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/*
* Copyright (c) 2013, Ford Motor Company
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following
* disclaimer in the documentation and/or other materials provided with the
* distribution.
*
* Neither the name of the Ford Motor Company nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SRC_COMPONENTS_INCLUDE_UTILS_LOCK_H_
#define SRC_COMPONENTS_INCLUDE_UTILS_LOCK_H_
#if defined(OS_POSIX)
#include <pthread.h>
#include <sched.h>
#else
#error Please implement lock for your OS
#endif
#include <stdint.h>
#include "utils/macro.h"
#include "utils/atomic.h"
#include "utils/memory_barrier.h"
namespace sync_primitives {
namespace impl {
#if defined(OS_POSIX)
typedef pthread_mutex_t PlatformMutex;
#endif
} // namespace impl
class SpinMutex {
public:
SpinMutex() : state_(0) {}
void Lock() {
// Comment below add exception for lint error
// Reason: FlexeLint doesn't know about compiler's built-in instructions
/*lint -e1055*/
if (atomic_post_set(&state_) == 0) {
return;
}
for (;;) {
sched_yield();
/*lint -e1055*/
if (state_ == 0 && atomic_post_set(&state_) == 0) {
return;
}
}
}
void Unlock() {
state_ = 0;
}
~SpinMutex() {}
private:
volatile unsigned int state_;
};
/* Platform-indepenednt NON-RECURSIVE lock (mutex) wrapper
Please use AutoLock to ackquire and (automatically) release it
It eases balancing of multple lock taking/releasing and makes it
Impossible to forget to release the lock:
...
ConcurentlyAccessedData data_;
sync_primitives::Lock data_lock_;
...
{
sync_primitives::AutoLock auto_lock(data_lock_);
data_.ReadOrWriteData();
} // lock is automatically released here
*/
class Lock {
public:
Lock();
Lock(bool is_recursive);
~Lock();
// Ackquire the lock. Must be called only once on a thread.
// Please consider using AutoLock to capture it.
void Acquire();
// Release the lock. Must be called only once on a thread after lock.
// was acquired. Please consider using AutoLock to automatically release
// the lock
void Release();
// Try if lock can be captured and lock it if it was possible.
// If it captured, lock must be manually released calling to Release
// when protected resource access was finished.
// @returns wether lock was captured.
bool Try();
private:
impl::PlatformMutex mutex_;
#ifndef NDEBUG
/**
* @brief Basic debugging aid, a flag that signals wether this lock is
* currently taken
* Allows detection of abandoned and recursively captured mutexes
*/
uint32_t lock_taken_;
/**
* @brief Describe if mutex is recurcive or not
*/
bool is_mutex_recursive_;
void AssertFreeAndMarkTaken();
void AssertTakenAndMarkFree();
#else
void AssertFreeAndMarkTaken() {}
void AssertTakenAndMarkFree() {}
#endif
void Init(bool is_recursive);
friend class ConditionalVariable;
DISALLOW_COPY_AND_ASSIGN(Lock);
};
// This class is used to automatically acquire and release the a lock
class AutoLock {
public:
explicit AutoLock(Lock& lock) : lock_(lock) {
lock_.Acquire();
}
~AutoLock() {
lock_.Release();
}
private:
Lock& GetLock() {
return lock_;
}
Lock& lock_;
private:
friend class AutoUnlock;
friend class ConditionalVariable;
DISALLOW_COPY_AND_ASSIGN(AutoLock);
};
// This class is used to temporarly unlock autolocked lock
class AutoUnlock {
public:
explicit AutoUnlock(AutoLock& lock) : lock_(lock.GetLock()) {
lock_.Release();
}
~AutoUnlock() {
lock_.Acquire();
}
private:
Lock& lock_;
private:
DISALLOW_COPY_AND_ASSIGN(AutoUnlock);
};
} // namespace sync_primitives
#endif // SRC_COMPONENTS_INCLUDE_UTILS_LOCK_H_
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