768 lines
24 KiB
Rust
768 lines
24 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/**
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* Concurrency-enabled mechanisms for sharing mutable and/or immutable state
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* between tasks.
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*/
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use sync;
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use sync::{Mutex, mutex_with_condvars, RWlock, rwlock_with_condvars};
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use core::cast;
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use core::unstable::{SharedMutableState, shared_mutable_state};
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use core::unstable::{clone_shared_mutable_state};
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use core::unstable::{get_shared_mutable_state, get_shared_immutable_state};
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use core::ptr;
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use core::task;
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/// As sync::condvar, a mechanism for unlock-and-descheduling and signalling.
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pub struct Condvar<'self> {
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is_mutex: bool,
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failed: &'self mut bool,
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cond: &'self sync::Condvar<'self>
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}
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pub impl<'self> Condvar<'self> {
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/// Atomically exit the associated ARC and block until a signal is sent.
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#[inline(always)]
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fn wait(&self) { self.wait_on(0) }
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/**
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* Atomically exit the associated ARC and block on a specified condvar
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* until a signal is sent on that same condvar (as sync::cond.wait_on).
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*
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* wait() is equivalent to wait_on(0).
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*/
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#[inline(always)]
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fn wait_on(&self, condvar_id: uint) {
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assert!(!*self.failed);
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self.cond.wait_on(condvar_id);
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// This is why we need to wrap sync::condvar.
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check_poison(self.is_mutex, *self.failed);
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}
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/// Wake up a blocked task. Returns false if there was no blocked task.
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#[inline(always)]
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fn signal(&self) -> bool { self.signal_on(0) }
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/**
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* Wake up a blocked task on a specified condvar (as
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* sync::cond.signal_on). Returns false if there was no blocked task.
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*/
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#[inline(always)]
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fn signal_on(&self, condvar_id: uint) -> bool {
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assert!(!*self.failed);
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self.cond.signal_on(condvar_id)
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}
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/// Wake up all blocked tasks. Returns the number of tasks woken.
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#[inline(always)]
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fn broadcast(&self) -> uint { self.broadcast_on(0) }
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/**
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* Wake up all blocked tasks on a specified condvar (as
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* sync::cond.broadcast_on). Returns Returns the number of tasks woken.
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*/
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#[inline(always)]
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fn broadcast_on(&self, condvar_id: uint) -> uint {
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assert!(!*self.failed);
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self.cond.broadcast_on(condvar_id)
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}
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}
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/****************************************************************************
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* Immutable ARC
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****************************************************************************/
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/// An atomically reference counted wrapper for shared immutable state.
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struct ARC<T> { x: SharedMutableState<T> }
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/// Create an atomically reference counted wrapper.
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pub fn ARC<T:Const + Owned>(data: T) -> ARC<T> {
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ARC { x: unsafe { shared_mutable_state(data) } }
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}
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/**
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* Access the underlying data in an atomically reference counted
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* wrapper.
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*/
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pub fn get<'a, T:Const + Owned>(rc: &'a ARC<T>) -> &'a T {
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unsafe { get_shared_immutable_state(&rc.x) }
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}
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/**
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* Duplicate an atomically reference counted wrapper.
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*
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* The resulting two `arc` objects will point to the same underlying data
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* object. However, one of the `arc` objects can be sent to another task,
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* allowing them to share the underlying data.
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*/
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pub fn clone<T:Const + Owned>(rc: &ARC<T>) -> ARC<T> {
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ARC { x: unsafe { clone_shared_mutable_state(&rc.x) } }
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}
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impl<T:Const + Owned> Clone for ARC<T> {
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fn clone(&self) -> ARC<T> {
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clone(self)
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}
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}
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/****************************************************************************
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* Mutex protected ARC (unsafe)
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****************************************************************************/
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#[doc(hidden)]
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struct MutexARCInner<T> { lock: Mutex, failed: bool, data: T }
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/// An ARC with mutable data protected by a blocking mutex.
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struct MutexARC<T> { x: SharedMutableState<MutexARCInner<T>> }
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/// Create a mutex-protected ARC with the supplied data.
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pub fn MutexARC<T:Owned>(user_data: T) -> MutexARC<T> {
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mutex_arc_with_condvars(user_data, 1)
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}
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/**
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* Create a mutex-protected ARC with the supplied data and a specified number
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* of condvars (as sync::mutex_with_condvars).
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*/
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pub fn mutex_arc_with_condvars<T:Owned>(user_data: T,
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num_condvars: uint) -> MutexARC<T> {
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let data =
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MutexARCInner { lock: mutex_with_condvars(num_condvars),
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failed: false, data: user_data };
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MutexARC { x: unsafe { shared_mutable_state(data) } }
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}
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impl<T:Owned> Clone for MutexARC<T> {
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/// Duplicate a mutex-protected ARC, as arc::clone.
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fn clone(&self) -> MutexARC<T> {
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// NB: Cloning the underlying mutex is not necessary. Its reference
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// count would be exactly the same as the shared state's.
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MutexARC { x: unsafe { clone_shared_mutable_state(&self.x) } }
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}
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}
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pub impl<T:Owned> MutexARC<T> {
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/**
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* Access the underlying mutable data with mutual exclusion from other
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* tasks. The argument closure will be run with the mutex locked; all
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* other tasks wishing to access the data will block until the closure
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* finishes running.
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*
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* The reason this function is 'unsafe' is because it is possible to
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* construct a circular reference among multiple ARCs by mutating the
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* underlying data. This creates potential for deadlock, but worse, this
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* will guarantee a memory leak of all involved ARCs. Using mutex ARCs
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* inside of other ARCs is safe in absence of circular references.
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*
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* If you wish to nest mutex_arcs, one strategy for ensuring safety at
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* runtime is to add a "nesting level counter" inside the stored data, and
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* when traversing the arcs, assert that they monotonically decrease.
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*
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* # Failure
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*
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* Failing while inside the ARC will unlock the ARC while unwinding, so
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* that other tasks won't block forever. It will also poison the ARC:
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* any tasks that subsequently try to access it (including those already
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* blocked on the mutex) will also fail immediately.
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*/
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#[inline(always)]
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unsafe fn access<U>(&self, blk: &fn(x: &mut T) -> U) -> U {
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let state = get_shared_mutable_state(&self.x);
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// Borrowck would complain about this if the function were
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// not already unsafe. See borrow_rwlock, far below.
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do (&(*state).lock).lock {
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check_poison(true, (*state).failed);
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let _z = PoisonOnFail(&mut (*state).failed);
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blk(&mut (*state).data)
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}
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}
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/// As access(), but with a condvar, as sync::mutex.lock_cond().
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#[inline(always)]
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unsafe fn access_cond<'x, 'c, U>(
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&self,
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blk: &fn(x: &'x mut T, c: &'c Condvar) -> U) -> U
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{
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let state = get_shared_mutable_state(&self.x);
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do (&(*state).lock).lock_cond |cond| {
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check_poison(true, (*state).failed);
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let _z = PoisonOnFail(&mut (*state).failed);
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blk(&mut (*state).data,
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&Condvar {is_mutex: true,
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failed: &mut (*state).failed,
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cond: cond })
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}
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}
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}
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// Common code for {mutex.access,rwlock.write}{,_cond}.
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#[inline(always)]
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#[doc(hidden)]
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fn check_poison(is_mutex: bool, failed: bool) {
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if failed {
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if is_mutex {
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fail!(~"Poisoned MutexARC - another task failed inside!");
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} else {
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fail!(~"Poisoned rw_arc - another task failed inside!");
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}
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}
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}
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#[doc(hidden)]
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struct PoisonOnFail {
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failed: *mut bool,
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}
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impl Drop for PoisonOnFail {
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fn finalize(&self) {
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unsafe {
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/* assert!(!*self.failed);
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-- might be false in case of cond.wait() */
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if task::failing() {
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*self.failed = true;
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}
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}
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}
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}
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fn PoisonOnFail<'r>(failed: &'r mut bool) -> PoisonOnFail {
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PoisonOnFail {
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failed: ptr::to_mut_unsafe_ptr(failed)
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}
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}
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/****************************************************************************
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* R/W lock protected ARC
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****************************************************************************/
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#[doc(hidden)]
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struct RWARCInner<T> { lock: RWlock, failed: bool, data: T }
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/**
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* A dual-mode ARC protected by a reader-writer lock. The data can be accessed
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* mutably or immutably, and immutably-accessing tasks may run concurrently.
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*
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* Unlike mutex_arcs, rw_arcs are safe, because they cannot be nested.
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*/
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#[mutable]
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struct RWARC<T> {
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x: SharedMutableState<RWARCInner<T>>,
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cant_nest: ()
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}
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/// Create a reader/writer ARC with the supplied data.
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pub fn RWARC<T:Const + Owned>(user_data: T) -> RWARC<T> {
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rw_arc_with_condvars(user_data, 1)
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}
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/**
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* Create a reader/writer ARC with the supplied data and a specified number
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* of condvars (as sync::rwlock_with_condvars).
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*/
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pub fn rw_arc_with_condvars<T:Const + Owned>(
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user_data: T,
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num_condvars: uint) -> RWARC<T>
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{
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let data =
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RWARCInner { lock: rwlock_with_condvars(num_condvars),
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failed: false, data: user_data };
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RWARC { x: unsafe { shared_mutable_state(data) }, cant_nest: () }
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}
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pub impl<T:Const + Owned> RWARC<T> {
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/// Duplicate a rwlock-protected ARC, as arc::clone.
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fn clone(&self) -> RWARC<T> {
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RWARC { x: unsafe { clone_shared_mutable_state(&self.x) },
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cant_nest: () }
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}
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}
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pub impl<T:Const + Owned> RWARC<T> {
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/**
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* Access the underlying data mutably. Locks the rwlock in write mode;
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* other readers and writers will block.
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*
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* # Failure
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*
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* Failing while inside the ARC will unlock the ARC while unwinding, so
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* that other tasks won't block forever. As MutexARC.access, it will also
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* poison the ARC, so subsequent readers and writers will both also fail.
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*/
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#[inline(always)]
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fn write<U>(&self, blk: &fn(x: &mut T) -> U) -> U {
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unsafe {
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let state = get_shared_mutable_state(&self.x);
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do (*borrow_rwlock(state)).write {
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check_poison(false, (*state).failed);
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let _z = PoisonOnFail(&mut (*state).failed);
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blk(&mut (*state).data)
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}
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}
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}
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/// As write(), but with a condvar, as sync::rwlock.write_cond().
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#[inline(always)]
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fn write_cond<'x, 'c, U>(&self,
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blk: &fn(x: &'x mut T, c: &'c Condvar) -> U)
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-> U {
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unsafe {
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let state = get_shared_mutable_state(&self.x);
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do (*borrow_rwlock(state)).write_cond |cond| {
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check_poison(false, (*state).failed);
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let _z = PoisonOnFail(&mut (*state).failed);
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blk(&mut (*state).data,
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&Condvar {is_mutex: false,
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failed: &mut (*state).failed,
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cond: cond})
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}
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}
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}
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/**
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* Access the underlying data immutably. May run concurrently with other
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* reading tasks.
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*
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* # Failure
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*
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* Failing will unlock the ARC while unwinding. However, unlike all other
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* access modes, this will not poison the ARC.
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*/
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fn read<U>(&self, blk: &fn(x: &T) -> U) -> U {
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let state = unsafe { get_shared_immutable_state(&self.x) };
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do (&state.lock).read {
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check_poison(false, state.failed);
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blk(&state.data)
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}
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}
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/**
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* As write(), but with the ability to atomically 'downgrade' the lock.
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* See sync::rwlock.write_downgrade(). The RWWriteMode token must be used
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* to obtain the &mut T, and can be transformed into a RWReadMode token by
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* calling downgrade(), after which a &T can be obtained instead.
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* ~~~
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* do arc.write_downgrade |write_mode| {
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* do (&write_mode).write_cond |state, condvar| {
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* ... exclusive access with mutable state ...
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* }
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* let read_mode = arc.downgrade(write_mode);
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* do (&read_mode).read |state| {
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* ... shared access with immutable state ...
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* }
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* }
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* ~~~
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*/
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fn write_downgrade<U>(&self, blk: &fn(v: RWWriteMode<T>) -> U) -> U {
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unsafe {
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let state = get_shared_mutable_state(&self.x);
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do (*borrow_rwlock(state)).write_downgrade |write_mode| {
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check_poison(false, (*state).failed);
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blk(RWWriteMode {
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data: &mut (*state).data,
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token: write_mode,
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poison: PoisonOnFail(&mut (*state).failed)
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})
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}
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}
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}
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/// To be called inside of the write_downgrade block.
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fn downgrade<'a>(&self, token: RWWriteMode<'a, T>) -> RWReadMode<'a, T> {
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// The rwlock should assert that the token belongs to us for us.
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let state = unsafe { get_shared_immutable_state(&self.x) };
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let RWWriteMode {
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data: data,
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token: t,
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poison: _poison
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} = token;
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// Let readers in
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let new_token = (&state.lock).downgrade(t);
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// Whatever region the input reference had, it will be safe to use
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// the same region for the output reference. (The only 'unsafe' part
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// of this cast is removing the mutability.)
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let new_data = unsafe { cast::transmute_immut(data) };
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// Downgrade ensured the token belonged to us. Just a sanity check.
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assert!(ptr::ref_eq(&state.data, new_data));
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// Produce new token
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RWReadMode {
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data: new_data,
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token: new_token,
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}
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}
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}
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// Borrowck rightly complains about immutably aliasing the rwlock in order to
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// lock it. This wraps the unsafety, with the justification that the 'lock'
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// field is never overwritten; only 'failed' and 'data'.
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#[doc(hidden)]
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fn borrow_rwlock<T:Const + Owned>(state: *const RWARCInner<T>) -> *RWlock {
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unsafe { cast::transmute(&const (*state).lock) }
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}
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/// The "write permission" token used for RWARC.write_downgrade().
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pub struct RWWriteMode<'self, T> {
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data: &'self mut T,
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token: sync::RWlockWriteMode<'self>,
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poison: PoisonOnFail,
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}
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/// The "read permission" token used for RWARC.write_downgrade().
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pub struct RWReadMode<'self, T> {
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data: &'self T,
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token: sync::RWlockReadMode<'self>,
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}
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pub impl<'self, T:Const + Owned> RWWriteMode<'self, T> {
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/// Access the pre-downgrade RWARC in write mode.
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fn write<U>(&mut self, blk: &fn(x: &mut T) -> U) -> U {
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match *self {
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RWWriteMode {
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data: &ref mut data,
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token: ref token,
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poison: _
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} => {
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do token.write {
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blk(data)
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}
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}
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}
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}
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/// Access the pre-downgrade RWARC in write mode with a condvar.
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fn write_cond<'x, 'c, U>(&mut self,
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blk: &fn(x: &'x mut T, c: &'c Condvar) -> U)
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-> U {
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match *self {
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RWWriteMode {
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data: &ref mut data,
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token: ref token,
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poison: ref poison
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} => {
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do token.write_cond |cond| {
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unsafe {
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let cvar = Condvar {
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is_mutex: false,
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failed: &mut *poison.failed,
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cond: cond
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};
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blk(data, &cvar)
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}
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}
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}
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}
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}
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}
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pub impl<'self, T:Const + Owned> RWReadMode<'self, T> {
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/// Access the post-downgrade rwlock in read mode.
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fn read<U>(&self, blk: &fn(x: &T) -> U) -> U {
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match *self {
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RWReadMode {
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data: data,
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token: ref token
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} => {
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do token.read { blk(data) }
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}
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}
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}
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}
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/****************************************************************************
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* Tests
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****************************************************************************/
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#[cfg(test)]
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mod tests {
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use arc::*;
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use arc;
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use core::cell::Cell;
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use core::task;
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use core::vec;
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#[test]
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fn manually_share_arc() {
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let v = ~[1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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let arc_v = arc::ARC(v);
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let (p, c) = comm::stream();
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do task::spawn() || {
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let p = comm::PortSet::new();
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c.send(p.chan());
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let arc_v = p.recv();
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let v = *arc::get::<~[int]>(&arc_v);
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assert!(v[3] == 4);
|
|
};
|
|
|
|
let c = p.recv();
|
|
c.send(arc::clone(&arc_v));
|
|
|
|
assert!((*arc::get(&arc_v))[2] == 3);
|
|
|
|
info!(arc_v);
|
|
}
|
|
|
|
#[test]
|
|
fn test_mutex_arc_condvar() {
|
|
let arc = ~MutexARC(false);
|
|
let arc2 = ~arc.clone();
|
|
let (p,c) = comm::oneshot();
|
|
let (c,p) = (Cell(c), Cell(p));
|
|
do task::spawn || {
|
|
// wait until parent gets in
|
|
comm::recv_one(p.take());
|
|
do arc2.access_cond |state, cond| {
|
|
*state = true;
|
|
cond.signal();
|
|
}
|
|
}
|
|
do arc.access_cond |state, cond| {
|
|
comm::send_one(c.take(), ());
|
|
assert!(!*state);
|
|
while !*state {
|
|
cond.wait();
|
|
}
|
|
}
|
|
}
|
|
#[test] #[should_fail] #[ignore(cfg(windows))]
|
|
fn test_arc_condvar_poison() {
|
|
let arc = ~MutexARC(1);
|
|
let arc2 = ~arc.clone();
|
|
let (p, c) = comm::stream();
|
|
|
|
do task::spawn_unlinked || {
|
|
let _ = p.recv();
|
|
do arc2.access_cond |one, cond| {
|
|
cond.signal();
|
|
// Parent should fail when it wakes up.
|
|
assert!(*one == 0);
|
|
}
|
|
}
|
|
|
|
do arc.access_cond |one, cond| {
|
|
c.send(());
|
|
while *one == 1 {
|
|
cond.wait();
|
|
}
|
|
}
|
|
}
|
|
#[test] #[should_fail] #[ignore(cfg(windows))]
|
|
fn test_mutex_arc_poison() {
|
|
let arc = ~MutexARC(1);
|
|
let arc2 = ~arc.clone();
|
|
do task::try || {
|
|
do arc2.access |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
};
|
|
do arc.access |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test] #[should_fail] #[ignore(cfg(windows))]
|
|
fn test_rw_arc_poison_wr() {
|
|
let arc = ~RWARC(1);
|
|
let arc2 = (*arc).clone();
|
|
do task::try || {
|
|
do arc2.write |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
};
|
|
do arc.read |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test] #[should_fail] #[ignore(cfg(windows))]
|
|
fn test_rw_arc_poison_ww() {
|
|
let arc = ~RWARC(1);
|
|
let arc2 = (*arc).clone();
|
|
do task::try || {
|
|
do arc2.write |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
};
|
|
do arc.write |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test] #[should_fail] #[ignore(cfg(windows))]
|
|
fn test_rw_arc_poison_dw() {
|
|
let arc = ~RWARC(1);
|
|
let arc2 = (*arc).clone();
|
|
do task::try || {
|
|
do arc2.write_downgrade |mut write_mode| {
|
|
do write_mode.write |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
}
|
|
};
|
|
do arc.write |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test] #[ignore(cfg(windows))]
|
|
fn test_rw_arc_no_poison_rr() {
|
|
let arc = ~RWARC(1);
|
|
let arc2 = (*arc).clone();
|
|
do task::try || {
|
|
do arc2.read |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
};
|
|
do arc.read |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test] #[ignore(cfg(windows))]
|
|
fn test_rw_arc_no_poison_rw() {
|
|
let arc = ~RWARC(1);
|
|
let arc2 = (*arc).clone();
|
|
do task::try || {
|
|
do arc2.read |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
};
|
|
do arc.write |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test] #[ignore(cfg(windows))]
|
|
fn test_rw_arc_no_poison_dr() {
|
|
let arc = ~RWARC(1);
|
|
let arc2 = (*arc).clone();
|
|
do task::try || {
|
|
do arc2.write_downgrade |write_mode| {
|
|
let read_mode = arc2.downgrade(write_mode);
|
|
do (&read_mode).read |one| {
|
|
assert!(*one == 2);
|
|
}
|
|
}
|
|
};
|
|
do arc.write |one| {
|
|
assert!(*one == 1);
|
|
}
|
|
}
|
|
#[test]
|
|
fn test_rw_arc() {
|
|
let arc = ~RWARC(0);
|
|
let arc2 = (*arc).clone();
|
|
let (p,c) = comm::stream();
|
|
|
|
do task::spawn || {
|
|
do arc2.write |num| {
|
|
for 10.times {
|
|
let tmp = *num;
|
|
*num = -1;
|
|
task::yield();
|
|
*num = tmp + 1;
|
|
}
|
|
c.send(());
|
|
}
|
|
}
|
|
|
|
// Readers try to catch the writer in the act
|
|
let mut children = ~[];
|
|
for 5.times {
|
|
let arc3 = (*arc).clone();
|
|
do task::task().future_result(|+r| children.push(r)).spawn
|
|
|| {
|
|
do arc3.read |num| {
|
|
assert!(*num >= 0);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Wait for children to pass their asserts
|
|
for vec::each(children) |r| { r.recv(); }
|
|
|
|
// Wait for writer to finish
|
|
p.recv();
|
|
do arc.read |num| { assert!(*num == 10); }
|
|
}
|
|
#[test]
|
|
fn test_rw_downgrade() {
|
|
// (1) A downgrader gets in write mode and does cond.wait.
|
|
// (2) A writer gets in write mode, sets state to 42, and does signal.
|
|
// (3) Downgrader wakes, sets state to 31337.
|
|
// (4) tells writer and all other readers to contend as it downgrades.
|
|
// (5) Writer attempts to set state back to 42, while downgraded task
|
|
// and all reader tasks assert that it's 31337.
|
|
let arc = ~RWARC(0);
|
|
|
|
// Reader tasks
|
|
let mut reader_convos = ~[];
|
|
for 10.times {
|
|
let ((rp1,rc1),(rp2,rc2)) = (comm::stream(),comm::stream());
|
|
reader_convos.push((rc1, rp2));
|
|
let arcn = (*arc).clone();
|
|
do task::spawn || {
|
|
rp1.recv(); // wait for downgrader to give go-ahead
|
|
do arcn.read |state| {
|
|
assert!(*state == 31337);
|
|
rc2.send(());
|
|
}
|
|
}
|
|
}
|
|
|
|
// Writer task
|
|
let arc2 = (*arc).clone();
|
|
let ((wp1,wc1),(wp2,wc2)) = (comm::stream(),comm::stream());
|
|
do task::spawn || {
|
|
wp1.recv();
|
|
do arc2.write_cond |state, cond| {
|
|
assert!(*state == 0);
|
|
*state = 42;
|
|
cond.signal();
|
|
}
|
|
wp1.recv();
|
|
do arc2.write |state| {
|
|
// This shouldn't happen until after the downgrade read
|
|
// section, and all other readers, finish.
|
|
assert!(*state == 31337);
|
|
*state = 42;
|
|
}
|
|
wc2.send(());
|
|
}
|
|
|
|
// Downgrader (us)
|
|
do arc.write_downgrade |mut write_mode| {
|
|
do write_mode.write_cond |state, cond| {
|
|
wc1.send(()); // send to another writer who will wake us up
|
|
while *state == 0 {
|
|
cond.wait();
|
|
}
|
|
assert!(*state == 42);
|
|
*state = 31337;
|
|
// send to other readers
|
|
for vec::each(reader_convos) |x| {
|
|
match *x {
|
|
(ref rc, _) => rc.send(()),
|
|
}
|
|
}
|
|
}
|
|
let read_mode = arc.downgrade(write_mode);
|
|
do (&read_mode).read |state| {
|
|
// complete handshake with other readers
|
|
for vec::each(reader_convos) |x| {
|
|
match *x {
|
|
(_, ref rp) => rp.recv(),
|
|
}
|
|
}
|
|
wc1.send(()); // tell writer to try again
|
|
assert!(*state == 31337);
|
|
}
|
|
}
|
|
|
|
wp2.recv(); // complete handshake with writer
|
|
}
|
|
}
|