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rust/src/libextra/sync.rs
Daniel Micay 1008945528 remove obsolete foreach keyword 
this has been replaced by `for`
2013-08-03 22:48:02 -04:00

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// Copyright 2012-2013 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.
/**
* The concurrency primitives you know and love.
*
* Maybe once we have a "core exports x only to std" mechanism, these can be
* in std.
*/
use std::borrow;
use std::comm;
use std::comm::SendDeferred;
use std::task;
use std::unstable::sync::{Exclusive, UnsafeAtomicRcBox};
use std::unstable::atomics;
use std::unstable::finally::Finally;
use std::util;
use std::util::NonCopyable;
/****************************************************************************
* Internals
****************************************************************************/
// Each waiting task receives on one of these.
#[doc(hidden)]
type WaitEnd = comm::PortOne<()>;
#[doc(hidden)]
type SignalEnd = comm::ChanOne<()>;
// A doubly-ended queue of waiting tasks.
#[doc(hidden)]
struct WaitQueue { head: comm::Port<SignalEnd>,
tail: comm::Chan<SignalEnd> }
impl WaitQueue {
fn new() -> WaitQueue {
let (block_head, block_tail) = comm::stream();
WaitQueue { head: block_head, tail: block_tail }
}
// Signals one live task from the queue.
fn signal(&self) -> bool {
// The peek is mandatory to make sure recv doesn't block.
if self.head.peek() {
// Pop and send a wakeup signal. If the waiter was killed, its port
// will have closed. Keep trying until we get a live task.
if self.head.recv().try_send_deferred(()) {
true
} else {
self.signal()
}
} else {
false
}
}
fn broadcast(&self) -> uint {
let mut count = 0;
while self.head.peek() {
if self.head.recv().try_send_deferred(()) {
count += 1;
}
}
count
}
}
// The building-block used to make semaphores, mutexes, and rwlocks.
#[doc(hidden)]
struct SemInner<Q> {
count: int,
waiters: WaitQueue,
// Can be either unit or another waitqueue. Some sems shouldn't come with
// a condition variable attached, others should.
blocked: Q
}
#[doc(hidden)]
struct Sem<Q>(Exclusive<SemInner<Q>>);
#[doc(hidden)]
impl<Q:Send> Sem<Q> {
fn new(count: int, q: Q) -> Sem<Q> {
Sem(Exclusive::new(SemInner {
count: count, waiters: WaitQueue::new(), blocked: q }))
}
pub fn acquire(&self) {
unsafe {
let mut waiter_nobe = None;
do (**self).with |state| {
state.count -= 1;
if state.count < 0 {
// Create waiter nobe.
let (WaitEnd, SignalEnd) = comm::oneshot();
// Tell outer scope we need to block.
waiter_nobe = Some(WaitEnd);
// Enqueue ourself.
state.waiters.tail.send_deferred(SignalEnd);
}
}
// Uncomment if you wish to test for sem races. Not valgrind-friendly.
/* do 1000.times { task::yield(); } */
// Need to wait outside the exclusive.
if waiter_nobe.is_some() {
let _ = comm::recv_one(waiter_nobe.unwrap());
}
}
}
pub fn release(&self) {
unsafe {
do (**self).with |state| {
state.count += 1;
if state.count <= 0 {
state.waiters.signal();
}
}
}
}
pub fn access<U>(&self, blk: &fn() -> U) -> U {
do task::unkillable {
do (|| {
self.acquire();
unsafe {
do task::rekillable { blk() }
}
}).finally {
self.release();
}
}
}
}
#[doc(hidden)]
impl Sem<~[WaitQueue]> {
fn new_and_signal(count: int, num_condvars: uint)
-> Sem<~[WaitQueue]> {
let mut queues = ~[];
do num_condvars.times {
queues.push(WaitQueue::new());
}
Sem::new(count, queues)
}
}
// FIXME(#3598): Want to use an Option down below, but we need a custom enum
// that's not polymorphic to get around the fact that lifetimes are invariant
// inside of type parameters.
enum ReacquireOrderLock<'self> {
Nothing, // c.c
Just(&'self Semaphore),
}
/// A mechanism for atomic-unlock-and-deschedule blocking and signalling.
pub struct Condvar<'self> {
// The 'Sem' object associated with this condvar. This is the one that's
// atomically-unlocked-and-descheduled upon and reacquired during wakeup.
priv sem: &'self Sem<~[WaitQueue]>,
// This is (can be) an extra semaphore which is held around the reacquire
// operation on the first one. This is only used in cvars associated with
// rwlocks, and is needed to ensure that, when a downgrader is trying to
// hand off the access lock (which would be the first field, here), a 2nd
// writer waking up from a cvar wait can't race with a reader to steal it,
// See the comment in write_cond for more detail.
priv order: ReacquireOrderLock<'self>,
// Make sure condvars are non-copyable.
priv token: util::NonCopyable,
}
impl<'self> Condvar<'self> {
/**
* Atomically drop the associated lock, and block until a signal is sent.
*
* # Failure
* A task which is killed (i.e., by linked failure with another task)
* while waiting on a condition variable will wake up, fail, and unlock
* the associated lock as it unwinds.
*/
pub fn wait(&self) { self.wait_on(0) }
/**
* As wait(), but can specify which of multiple condition variables to
* wait on. Only a signal_on() or broadcast_on() with the same condvar_id
* will wake this thread.
*
* The associated lock must have been initialised with an appropriate
* number of condvars. The condvar_id must be between 0 and num_condvars-1
* or else this call will fail.
*
* wait() is equivalent to wait_on(0).
*/
pub fn wait_on(&self, condvar_id: uint) {
// Create waiter nobe.
let (WaitEnd, SignalEnd) = comm::oneshot();
let mut WaitEnd = Some(WaitEnd);
let mut SignalEnd = Some(SignalEnd);
let mut out_of_bounds = None;
do task::unkillable {
// Release lock, 'atomically' enqueuing ourselves in so doing.
unsafe {
do (**self.sem).with |state| {
if condvar_id < state.blocked.len() {
// Drop the lock.
state.count += 1;
if state.count <= 0 {
state.waiters.signal();
}
// Enqueue ourself to be woken up by a signaller.
let SignalEnd = SignalEnd.take_unwrap();
state.blocked[condvar_id].tail.send_deferred(SignalEnd);
} else {
out_of_bounds = Some(state.blocked.len());
}
}
}
// If yield checks start getting inserted anywhere, we can be
// killed before or after enqueueing. Deciding whether to
// unkillably reacquire the lock needs to happen atomically
// wrt enqueuing.
do check_cvar_bounds(out_of_bounds, condvar_id, "cond.wait_on()") {
// Unconditionally "block". (Might not actually block if a
// signaller already sent -- I mean 'unconditionally' in contrast
// with acquire().)
do (|| {
unsafe {
do task::rekillable {
let _ = comm::recv_one(WaitEnd.take_unwrap());
}
}
}).finally {
// Reacquire the condvar. Note this is back in the unkillable
// section; it needs to succeed, instead of itself dying.
match self.order {
Just(lock) => do lock.access {
self.sem.acquire();
},
Nothing => {
self.sem.acquire();
},
}
}
}
}
}
/// Wake up a blocked task. Returns false if there was no blocked task.
pub fn signal(&self) -> bool { self.signal_on(0) }
/// As signal, but with a specified condvar_id. See wait_on.
pub fn signal_on(&self, condvar_id: uint) -> bool {
unsafe {
let mut out_of_bounds = None;
let mut result = false;
do (**self.sem).with |state| {
if condvar_id < state.blocked.len() {
result = state.blocked[condvar_id].signal();
} else {
out_of_bounds = Some(state.blocked.len());
}
}
do check_cvar_bounds(out_of_bounds, condvar_id, "cond.signal_on()") {
result
}
}
}
/// Wake up all blocked tasks. Returns the number of tasks woken.
pub fn broadcast(&self) -> uint { self.broadcast_on(0) }
/// As broadcast, but with a specified condvar_id. See wait_on.
pub fn broadcast_on(&self, condvar_id: uint) -> uint {
let mut out_of_bounds = None;
let mut queue = None;
unsafe {
do (**self.sem).with |state| {
if condvar_id < state.blocked.len() {
// To avoid :broadcast_heavy, we make a new waitqueue,
// swap it out with the old one, and broadcast on the
// old one outside of the little-lock.
queue = Some(util::replace(&mut state.blocked[condvar_id],
WaitQueue::new()));
} else {
out_of_bounds = Some(state.blocked.len());
}
}
do check_cvar_bounds(out_of_bounds, condvar_id, "cond.signal_on()") {
let queue = queue.take_unwrap();
queue.broadcast()
}
}
}
}
// Checks whether a condvar ID was out of bounds, and fails if so, or does
// something else next on success.
#[inline]
#[doc(hidden)]
fn check_cvar_bounds<U>(out_of_bounds: Option<uint>, id: uint, act: &str,
blk: &fn() -> U) -> U {
match out_of_bounds {
Some(0) =>
fail!("%s with illegal ID %u - this lock has no condvars!", act, id),
Some(length) =>
fail!("%s with illegal ID %u - ID must be less than %u", act, id, length),
None => blk()
}
}
#[doc(hidden)]
impl Sem<~[WaitQueue]> {
// The only other places that condvars get built are rwlock.write_cond()
// and rwlock_write_mode.
pub fn access_cond<U>(&self, blk: &fn(c: &Condvar) -> U) -> U {
do self.access {
blk(&Condvar { sem: self, order: Nothing, token: NonCopyable::new() })
}
}
}
/****************************************************************************
* Semaphores
****************************************************************************/
/// A counting, blocking, bounded-waiting semaphore.
struct Semaphore { priv sem: Sem<()> }
impl Clone for Semaphore {
/// Create a new handle to the semaphore.
fn clone(&self) -> Semaphore {
Semaphore { sem: Sem((*self.sem).clone()) }
}
}
impl Semaphore {
/// Create a new semaphore with the specified count.
pub fn new(count: int) -> Semaphore {
Semaphore { sem: Sem::new(count, ()) }
}
/**
* Acquire a resource represented by the semaphore. Blocks if necessary
* until resource(s) become available.
*/
pub fn acquire(&self) { (&self.sem).acquire() }
/**
* Release a held resource represented by the semaphore. Wakes a blocked
* contending task, if any exist. Won't block the caller.
*/
pub fn release(&self) { (&self.sem).release() }
/// Run a function with ownership of one of the semaphore's resources.
pub fn access<U>(&self, blk: &fn() -> U) -> U { (&self.sem).access(blk) }
}
/****************************************************************************
* Mutexes
****************************************************************************/
/**
* A blocking, bounded-waiting, mutual exclusion lock with an associated
* FIFO condition variable.
*
* # Failure
* A task which fails while holding a mutex will unlock the mutex as it
* unwinds.
*/
pub struct Mutex { priv sem: Sem<~[WaitQueue]> }
impl Clone for Mutex {
/// Create a new handle to the mutex.
fn clone(&self) -> Mutex { Mutex { sem: Sem((*self.sem).clone()) } }
}
impl Mutex {
/// Create a new mutex, with one associated condvar.
pub fn new() -> Mutex { Mutex::new_with_condvars(1) }
/**
* Create a new mutex, with a specified number of associated condvars. This
* will allow calling wait_on/signal_on/broadcast_on with condvar IDs between
* 0 and num_condvars-1. (If num_condvars is 0, lock_cond will be allowed but
* any operations on the condvar will fail.)
*/
pub fn new_with_condvars(num_condvars: uint) -> Mutex {
Mutex { sem: Sem::new_and_signal(1, num_condvars) }
}
/// Run a function with ownership of the mutex.
pub fn lock<U>(&self, blk: &fn() -> U) -> U {
(&self.sem).access(blk)
}
/// Run a function with ownership of the mutex and a handle to a condvar.
pub fn lock_cond<U>(&self, blk: &fn(c: &Condvar) -> U) -> U {
(&self.sem).access_cond(blk)
}
}
/****************************************************************************
* Reader-writer locks
****************************************************************************/
// NB: Wikipedia - Readers-writers_problem#The_third_readers-writers_problem
#[doc(hidden)]
struct RWLockInner {
// You might ask, "Why don't you need to use an atomic for the mode flag?"
// This flag affects the behaviour of readers (for plain readers, they
// assert on it; for downgraders, they use it to decide which mode to
// unlock for). Consider that the flag is only unset when the very last
// reader exits; therefore, it can never be unset during a reader/reader
// (or reader/downgrader) race.
// By the way, if we didn't care about the assert in the read unlock path,
// we could instead store the mode flag in write_downgrade's stack frame,
// and have the downgrade tokens store a borrowed pointer to it.
read_mode: bool,
// The only way the count flag is ever accessed is with xadd. Since it is
// a read-modify-write operation, multiple xadds on different cores will
// always be consistent with respect to each other, so a monotonic/relaxed
// consistency ordering suffices (i.e., no extra barriers are needed).
// FIXME(#6598): The atomics module has no relaxed ordering flag, so I use
// acquire/release orderings superfluously. Change these someday.
read_count: atomics::AtomicUint,
}
/**
* A blocking, no-starvation, reader-writer lock with an associated condvar.
*
* # Failure
* A task which fails while holding an rwlock will unlock the rwlock as it
* unwinds.
*/
pub struct RWLock {
priv order_lock: Semaphore,
priv access_lock: Sem<~[WaitQueue]>,
priv state: UnsafeAtomicRcBox<RWLockInner>,
}
impl RWLock {
/// Create a new rwlock, with one associated condvar.
pub fn new() -> RWLock { RWLock::new_with_condvars(1) }
/**
* Create a new rwlock, with a specified number of associated condvars.
* Similar to mutex_with_condvars.
*/
pub fn new_with_condvars(num_condvars: uint) -> RWLock {
let state = UnsafeAtomicRcBox::new(RWLockInner {
read_mode: false,
read_count: atomics::AtomicUint::new(0),
});
RWLock { order_lock: Semaphore::new(1),
access_lock: Sem::new_and_signal(1, num_condvars),
state: state, }
}
/// Create a new handle to the rwlock.
pub fn clone(&self) -> RWLock {
RWLock { order_lock: (&(self.order_lock)).clone(),
access_lock: Sem((*self.access_lock).clone()),
state: self.state.clone() }
}
/**
* Run a function with the rwlock in read mode. Calls to 'read' from other
* tasks may run concurrently with this one.
*/
pub fn read<U>(&self, blk: &fn() -> U) -> U {
unsafe {
do task::unkillable {
do (&self.order_lock).access {
let state = &mut *self.state.get();
let old_count = state.read_count.fetch_add(1, atomics::Acquire);
if old_count == 0 {
(&self.access_lock).acquire();
state.read_mode = true;
}
}
do (|| {
do task::rekillable { blk() }
}).finally {
let state = &mut *self.state.get();
assert!(state.read_mode);
let old_count = state.read_count.fetch_sub(1, atomics::Release);
assert!(old_count > 0);
if old_count == 1 {
state.read_mode = false;
// Note: this release used to be outside of a locked access
// to exclusive-protected state. If this code is ever
// converted back to such (instead of using atomic ops),
// this access MUST NOT go inside the exclusive access.
(&self.access_lock).release();
}
}
}
}
}
/**
* Run a function with the rwlock in write mode. No calls to 'read' or
* 'write' from other tasks will run concurrently with this one.
*/
pub fn write<U>(&self, blk: &fn() -> U) -> U {
unsafe {
do task::unkillable {
(&self.order_lock).acquire();
do (&self.access_lock).access {
(&self.order_lock).release();
do task::rekillable {
blk()
}
}
}
}
}
/**
* As write(), but also with a handle to a condvar. Waiting on this
* condvar will allow readers and writers alike to take the rwlock before
* the waiting task is signalled. (Note: a writer that waited and then
* was signalled might reacquire the lock before other waiting writers.)
*/
pub fn write_cond<U>(&self, blk: &fn(c: &Condvar) -> U) -> U {
// It's important to thread our order lock into the condvar, so that
// when a cond.wait() wakes up, it uses it while reacquiring the
// access lock. If we permitted a waking-up writer to "cut in line",
// there could arise a subtle race when a downgrader attempts to hand
// off the reader cloud lock to a waiting reader. This race is tested
// in arc.rs (test_rw_write_cond_downgrade_read_race) and looks like:
// T1 (writer) T2 (downgrader) T3 (reader)
// [in cond.wait()]
// [locks for writing]
// [holds access_lock]
// [is signalled, perhaps by
// downgrader or a 4th thread]
// tries to lock access(!)
// lock order_lock
// xadd read_count[0->1]
// tries to lock access
// [downgrade]
// xadd read_count[1->2]
// unlock access
// Since T1 contended on the access lock before T3 did, it will steal
// the lock handoff. Adding order_lock in the condvar reacquire path
// solves this because T1 will hold order_lock while waiting on access,
// which will cause T3 to have to wait until T1 finishes its write,
// which can't happen until T2 finishes the downgrade-read entirely.
// The astute reader will also note that making waking writers use the
// order_lock is better for not starving readers.
unsafe {
do task::unkillable {
(&self.order_lock).acquire();
do (&self.access_lock).access_cond |cond| {
(&self.order_lock).release();
do task::rekillable {
let opt_lock = Just(&self.order_lock);
blk(&Condvar { sem: cond.sem, order: opt_lock,
token: NonCopyable::new() })
}
}
}
}
}
/**
* As write(), but with the ability to atomically 'downgrade' the lock;
* i.e., to become a reader without letting other writers get the lock in
* the meantime (such as unlocking and then re-locking as a reader would
* do). The block takes a "write mode token" argument, which can be
* transformed into a "read mode token" by calling downgrade(). Example:
*
* # Example
*
* ~~~ {.rust}
* do lock.write_downgrade |mut write_token| {
* do write_token.write_cond |condvar| {
* ... exclusive access ...
* }
* let read_token = lock.downgrade(write_token);
* do read_token.read {
* ... shared access ...
* }
* }
* ~~~
*/
pub fn write_downgrade<U>(&self, blk: &fn(v: RWLockWriteMode) -> U) -> U {
// Implementation slightly different from the slicker 'write's above.
// The exit path is conditional on whether the caller downgrades.
do task::unkillable {
(&self.order_lock).acquire();
(&self.access_lock).acquire();
(&self.order_lock).release();
do (|| {
unsafe {
do task::rekillable {
blk(RWLockWriteMode { lock: self, token: NonCopyable::new() })
}
}
}).finally {
let writer_or_last_reader;
// Check if we're releasing from read mode or from write mode.
let state = unsafe { &mut *self.state.get() };
if state.read_mode {
// Releasing from read mode.
let old_count = state.read_count.fetch_sub(1, atomics::Release);
assert!(old_count > 0);
// Check if other readers remain.
if old_count == 1 {
// Case 1: Writer downgraded & was the last reader
writer_or_last_reader = true;
state.read_mode = false;
} else {
// Case 2: Writer downgraded & was not the last reader
writer_or_last_reader = false;
}
} else {
// Case 3: Writer did not downgrade
writer_or_last_reader = true;
}
if writer_or_last_reader {
// Nobody left inside; release the "reader cloud" lock.
(&self.access_lock).release();
}
}
}
}
/// To be called inside of the write_downgrade block.
pub fn downgrade<'a>(&self, token: RWLockWriteMode<'a>)
-> RWLockReadMode<'a> {
if !borrow::ref_eq(self, token.lock) {
fail!("Can't downgrade() with a different rwlock's write_mode!");
}
unsafe {
do task::unkillable {
let state = &mut *self.state.get();
assert!(!state.read_mode);
state.read_mode = true;
// If a reader attempts to enter at this point, both the
// downgrader and reader will set the mode flag. This is fine.
let old_count = state.read_count.fetch_add(1, atomics::Release);
// If another reader was already blocking, we need to hand-off
// the "reader cloud" access lock to them.
if old_count != 0 {
// Guaranteed not to let another writer in, because
// another reader was holding the order_lock. Hence they
// must be the one to get the access_lock (because all
// access_locks are acquired with order_lock held). See
// the comment in write_cond for more justification.
(&self.access_lock).release();
}
}
}
RWLockReadMode { lock: token.lock, token: NonCopyable::new() }
}
}
/// The "write permission" token used for rwlock.write_downgrade().
pub struct RWLockWriteMode<'self> { priv lock: &'self RWLock, priv token: NonCopyable }
/// The "read permission" token used for rwlock.write_downgrade().
pub struct RWLockReadMode<'self> { priv lock: &'self RWLock,
priv token: NonCopyable }
impl<'self> RWLockWriteMode<'self> {
/// Access the pre-downgrade rwlock in write mode.
pub fn write<U>(&self, blk: &fn() -> U) -> U { blk() }
/// Access the pre-downgrade rwlock in write mode with a condvar.
pub fn write_cond<U>(&self, blk: &fn(c: &Condvar) -> U) -> U {
// Need to make the condvar use the order lock when reacquiring the
// access lock. See comment in RWLock::write_cond for why.
blk(&Condvar { sem: &self.lock.access_lock,
order: Just(&self.lock.order_lock),
token: NonCopyable::new() })
}
}
impl<'self> RWLockReadMode<'self> {
/// Access the post-downgrade rwlock in read mode.
pub fn read<U>(&self, blk: &fn() -> U) -> U { blk() }
}
/****************************************************************************
* Tests
****************************************************************************/
#[cfg(test)]
mod tests {
use sync::*;
use std::cast;
use std::cell::Cell;
use std::comm;
use std::result;
use std::task;
/************************************************************************
* Semaphore tests
************************************************************************/
#[test]
fn test_sem_acquire_release() {
let s = ~Semaphore::new(1);
s.acquire();
s.release();
s.acquire();
}
#[test]
fn test_sem_basic() {
let s = ~Semaphore::new(1);
do s.access { }
}
#[test]
fn test_sem_as_mutex() {
let s = ~Semaphore::new(1);
let s2 = ~s.clone();
do task::spawn || {
do s2.access {
do 5.times { task::yield(); }
}
}
do s.access {
do 5.times { task::yield(); }
}
}
#[test]
fn test_sem_as_cvar() {
/* Child waits and parent signals */
let (p,c) = comm::stream();
let s = ~Semaphore::new(0);
let s2 = ~s.clone();
do task::spawn || {
s2.acquire();
c.send(());
}
do 5.times { task::yield(); }
s.release();
let _ = p.recv();
/* Parent waits and child signals */
let (p,c) = comm::stream();
let s = ~Semaphore::new(0);
let s2 = ~s.clone();
do task::spawn || {
do 5.times { task::yield(); }
s2.release();
let _ = p.recv();
}
s.acquire();
c.send(());
}
#[test]
fn test_sem_multi_resource() {
// Parent and child both get in the critical section at the same
// time, and shake hands.
let s = ~Semaphore::new(2);
let s2 = ~s.clone();
let (p1,c1) = comm::stream();
let (p2,c2) = comm::stream();
do task::spawn || {
do s2.access {
let _ = p2.recv();
c1.send(());
}
}
do s.access {
c2.send(());
let _ = p1.recv();
}
}
#[test]
fn test_sem_runtime_friendly_blocking() {
// Force the runtime to schedule two threads on the same sched_loop.
// When one blocks, it should schedule the other one.
do task::spawn_sched(task::SingleThreaded) {
let s = ~Semaphore::new(1);
let s2 = ~s.clone();
let (p,c) = comm::stream();
let child_data = Cell::new((s2, c));
do s.access {
let (s2, c) = child_data.take();
do task::spawn || {
c.send(());
do s2.access { }
c.send(());
}
let _ = p.recv(); // wait for child to come alive
do 5.times { task::yield(); } // let the child contend
}
let _ = p.recv(); // wait for child to be done
}
}
/************************************************************************
* Mutex tests
************************************************************************/
#[test]
fn test_mutex_lock() {
// Unsafely achieve shared state, and do the textbook
// "load tmp = move ptr; inc tmp; store ptr <- tmp" dance.
let (p,c) = comm::stream();
let m = ~Mutex::new();
let m2 = m.clone();
let mut sharedstate = ~0;
{
let ptr: *int = &*sharedstate;
do task::spawn || {
let sharedstate: &mut int =
unsafe { cast::transmute(ptr) };
access_shared(sharedstate, m2, 10);
c.send(());
}
}
{
access_shared(sharedstate, m, 10);
let _ = p.recv();
assert_eq!(*sharedstate, 20);
}
fn access_shared(sharedstate: &mut int, m: &Mutex, n: uint) {
do n.times {
do m.lock {
let oldval = *sharedstate;
task::yield();
*sharedstate = oldval + 1;
}
}
}
}
#[test]
fn test_mutex_cond_wait() {
let m = ~Mutex::new();
// Child wakes up parent
do m.lock_cond |cond| {
let m2 = ~m.clone();
do task::spawn || {
do m2.lock_cond |cond| {
let woken = cond.signal();
assert!(woken);
}
}
cond.wait();
}
// Parent wakes up child
let (port,chan) = comm::stream();
let m3 = ~m.clone();
do task::spawn || {
do m3.lock_cond |cond| {
chan.send(());
cond.wait();
chan.send(());
}
}
let _ = port.recv(); // Wait until child gets in the mutex
do m.lock_cond |cond| {
let woken = cond.signal();
assert!(woken);
}
let _ = port.recv(); // Wait until child wakes up
}
#[cfg(test)]
fn test_mutex_cond_broadcast_helper(num_waiters: uint) {
let m = ~Mutex::new();
let mut ports = ~[];
do num_waiters.times {
let mi = ~m.clone();
let (port, chan) = comm::stream();
ports.push(port);
do task::spawn || {
do mi.lock_cond |cond| {
chan.send(());
cond.wait();
chan.send(());
}
}
}
// wait until all children get in the mutex
for port in ports.iter() { let _ = port.recv(); }
do m.lock_cond |cond| {
let num_woken = cond.broadcast();
assert_eq!(num_woken, num_waiters);
}
// wait until all children wake up
for port in ports.iter() { let _ = port.recv(); }
}
#[test]
fn test_mutex_cond_broadcast() {
test_mutex_cond_broadcast_helper(12);
}
#[test]
fn test_mutex_cond_broadcast_none() {
test_mutex_cond_broadcast_helper(0);
}
#[test]
fn test_mutex_cond_no_waiter() {
let m = ~Mutex::new();
let m2 = ~m.clone();
do task::try || {
do m.lock_cond |_x| { }
};
do m2.lock_cond |cond| {
assert!(!cond.signal());
}
}
#[test] #[ignore(cfg(windows))]
fn test_mutex_killed_simple() {
// Mutex must get automatically unlocked if failed/killed within.
let m = ~Mutex::new();
let m2 = ~m.clone();
let result: result::Result<(),()> = do task::try || {
do m2.lock {
fail!();
}
};
assert!(result.is_err());
// child task must have finished by the time try returns
do m.lock { }
}
#[test] #[ignore(cfg(windows))]
fn test_mutex_killed_cond() {
// Getting killed during cond wait must not corrupt the mutex while
// unwinding (e.g. double unlock).
let m = ~Mutex::new();
let m2 = ~m.clone();
let result: result::Result<(),()> = do task::try || {
let (p,c) = comm::stream();
do task::spawn || { // linked
let _ = p.recv(); // wait for sibling to get in the mutex
task::yield();
fail!();
}
do m2.lock_cond |cond| {
c.send(()); // tell sibling go ahead
cond.wait(); // block forever
}
};
assert!(result.is_err());
// child task must have finished by the time try returns
do m.lock_cond |cond| {
let woken = cond.signal();
assert!(!woken);
}
}
#[test] #[ignore(cfg(windows))]
fn test_mutex_killed_broadcast() {
use std::unstable::finally::Finally;
let m = ~Mutex::new();
let m2 = ~m.clone();
let (p,c) = comm::stream();
let result: result::Result<(),()> = do task::try || {
let mut sibling_convos = ~[];
do 2.times {
let (p,c) = comm::stream();
let c = Cell::new(c);
sibling_convos.push(p);
let mi = ~m2.clone();
// spawn sibling task
do task::spawn { // linked
do mi.lock_cond |cond| {
let c = c.take();
c.send(()); // tell sibling to go ahead
do (|| {
cond.wait(); // block forever
}).finally {
error!("task unwinding and sending");
c.send(());
error!("task unwinding and done sending");
}
}
}
}
for p in sibling_convos.iter() {
let _ = p.recv(); // wait for sibling to get in the mutex
}
do m2.lock { }
c.send(sibling_convos); // let parent wait on all children
fail!();
};
assert!(result.is_err());
// child task must have finished by the time try returns
let r = p.recv();
for p in r.iter() { p.recv(); } // wait on all its siblings
do m.lock_cond |cond| {
let woken = cond.broadcast();
assert_eq!(woken, 0);
}
}
#[test]
fn test_mutex_cond_signal_on_0() {
// Tests that signal_on(0) is equivalent to signal().
let m = ~Mutex::new();
do m.lock_cond |cond| {
let m2 = ~m.clone();
do task::spawn || {
do m2.lock_cond |cond| {
cond.signal_on(0);
}
}
cond.wait();
}
}
#[test] #[ignore(cfg(windows))]
fn test_mutex_different_conds() {
let result = do task::try {
let m = ~Mutex::new_with_condvars(2);
let m2 = ~m.clone();
let (p,c) = comm::stream();
do task::spawn || {
do m2.lock_cond |cond| {
c.send(());
cond.wait_on(1);
}
}
let _ = p.recv();
do m.lock_cond |cond| {
if !cond.signal_on(0) {
fail!(); // success; punt sibling awake.
}
}
};
assert!(result.is_err());
}
#[test] #[ignore(cfg(windows))]
fn test_mutex_no_condvars() {
let result = do task::try {
let m = ~Mutex::new_with_condvars(0);
do m.lock_cond |cond| { cond.wait(); }
};
assert!(result.is_err());
let result = do task::try {
let m = ~Mutex::new_with_condvars(0);
do m.lock_cond |cond| { cond.signal(); }
};
assert!(result.is_err());
let result = do task::try {
let m = ~Mutex::new_with_condvars(0);
do m.lock_cond |cond| { cond.broadcast(); }
};
assert!(result.is_err());
}
/************************************************************************
* Reader/writer lock tests
************************************************************************/
#[cfg(test)]
pub enum RWLockMode { Read, Write, Downgrade, DowngradeRead }
#[cfg(test)]
fn lock_rwlock_in_mode(x: &RWLock, mode: RWLockMode, blk: &fn()) {
match mode {
Read => x.read(blk),
Write => x.write(blk),
Downgrade =>
do x.write_downgrade |mode| {
do mode.write { blk() };
},
DowngradeRead =>
do x.write_downgrade |mode| {
let mode = x.downgrade(mode);
do mode.read { blk() };
},
}
}
#[cfg(test)]
fn test_rwlock_exclusion(x: ~RWLock,
mode1: RWLockMode,
mode2: RWLockMode) {
// Test mutual exclusion between readers and writers. Just like the
// mutex mutual exclusion test, a ways above.
let (p,c) = comm::stream();
let x2 = (*x).clone();
let mut sharedstate = ~0;
{
let ptr: *int = &*sharedstate;
do task::spawn || {
let sharedstate: &mut int =
unsafe { cast::transmute(ptr) };
access_shared(sharedstate, &x2, mode1, 10);
c.send(());
}
}
{
access_shared(sharedstate, x, mode2, 10);
let _ = p.recv();
assert_eq!(*sharedstate, 20);
}
fn access_shared(sharedstate: &mut int, x: &RWLock, mode: RWLockMode,
n: uint) {
do n.times {
do lock_rwlock_in_mode(x, mode) {
let oldval = *sharedstate;
task::yield();
*sharedstate = oldval + 1;
}
}
}
}
#[test]
fn test_rwlock_readers_wont_modify_the_data() {
test_rwlock_exclusion(~RWLock::new(), Read, Write);
test_rwlock_exclusion(~RWLock::new(), Write, Read);
test_rwlock_exclusion(~RWLock::new(), Read, Downgrade);
test_rwlock_exclusion(~RWLock::new(), Downgrade, Read);
}
#[test]
fn test_rwlock_writers_and_writers() {
test_rwlock_exclusion(~RWLock::new(), Write, Write);
test_rwlock_exclusion(~RWLock::new(), Write, Downgrade);
test_rwlock_exclusion(~RWLock::new(), Downgrade, Write);
test_rwlock_exclusion(~RWLock::new(), Downgrade, Downgrade);
}
#[cfg(test)]
fn test_rwlock_handshake(x: ~RWLock,
mode1: RWLockMode,
mode2: RWLockMode,
make_mode2_go_first: bool) {
// Much like sem_multi_resource.
let x2 = (*x).clone();
let (p1,c1) = comm::stream();
let (p2,c2) = comm::stream();
do task::spawn || {
if !make_mode2_go_first {
let _ = p2.recv(); // parent sends to us once it locks, or ...
}
do lock_rwlock_in_mode(&x2, mode2) {
if make_mode2_go_first {
c1.send(()); // ... we send to it once we lock
}
let _ = p2.recv();
c1.send(());
}
}
if make_mode2_go_first {
let _ = p1.recv(); // child sends to us once it locks, or ...
}
do lock_rwlock_in_mode(x, mode1) {
if !make_mode2_go_first {
c2.send(()); // ... we send to it once we lock
}
c2.send(());
let _ = p1.recv();
}
}
#[test]
fn test_rwlock_readers_and_readers() {
test_rwlock_handshake(~RWLock::new(), Read, Read, false);
// The downgrader needs to get in before the reader gets in, otherwise
// they cannot end up reading at the same time.
test_rwlock_handshake(~RWLock::new(), DowngradeRead, Read, false);
test_rwlock_handshake(~RWLock::new(), Read, DowngradeRead, true);
// Two downgrade_reads can never both end up reading at the same time.
}
#[test]
fn test_rwlock_downgrade_unlock() {
// Tests that downgrade can unlock the lock in both modes
let x = ~RWLock::new();
do lock_rwlock_in_mode(x, Downgrade) { }
test_rwlock_handshake(x, Read, Read, false);
let y = ~RWLock::new();
do lock_rwlock_in_mode(y, DowngradeRead) { }
test_rwlock_exclusion(y, Write, Write);
}
#[test]
fn test_rwlock_read_recursive() {
let x = ~RWLock::new();
do x.read { do x.read { } }
}
#[test]
fn test_rwlock_cond_wait() {
// As test_mutex_cond_wait above.
let x = ~RWLock::new();
// Child wakes up parent
do x.write_cond |cond| {
let x2 = (*x).clone();
do task::spawn || {
do x2.write_cond |cond| {
let woken = cond.signal();
assert!(woken);
}
}
cond.wait();
}
// Parent wakes up child
let (port,chan) = comm::stream();
let x3 = (*x).clone();
do task::spawn || {
do x3.write_cond |cond| {
chan.send(());
cond.wait();
chan.send(());
}
}
let _ = port.recv(); // Wait until child gets in the rwlock
do x.read { } // Must be able to get in as a reader in the meantime
do x.write_cond |cond| { // Or as another writer
let woken = cond.signal();
assert!(woken);
}
let _ = port.recv(); // Wait until child wakes up
do x.read { } // Just for good measure
}
#[cfg(test)]
fn test_rwlock_cond_broadcast_helper(num_waiters: uint,
dg1: bool,
dg2: bool) {
// Much like the mutex broadcast test. Downgrade-enabled.
fn lock_cond(x: &RWLock, downgrade: bool, blk: &fn(c: &Condvar)) {
if downgrade {
do x.write_downgrade |mode| {
do mode.write_cond |c| { blk(c) }
}
} else {
do x.write_cond |c| { blk(c) }
}
}
let x = ~RWLock::new();
let mut ports = ~[];
do num_waiters.times {
let xi = (*x).clone();
let (port, chan) = comm::stream();
ports.push(port);
do task::spawn || {
do lock_cond(&xi, dg1) |cond| {
chan.send(());
cond.wait();
chan.send(());
}
}
}
// wait until all children get in the mutex
for port in ports.iter() { let _ = port.recv(); }
do lock_cond(x, dg2) |cond| {
let num_woken = cond.broadcast();
assert_eq!(num_woken, num_waiters);
}
// wait until all children wake up
for port in ports.iter() { let _ = port.recv(); }
}
#[test]
fn test_rwlock_cond_broadcast() {
test_rwlock_cond_broadcast_helper(0, true, true);
test_rwlock_cond_broadcast_helper(0, true, false);
test_rwlock_cond_broadcast_helper(0, false, true);
test_rwlock_cond_broadcast_helper(0, false, false);
test_rwlock_cond_broadcast_helper(12, true, true);
test_rwlock_cond_broadcast_helper(12, true, false);
test_rwlock_cond_broadcast_helper(12, false, true);
test_rwlock_cond_broadcast_helper(12, false, false);
}
#[cfg(test)] #[ignore(cfg(windows))]
fn rwlock_kill_helper(mode1: RWLockMode, mode2: RWLockMode) {
// Mutex must get automatically unlocked if failed/killed within.
let x = ~RWLock::new();
let x2 = (*x).clone();
let result: result::Result<(),()> = do task::try || {
do lock_rwlock_in_mode(&x2, mode1) {
fail!();
}
};
assert!(result.is_err());
// child task must have finished by the time try returns
do lock_rwlock_in_mode(x, mode2) { }
}
#[test] #[ignore(cfg(windows))]
fn test_rwlock_reader_killed_writer() {
rwlock_kill_helper(Read, Write);
}
#[test] #[ignore(cfg(windows))]
fn test_rwlock_writer_killed_reader() {
rwlock_kill_helper(Write,Read );
}
#[test] #[ignore(cfg(windows))]
fn test_rwlock_reader_killed_reader() {
rwlock_kill_helper(Read, Read );
}
#[test] #[ignore(cfg(windows))]
fn test_rwlock_writer_killed_writer() {
rwlock_kill_helper(Write,Write);
}
#[test] #[ignore(cfg(windows))]
fn test_rwlock_kill_downgrader() {
rwlock_kill_helper(Downgrade, Read);
rwlock_kill_helper(Read, Downgrade);
rwlock_kill_helper(Downgrade, Write);
rwlock_kill_helper(Write, Downgrade);
rwlock_kill_helper(DowngradeRead, Read);
rwlock_kill_helper(Read, DowngradeRead);
rwlock_kill_helper(DowngradeRead, Write);
rwlock_kill_helper(Write, DowngradeRead);
rwlock_kill_helper(DowngradeRead, Downgrade);
rwlock_kill_helper(DowngradeRead, Downgrade);
rwlock_kill_helper(Downgrade, DowngradeRead);
rwlock_kill_helper(Downgrade, DowngradeRead);
}
#[test] #[should_fail] #[ignore(cfg(windows))]
fn test_rwlock_downgrade_cant_swap() {
// Tests that you can't downgrade with a different rwlock's token.
let x = ~RWLock::new();
let y = ~RWLock::new();
do x.write_downgrade |xwrite| {
let mut xopt = Some(xwrite);
do y.write_downgrade |_ywrite| {
y.downgrade(xopt.take_unwrap());
error!("oops, y.downgrade(x) should have failed!");
}
}
}
}
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