
#[derive(Eq, PartialEq, Debug)]
struct NonCopy(i32);
#[test]
fn smoke() {
let l = RwLock::new(());
drop(l.read().unwrap());
drop(l.write().unwrap());
drop((l.read().unwrap(), l.read().unwrap()));
drop(l.write().unwrap());
}
#[test]
fn static_smoke() {
static R: StaticRwLock = StaticRwLock::new();
drop(R.read().unwrap());
drop(R.write().unwrap());
drop((R.read().unwrap(), R.read().unwrap()));
drop(R.write().unwrap());
unsafe { R.destroy(); }
}
#[test]
fn frob() {
static R: StaticRwLock = StaticRwLock::new();
const N: usize = 10;
const M: usize = 1000;
let (tx, rx) = channel::<()>();
for _ in 0..N {
let tx = tx.clone();
thread::spawn(move|| {
let mut rng = rand::thread_rng();
for _ in 0..M {
if rng.gen_weighted_bool(N) {
drop(R.write().unwrap());
} else {
drop(R.read().unwrap());
}
}
drop(tx);
});
}
drop(tx);
let _ = rx.recv();
unsafe { R.destroy(); }
}
#[test]
fn test_rw_arc_poison_wr() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move|| {
let _lock = arc2.write().unwrap();
panic!();
}).join();
assert!(arc.read().is_err());
}
#[test]
fn test_rw_arc_poison_ww() {
let arc = Arc::new(RwLock::new(1));
assert!(!arc.is_poisoned());
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move|| {
let _lock = arc2.write().unwrap();
panic!();
}).join();
assert!(arc.write().is_err());
assert!(arc.is_poisoned());
}
#[test]
fn test_rw_arc_no_poison_rr() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move|| {
let _lock = arc2.read().unwrap();
panic!();
}).join();
let lock = arc.read().unwrap();
assert_eq!(*lock, 1);
}
#[test]
fn test_rw_arc_no_poison_rw() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _: Result<(), _> = thread::spawn(move|| {
let _lock = arc2.read().unwrap();
panic!()
}).join();
let lock = arc.write().unwrap();
assert_eq!(*lock, 1);
}
#[test]
fn test_rw_arc() {
let arc = Arc::new(RwLock::new(0));
let arc2 = arc.clone();
let (tx, rx) = channel();
thread::spawn(move|| {
let mut lock = arc2.write().unwrap();
for _ in 0..10 {
let tmp = *lock;
*lock = -1;
thread::yield_now();
*lock = tmp + 1;
}
tx.send(()).unwrap();
});
// Readers try to catch the writer in the act
let mut children = Vec::new();
for _ in 0..5 {
let arc3 = arc.clone();
children.push(thread::spawn(move|| {
let lock = arc3.read().unwrap();
assert!(*lock >= 0);
}));
}
// Wait for children to pass their asserts
for r in children {
assert!(r.join().is_ok());
}
// Wait for writer to finish
rx.recv().unwrap();
let lock = arc.read().unwrap();
assert_eq!(*lock, 10);
}
#[test]
fn test_rw_arc_access_in_unwind() {
let arc = Arc::new(RwLock::new(1));
let arc2 = arc.clone();
let _ = thread::spawn(move|| -> () {
struct Unwinder {
i: Arc<RwLock<isize>>,
}
impl Drop for Unwinder {
fn drop(&mut self) {
let mut lock = self.i.write().unwrap();
*lock += 1;
}
}
let _u = Unwinder { i: arc2 };
panic!();
}).join();
let lock = arc.read().unwrap();
assert_eq!(*lock, 2);
}
#[test]
fn test_rwlock_unsized() {
let rw: &RwLock<[i32]> = &RwLock::new([1, 2, 3]);
{
let b = &mut *rw.write().unwrap();
b[0] = 4;
b[2] = 5;
}
let comp: &[i32] = &[4, 2, 5];
assert_eq!(&*rw.read().unwrap(), comp);
}
#[test]
fn test_rwlock_try_write() {
use mem::drop;
let lock = RwLock::new(0isize);
let read_guard = lock.read().unwrap();
let write_result = lock.try_write();
match write_result {
Err(TryLockError::WouldBlock) => (),
Ok(_) => assert!(false, "try_write should not succeed while read_guard is in scope"),
Err(_) => assert!(false, "unexpected error"),
}
drop(read_guard);
}
#[test]
fn test_into_inner() {
let m = RwLock::new(NonCopy(10));
assert_eq!(m.into_inner().unwrap(), NonCopy(10));
}
#[test]
fn test_into_inner_drop() {
struct Foo(Arc<AtomicUsize>);
impl Drop for Foo {
fn drop(&mut self) {
self.0.fetch_add(1, Ordering::SeqCst);
}
}
let num_drops = Arc::new(AtomicUsize::new(0));
let m = RwLock::new(Foo(num_drops.clone()));
assert_eq!(num_drops.load(Ordering::SeqCst), 0);
{
let _inner = m.into_inner().unwrap();
assert_eq!(num_drops.load(Ordering::SeqCst), 0);
}
assert_eq!(num_drops.load(Ordering::SeqCst), 1);
}
#[test]
fn test_into_inner_poison() {
let m = Arc::new(RwLock::new(NonCopy(10)));
let m2 = m.clone();
let _ = thread::spawn(move || {
let _lock = m2.write().unwrap();
panic!("test panic in inner thread to poison RwLock");
}).join();
assert!(m.is_poisoned());
match Arc::try_unwrap(m).unwrap().into_inner() {
Err(e) => assert_eq!(e.into_inner(), NonCopy(10)),
Ok(x) => panic!("into_inner of poisoned RwLock is Ok: {:?}", x),
}
}
#[test]
fn test_get_mut() {
let mut m = RwLock::new(NonCopy(10));
*m.get_mut().unwrap() = NonCopy(20);
assert_eq!(m.into_inner().unwrap(), NonCopy(20));
}
#[test]
fn test_get_mut_poison() {
let m = Arc::new(RwLock::new(NonCopy(10)));
let m2 = m.clone();
let _ = thread::spawn(move || {
let _lock = m2.write().unwrap();
panic!("test panic in inner thread to poison RwLock");
}).join();
assert!(m.is_poisoned());
match Arc::try_unwrap(m).unwrap().get_mut() {
Err(e) => assert_eq!(*e.into_inner(), NonCopy(10)),
Ok(x) => panic!("get_mut of poisoned RwLock is Ok: {:?}", x),
}
}
#[test]
fn test_rwlock_write_map_poison() {
let rwlock = Arc::new(RwLock::new(vec![1, 2]));
let rwlock2 = rwlock.clone();
thread::spawn(move || {
let _ = RwLockWriteGuard::map::<usize, _>(rwlock2.write().unwrap(), |_| panic!());
}).join().unwrap_err();
match rwlock.read() {
Ok(r) => panic!("Read lock on poisioned RwLock is Ok: {:?}", &*r),
Err(_) => {}
};
}
}