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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/lock_impl.h"
#include <errno.h>
#include <string.h>
#include "base/logging.h"
#include "base/lock.h"
namespace base {
namespace internal {
// Determines which platforms can consider using priority inheritance locks. Use
// this define for platform code that may not compile if priority inheritance
// locks aren't available. For this platform code,
// PRIORITY_INHERITANCE_LOCKS_POSSIBLE() is a necessary but insufficient check.
// Lock::PriorityInheritanceAvailable still must be checked as the code may
// compile but the underlying platform still may not correctly support priority
// inheritance locks.
#if defined(ANDROID)
# define PRIORITY_INHERITANCE_LOCKS_POSSIBLE() 0
#else
# define PRIORITY_INHERITANCE_LOCKS_POSSIBLE() 1
#endif
LockImpl::LockImpl() {
pthread_mutexattr_t mta;
int rv = pthread_mutexattr_init(&mta);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
#if PRIORITY_INHERITANCE_LOCKS_POSSIBLE()
if (PriorityInheritanceAvailable()) {
rv = pthread_mutexattr_setprotocol(&mta, PTHREAD_PRIO_INHERIT);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
}
#endif
#ifndef NDEBUG
// In debug, setup attributes for lock error checking.
rv = pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_ERRORCHECK);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
#endif
rv = pthread_mutex_init(&native_handle_, &mta);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
rv = pthread_mutexattr_destroy(&mta);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
}
LockImpl::~LockImpl() {
int rv = pthread_mutex_destroy(&native_handle_);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
}
bool LockImpl::Try() {
int rv = pthread_mutex_trylock(&native_handle_);
DCHECK(rv == 0 || rv == EBUSY) << ". " << strerror(rv);
return rv == 0;
}
void LockImpl::Lock() {
int rv = pthread_mutex_lock(&native_handle_);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
}
void LockImpl::Unlock() {
int rv = pthread_mutex_unlock(&native_handle_);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
}
// static
bool LockImpl::PriorityInheritanceAvailable() {
#if PRIORITY_INHERITANCE_LOCKS_POSSIBLE() && defined(XP_DARWIN)
return true;
#else
// Security concerns prevent the use of priority inheritance mutexes on Linux.
// * CVE-2010-0622 - wake_futex_pi unlocks incorrect, possible DoS.
// * CVE-2012-6647 - Linux < 3.5.1, futex_wait_requeue_pi possible DoS.
// * CVE-2014-3153 - Linux <= 3.14.5, futex_requeue, privilege escalation.
//
// If the above were all addressed, we still need a runtime check to deal with
// the bug below.
// Fixed in glibc 2.17.
// Priority inheritance mutexes may deadlock with condition variables
// during recacquisition of the mutex after the condition variable is
// signalled.
return false;
#endif
}
} // namespace internal
} // namespace base