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rocksdb/thrift/lib/cpp/concurrency/Mutex.h

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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
#ifndef THRIFT_CONCURRENCY_MUTEX_H_
#define THRIFT_CONCURRENCY_MUTEX_H_ 1
#include <boost/shared_ptr.hpp>
#include <boost/noncopyable.hpp>
namespace apache { namespace thrift { namespace concurrency {
#ifndef THRIFT_NO_CONTENTION_PROFILING
/**
* Determines if the Thrift Mutex and ReadWriteMutex classes will attempt to
* profile their blocking acquire methods. If this value is set to non-zero,
* Thrift will attempt to invoke the callback once every profilingSampleRate
* times. However, as the sampling is not synchronized the rate is not
* guaranteed, and could be subject to big bursts and swings. Please ensure
* your sampling callback is as performant as your application requires.
*
* The callback will get called with the wait time taken to lock the mutex in
* usec and a (void*) that uniquely identifies the Mutex (or ReadWriteMutex)
* being locked.
*
* The enableMutexProfiling() function is unsynchronized; calling this function
* while profiling is already enabled may result in race conditions. On
* architectures where a pointer assignment is atomic, this is safe but there
* is no guarantee threads will agree on a single callback within any
* particular time period.
*/
typedef void (*MutexWaitCallback)(const void* id, int64_t waitTimeMicros);
void enableMutexProfiling(int32_t profilingSampleRate,
MutexWaitCallback callback);
#endif
/**
* A simple mutex class
*
* @version $Id:$
*/
class Mutex {
public:
typedef void (*Initializer)(void*);
// Specifying the type of the mutex with one of the static Initializer
// methods defined in this class.
explicit Mutex(Initializer init = DEFAULT_INITIALIZER);
// Specifying the type of the mutex with an integer. The value has
// to be supported by the underlying implementation, currently
// pthread_mutex. So the possible values are PTHREAD_MUTEX_NORMAL,
// PTHREAD_MUTEX_ERRORCHECK, PTHREAD_MUTEX_RECURSIVE and
// PTHREAD_MUTEX_DEFAULT.
explicit Mutex(int type);
virtual ~Mutex() {}
virtual void lock() const;
virtual bool trylock() const;
virtual bool timedlock(int64_t milliseconds) const;
virtual void unlock() const;
/**
* Determine if the mutex is locked.
*
* This is intended to be used primarily as a debugging aid, and is not
* guaranteed to be a fast operation. For example, a common use case is to
* assert(mutex.isLocked()) in functions that may only be called with a
* particular mutex already locked.
*
* TODO: This method currently always returns false for recursive mutexes.
* Avoid calling this method on recursive mutexes.
*/
virtual bool isLocked() const;
void* getUnderlyingImpl() const;
static void DEFAULT_INITIALIZER(void*);
static void ADAPTIVE_INITIALIZER(void*);
static void RECURSIVE_INITIALIZER(void*);
private:
class impl;
boost::shared_ptr<impl> impl_;
};
class ReadWriteMutex {
public:
ReadWriteMutex();
virtual ~ReadWriteMutex() {}
// these get the lock and block until it is done successfully
virtual void acquireRead() const;
virtual void acquireWrite() const;
// these get the lock and block until it is done successfully
// or run out of time
virtual bool timedRead(int64_t milliseconds) const;
virtual bool timedWrite(int64_t milliseconds) const;
// these attempt to get the lock, returning false immediately if they fail
virtual bool attemptRead() const;
virtual bool attemptWrite() const;
// this releases both read and write locks
virtual void release() const;
private:
class impl;
boost::shared_ptr<impl> impl_;
};
/**
* A ReadWriteMutex that guarantees writers will not be starved by readers:
* When a writer attempts to acquire the mutex, all new readers will be
* blocked from acquiring the mutex until the writer has acquired and
* released it. In some operating systems, this may already be guaranteed
* by a regular ReadWriteMutex.
*/
class NoStarveReadWriteMutex : public ReadWriteMutex {
public:
NoStarveReadWriteMutex();
virtual void acquireRead() const;
virtual void acquireWrite() const;
// these get the lock and block until it is done successfully
// or run out of time
virtual bool timedRead(int64_t milliseconds) const;
virtual bool timedWrite(int64_t milliseconds) const;
private:
Mutex mutex_;
mutable volatile bool writerWaiting_;
};
class Guard : boost::noncopyable {
public:
explicit Guard(const Mutex& value, int64_t timeout = 0) : mutex_(&value) {
if (timeout == 0) {
value.lock();
} else if (timeout < 0) {
if (!value.trylock()) {
mutex_ = NULL;
}
} else {
if (!value.timedlock(timeout)) {
mutex_ = NULL;
}
}
}
~Guard() {
if (mutex_) {
mutex_->unlock();
}
}
/*
* This is really operator bool. However, implementing it to return
* bool is actually harmful. See
* www.artima.com/cppsource/safebool.html for the details; in brief,
* converting to bool allows a lot of nonsensical operations in
* addition to simple testing. To avoid that, we return a pointer to
* member which can only be used for testing.
*/
typedef const Mutex*const Guard::*const pBoolMember;
inline operator pBoolMember() const {
return mutex_ != NULL ? &Guard::mutex_ : NULL;
}
private:
const Mutex* mutex_;
};
// Can be used as second argument to RWGuard to make code more readable
// as to whether we're doing acquireRead() or acquireWrite().
enum RWGuardType {
RW_READ = 0,
RW_WRITE = 1,
};
class RWGuard : boost::noncopyable {
public:
explicit RWGuard(const ReadWriteMutex& value, bool write = false,
int64_t timeout=0)
: rw_mutex_(value), locked_(true) {
if (write) {
if (timeout) {
locked_ = rw_mutex_.timedWrite(timeout);
} else {
rw_mutex_.acquireWrite();
}
} else {
if (timeout) {
locked_ = rw_mutex_.timedRead(timeout);
} else {
rw_mutex_.acquireRead();
}
}
}
RWGuard(const ReadWriteMutex& value, RWGuardType type, int64_t timeout = 0)
: rw_mutex_(value), locked_(true) {
if (type == RW_WRITE) {
if (timeout) {
locked_ = rw_mutex_.timedWrite(timeout);
} else {
rw_mutex_.acquireWrite();
}
} else {
if (timeout) {
locked_ = rw_mutex_.timedRead(timeout);
} else {
rw_mutex_.acquireRead();
}
}
}
~RWGuard() {
if (locked_) {
rw_mutex_.release();
}
}
typedef const bool RWGuard::*const pBoolMember;
operator pBoolMember() const {
return locked_ ? &RWGuard::locked_ : NULL;
}
bool operator!() const {
return !locked_;
}
bool release() {
if (!locked_) return false;
rw_mutex_.release();
locked_ = false;
return true;
}
private:
const ReadWriteMutex& rw_mutex_;
mutable bool locked_;
};
// A little hack to prevent someone from trying to do "Guard(m);"
// Such a use is invalid because the temporary Guard object is
// destroyed at the end of the line, releasing the lock.
// Sorry for polluting the global namespace, but I think it's worth it.
#define Guard(m) incorrect_use_of_Guard(m)
#define RWGuard(m) incorrect_use_of_RWGuard(m)
}}} // apache::thrift::concurrency
#endif // #ifndef THRIFT_CONCURRENCY_MUTEX_H_