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Auto merge of #33861 - Amanieu:lock_elision_fix, r=alexcrichton

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Make sure Mutex and RwLock can't be re-locked on the same thread

Fixes #33770

r? @alexcrichton
This commit is contained in:
bors 2016-06-03 04:09:31 -07:00
commit 9552bcdd92
7 changed files with 214 additions and 11 deletions
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2
src/liblibc

@ -1 +1 @@
Subproject commit b19b5465a1235be3323363cdc11838739b593029
Subproject commit 45d85899e99d33e291b2bf3259881b46cc5365d7

6
src/libstd/sync/mutex.rs
View File

@ -204,10 +204,14 @@ impl<T> Mutex<T> {
/// Creates a new mutex in an unlocked state ready for use.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(t: T) -> Mutex<T> {
Mutex {
let mut m = Mutex {
inner: box StaticMutex::new(),
data: UnsafeCell::new(t),
};
unsafe {
m.inner.lock.init();
}
m
}
}

6
src/libstd/sys/common/mutex.rs
View File

@ -27,6 +27,12 @@ impl Mutex {
/// first used with any of the functions below.
pub const fn new() -> Mutex { Mutex(imp::Mutex::new()) }
/// Prepare the mutex for use.
///
/// This should be called once the mutex is at a stable memory address.
#[inline]
pub unsafe fn init(&mut self) { self.0.init() }
/// Locks the mutex blocking the current thread until it is available.
///
/// Behavior is undefined if the mutex has been moved between this and any

33
src/libstd/sys/unix/mutex.rs
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@ -30,6 +30,39 @@ impl Mutex {
Mutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
}
#[inline]
pub unsafe fn init(&mut self) {
// Issue #33770
//
// A pthread mutex initialized with PTHREAD_MUTEX_INITIALIZER will have
// a type of PTHREAD_MUTEX_DEFAULT, which has undefined behavior if you
// try to re-lock it from the same thread when you already hold a lock.
//
// In practice, glibc takes advantage of this undefined behavior to
// implement hardware lock elision, which uses hardware transactional
// memory to avoid acquiring the lock. While a transaction is in
// progress, the lock appears to be unlocked. This isn't a problem for
// other threads since the transactional memory will abort if a conflict
// is detected, however no abort is generated if re-locking from the
// same thread.
//
// Since locking the same mutex twice will result in two aliasing &mut
// references, we instead create the mutex with type
// PTHREAD_MUTEX_NORMAL which is guaranteed to deadlock if we try to
// re-lock it from the same thread, thus avoiding undefined behavior.
//
// We can't do anything for StaticMutex, but that type is deprecated
// anyways.
let mut attr: libc::pthread_mutexattr_t = mem::uninitialized();
let r = libc::pthread_mutexattr_init(&mut attr);
debug_assert_eq!(r, 0);
let r = libc::pthread_mutexattr_settype(&mut attr, libc::PTHREAD_MUTEX_NORMAL);
debug_assert_eq!(r, 0);
let r = libc::pthread_mutex_init(self.inner.get(), &attr);
debug_assert_eq!(r, 0);
let r = libc::pthread_mutexattr_destroy(&mut attr);
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn lock(&self) {
let r = libc::pthread_mutex_lock(self.inner.get());
debug_assert_eq!(r, 0);

76
src/libstd/sys/unix/rwlock.rs
View File

@ -10,15 +10,24 @@
use libc;
use cell::UnsafeCell;
use sync::atomic::{AtomicUsize, Ordering};
pub struct RWLock { inner: UnsafeCell<libc::pthread_rwlock_t> }
pub struct RWLock {
inner: UnsafeCell<libc::pthread_rwlock_t>,
write_locked: UnsafeCell<bool>,
num_readers: AtomicUsize,
}
unsafe impl Send for RWLock {}
unsafe impl Sync for RWLock {}
impl RWLock {
pub const fn new() -> RWLock {
RWLock { inner: UnsafeCell::new(libc::PTHREAD_RWLOCK_INITIALIZER) }
RWLock {
inner: UnsafeCell::new(libc::PTHREAD_RWLOCK_INITIALIZER),
write_locked: UnsafeCell::new(false),
num_readers: AtomicUsize::new(0),
}
}
#[inline]
pub unsafe fn read(&self) {
@ -35,37 +44,86 @@ impl RWLock {
//
// We roughly maintain the deadlocking behavior by panicking to ensure
// that this lock acquisition does not succeed.
if r == libc::EDEADLK {
//
// We also check whether there this lock is already write locked. This
// is only possible if it was write locked by the current thread and
// the implementation allows recursive locking. The POSIX standard
// doesn't require recursivly locking a rwlock to deadlock, but we can't
// allow that because it could lead to aliasing issues.
if r == libc::EDEADLK || *self.write_locked.get() {
if r == 0 {
self.raw_unlock();
}
panic!("rwlock read lock would result in deadlock");
} else {
debug_assert_eq!(r, 0);
self.num_readers.fetch_add(1, Ordering::Relaxed);
}
}
#[inline]
pub unsafe fn try_read(&self) -> bool {
libc::pthread_rwlock_tryrdlock(self.inner.get()) == 0
let r = libc::pthread_rwlock_tryrdlock(self.inner.get());
if r == 0 {
if *self.write_locked.get() {
self.raw_unlock();
false
} else {
self.num_readers.fetch_add(1, Ordering::Relaxed);
true
}
} else {
false
}
}
#[inline]
pub unsafe fn write(&self) {
let r = libc::pthread_rwlock_wrlock(self.inner.get());
// see comments above for why we check for EDEADLK
if r == libc::EDEADLK {
// See comments above for why we check for EDEADLK and write_locked. We
// also need to check that num_readers is 0.
if r == libc::EDEADLK || *self.write_locked.get() ||
self.num_readers.load(Ordering::Relaxed) != 0 {
if r == 0 {
self.raw_unlock();
}
panic!("rwlock write lock would result in deadlock");
} else {
debug_assert_eq!(r, 0);
}
*self.write_locked.get() = true;
}
#[inline]
pub unsafe fn try_write(&self) -> bool {
libc::pthread_rwlock_trywrlock(self.inner.get()) == 0
let r = libc::pthread_rwlock_trywrlock(self.inner.get());
if r == 0 {
if *self.write_locked.get() || self.num_readers.load(Ordering::Relaxed) != 0 {
self.raw_unlock();
false
} else {
*self.write_locked.get() = true;
true
}
} else {
false
}
}
#[inline]
pub unsafe fn read_unlock(&self) {
unsafe fn raw_unlock(&self) {
let r = libc::pthread_rwlock_unlock(self.inner.get());
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn write_unlock(&self) { self.read_unlock() }
pub unsafe fn read_unlock(&self) {
debug_assert!(!*self.write_locked.get());
self.num_readers.fetch_sub(1, Ordering::Relaxed);
self.raw_unlock();
}
#[inline]
pub unsafe fn write_unlock(&self) {
debug_assert_eq!(self.num_readers.load(Ordering::Relaxed), 0);
debug_assert!(*self.write_locked.get());
*self.write_locked.get() = false;
self.raw_unlock();
}
#[inline]
pub unsafe fn destroy(&self) {
let r = libc::pthread_rwlock_destroy(self.inner.get());

2
src/libstd/sys/windows/mutex.rs
View File

@ -64,6 +64,8 @@ impl Mutex {
held: UnsafeCell::new(false),
}
}
#[inline]
pub unsafe fn init(&mut self) {}
pub unsafe fn lock(&self) {
match kind() {
Kind::SRWLock => c::AcquireSRWLockExclusive(raw(self)),

100
src/test/run-pass/issue-33770.rs Normal file
View File

@ -0,0 +1,100 @@
// Copyright 2016 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 std::process::{Command, Stdio};
use std::env;
use std::sync::{Mutex, RwLock};
use std::time::Duration;
use std::thread;
fn test_mutex() {
let m = Mutex::new(0);
let _g = m.lock().unwrap();
let _g2 = m.lock().unwrap();
}
fn test_try_mutex() {
let m = Mutex::new(0);
let _g = m.lock().unwrap();
let _g2 = m.try_lock().unwrap();
}
fn test_rwlock_ww() {
let m = RwLock::new(0);
let _g = m.write().unwrap();
let _g2 = m.write().unwrap();
}
fn test_try_rwlock_ww() {
let m = RwLock::new(0);
let _g = m.write().unwrap();
let _g2 = m.try_write().unwrap();
}
fn test_rwlock_rw() {
let m = RwLock::new(0);
let _g = m.read().unwrap();
let _g2 = m.write().unwrap();
}
fn test_try_rwlock_rw() {
let m = RwLock::new(0);
let _g = m.read().unwrap();
let _g2 = m.try_write().unwrap();
}
fn test_rwlock_wr() {
let m = RwLock::new(0);
let _g = m.write().unwrap();
let _g2 = m.read().unwrap();
}
fn test_try_rwlock_wr() {
let m = RwLock::new(0);
let _g = m.write().unwrap();
let _g2 = m.try_read().unwrap();
}
fn main() {
let args: Vec<String> = env::args().collect();
if args.len() > 1 {
match &*args[1] {
"mutex" => test_mutex(),
"try_mutex" => test_try_mutex(),
"rwlock_ww" => test_rwlock_ww(),
"try_rwlock_ww" => test_try_rwlock_ww(),
"rwlock_rw" => test_rwlock_rw(),
"try_rwlock_rw" => test_try_rwlock_rw(),
"rwlock_wr" => test_rwlock_wr(),
"try_rwlock_wr" => test_try_rwlock_wr(),
_ => unreachable!(),
}
// If we reach this point then the test failed
println!("TEST FAILED: {}", args[1]);
} else {
let mut v = vec![];
v.push(Command::new(&args[0]).arg("mutex").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("try_mutex").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("rwlock_ww").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("try_rwlock_ww").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("rwlock_rw").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("try_rwlock_rw").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("rwlock_wr").stderr(Stdio::null()).spawn().unwrap());
v.push(Command::new(&args[0]).arg("try_rwlock_wr").stderr(Stdio::null()).spawn().unwrap());
thread::sleep(Duration::new(1, 0));
// Make sure all subprocesses either panicked or were killed because they deadlocked
for mut c in v {
c.kill().ok();
assert!(!c.wait().unwrap().success());
}
}
}