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tqt3/src/tools/qmutex_unix.cpp

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/****************************************************************************
**
** TQMutex class for Unix
**
** Created : 20010725
**
** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
**
** This file is part of the tools module of the TQt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
** Software Foundation and appearing in the files LICENSE.GPL2
** and LICENSE.GPL3 included in the packaging of this file.
** Alternatively you may (at your option) use any later version
** of the GNU General Public License if such license has been
** publicly approved by Trolltech ASA (or its successors, if any)
** and the KDE Free TQt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** This file may be used under the terms of the Q Public License as
** defined by Trolltech ASA and appearing in the file LICENSE.TQPL
** included in the packaging of this file. Licensees holding valid TQt
** Commercial licenses may use this file in accordance with the TQt
** Commercial License Agreement provided with the Software.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
** herein.
**
**********************************************************************/
#if defined(QT_THREAD_SUPPORT)
#include "qplatformdefs.h"
typedef pthread_mutex_t Q_MUTEX_T;
// POSIX threads mutex types
#if ((defined(PTHREAD_MUTEX_RECURSIVE) && defined(PTHREAD_MUTEX_DEFAULT)) || \
defined(Q_OS_FREEBSD)) && !defined(Q_OS_UNIXWARE) && !defined(Q_OS_SOLARIS) && \
!defined(Q_OS_MAC)
// POSIX 1003.1c-1995 - We love this OS
# define Q_MUTEX_SET_TYPE(a, b) pthread_mutexattr_settype((a), (b))
# if defined(QT_CHECK_RANGE)
# define Q_NORMAL_MUTEX_TYPE PTHREAD_MUTEX_ERRORCHECK
# else
# define Q_NORMAL_MUTEX_TYPE PTHREAD_MUTEX_DEFAULT
# endif
# define Q_RECURSIVE_MUTEX_TYPE PTHREAD_MUTEX_RECURSIVE
#elif defined(MUTEX_NONRECURSIVE_NP) && defined(MUTEX_RECURSIVE_NP)
// POSIX 1003.4a pthreads draft extensions
# define Q_MUTEX_SET_TYPE(a, b) pthread_mutexattr_setkind_np((a), (b));
# define Q_NORMAL_MUTEX_TYPE MUTEX_NONRECURSIVE_NP
# define Q_RECURSIVE_MUTEX_TYPE MUTEX_RECURSIVE_NP
#else
// Unknown mutex types - skip them
# define Q_MUTEX_SET_TYPE(a, b)
# undef Q_NORMAL_MUTEX_TYPE
# undef Q_RECURSIVE_MUTEX_TYPE
#endif
#include "ntqmutex.h"
#include "qmutex_p.h"
#include <errno.h>
#include <string.h>
// Private class declarations
class TQRealMutexPrivate : public TQMutexPrivate {
public:
TQRealMutexPrivate(bool = FALSE);
void lock();
void unlock();
bool locked();
bool trylock();
int type() const;
int level();
bool recursive;
};
#ifndef Q_RECURSIVE_MUTEX_TYPE
class TQRecursiveMutexPrivate : public TQMutexPrivate
{
public:
TQRecursiveMutexPrivate();
~TQRecursiveMutexPrivate();
void lock();
void unlock();
bool locked();
bool trylock();
int type() const;
int level();
int count;
unsigned long owner;
pthread_mutex_t handle2;
};
#endif // !Q_RECURSIVE_MUTEX_TYPE
// Private class implementation
// base destructor
TQMutexPrivate::~TQMutexPrivate()
{
int ret = pthread_mutex_destroy(&handle);
#ifdef QT_CHECK_RANGE
if ( ret )
tqWarning( "Mutex destroy failure: %s", strerror( ret ) );
#endif
}
// real mutex class
TQRealMutexPrivate::TQRealMutexPrivate(bool recurs)
: recursive(recurs)
{
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
Q_MUTEX_SET_TYPE(&attr, recursive ? Q_RECURSIVE_MUTEX_TYPE : Q_NORMAL_MUTEX_TYPE);
Q_UNUSED(recursive);
int ret = pthread_mutex_init(&handle, &attr);
pthread_mutexattr_destroy(&attr);
#ifdef QT_CHECK_RANGE
if( ret )
tqWarning( "Mutex init failure: %s", strerror( ret ) );
#endif // QT_CHECK_RANGE
}
void TQRealMutexPrivate::lock()
{
int ret = pthread_mutex_lock(&handle);
#ifdef QT_CHECK_RANGE
if (ret)
tqWarning("Mutex lock failure: %s", strerror(ret));
#endif
}
void TQRealMutexPrivate::unlock()
{
int ret = pthread_mutex_unlock(&handle);
#ifdef QT_CHECK_RANGE
if (ret)
tqWarning("Mutex unlock failure: %s", strerror(ret));
#endif
}
bool TQRealMutexPrivate::locked()
{
int ret = pthread_mutex_trylock(&handle);
if (ret == EBUSY) {
return TRUE;
} else if (ret) {
#ifdef QT_CHECK_RANGE
tqWarning("Mutex locktest failure: %s", strerror(ret));
#endif
} else
pthread_mutex_unlock(&handle);
return FALSE;
}
bool TQRealMutexPrivate::trylock()
{
int ret = pthread_mutex_trylock(&handle);
if (ret == EBUSY) {
return FALSE;
} else if (ret) {
#ifdef QT_CHECK_RANGE
tqWarning("Mutex trylock failure: %s", strerror(ret));
#endif
return FALSE;
}
return TRUE;
}
int TQRealMutexPrivate::type() const
{
return recursive ? Q_MUTEX_RECURSIVE : Q_MUTEX_NORMAL;
}
int TQRealMutexPrivate::level()
{
return locked();
}
#ifndef Q_RECURSIVE_MUTEX_TYPE
TQRecursiveMutexPrivate::TQRecursiveMutexPrivate()
: count(0), owner(0)
{
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
Q_MUTEX_SET_TYPE(&attr, Q_NORMAL_MUTEX_TYPE);
int ret = pthread_mutex_init(&handle, &attr);
pthread_mutexattr_destroy(&attr);
# ifdef QT_CHECK_RANGE
if (ret)
tqWarning( "Mutex init failure: %s", strerror(ret) );
# endif
pthread_mutexattr_init(&attr);
ret = pthread_mutex_init( &handle2, &attr );
pthread_mutexattr_destroy(&attr);
# ifdef QT_CHECK_RANGE
if (ret)
tqWarning( "Mutex init failure: %s", strerror(ret) );
# endif
}
TQRecursiveMutexPrivate::~TQRecursiveMutexPrivate()
{
int ret = pthread_mutex_destroy(&handle2);
# ifdef QT_CHECK_RANGE
if (ret)
tqWarning( "Mutex destroy failure: %s", strerror(ret) );
# endif
}
void TQRecursiveMutexPrivate::lock()
{
pthread_mutex_lock(&handle2);
if (count > 0 && owner == (unsigned long) pthread_self()) {
count++;
} else {
pthread_mutex_unlock(&handle2);
pthread_mutex_lock(&handle);
pthread_mutex_lock(&handle2);
count = 1;
owner = (unsigned long) pthread_self();
}
pthread_mutex_unlock(&handle2);
}
void TQRecursiveMutexPrivate::unlock()
{
pthread_mutex_lock(&handle2);
if (owner == (unsigned long) pthread_self()) {
// do nothing if the count is already 0... to reflect the behaviour described
// in the docs
if (count && (--count) < 1) {
count = 0;
pthread_mutex_unlock(&handle);
}
} else {
#ifdef QT_CHECK_RANGE
tqWarning("TQMutex::unlock: unlock from different thread than locker");
tqWarning(" was locked by %d, unlock attempt from %d",
(int)owner, (int)pthread_self());
#endif
}
pthread_mutex_unlock(&handle2);
}
bool TQRecursiveMutexPrivate::locked()
{
pthread_mutex_lock(&handle2);
bool ret;
int code = pthread_mutex_trylock(&handle);
if (code == EBUSY) {
ret = TRUE;
} else {
#ifdef QT_CHECK_RANGE
if (code)
tqWarning("Mutex trylock failure: %s", strerror(code));
#endif
pthread_mutex_unlock(&handle);
ret = FALSE;
}
pthread_mutex_unlock(&handle2);
return ret;
}
bool TQRecursiveMutexPrivate::trylock()
{
bool ret = TRUE;
pthread_mutex_lock(&handle2);
if ( count > 0 && owner == (unsigned long) pthread_self() ) {
count++;
} else {
int code = pthread_mutex_trylock(&handle);
if (code == EBUSY) {
ret = FALSE;
} else if (code) {
#ifdef QT_CHECK_RANGE
tqWarning("Mutex trylock failure: %s", strerror(code));
#endif
ret = FALSE;
} else {
count = 1;
owner = (unsigned long) pthread_self();
}
}
pthread_mutex_unlock(&handle2);
return ret;
}
int TQRecursiveMutexPrivate::type() const
{
return Q_MUTEX_RECURSIVE;
}
int TQRecursiveMutexPrivate::level()
{
return count;
}
#endif // !Q_RECURSIVE_MUTEX_TYPE
/*!
\class TQMutex ntqmutex.h
\threadsafe
\brief The TQMutex class provides access serialization between threads.
\ingroup thread
\ingroup environment
The purpose of a TQMutex is to protect an object, data structure or
section of code so that only one thread can access it at a time
(This is similar to the Java \c synchronized keyword). For
example, say there is a method which prints a message to the user
on two lines:
\code
int number = 6;
void method1()
{
number *= 5;
number /= 4;
}
void method2()
{
number *= 3;
number /= 2;
}
\endcode
If these two methods are called in succession, the following happens:
\code
// method1()
number *= 5; // number is now 30
number /= 4; // number is now 7
// method2()
number *= 3; // nubmer is now 21
number /= 2; // number is now 10
\endcode
If these two methods are called simultaneously from two threads then the
following sequence could result:
\code
// Thread 1 calls method1()
number *= 5; // number is now 30
// Thread 2 calls method2().
//
// Most likely Thread 1 has been put to sleep by the operating
// system to allow Thread 2 to run.
number *= 3; // number is now 90
number /= 2; // number is now 45
// Thread 1 finishes executing.
number /= 4; // number is now 11, instead of 10
\endcode
If we add a mutex, we should get the result we want:
\code
TQMutex mutex;
int number = 6;
void method1()
{
mutex.lock();
number *= 5;
number /= 4;
mutex.unlock();
}
void method2()
{
mutex.lock();
number *= 3;
number /= 2;
mutex.unlock();
}
\endcode
Then only one thread can modify \c number at any given time and
the result is correct. This is a trivial example, of course, but
applies to any other case where things need to happen in a
particular sequence.
When you call lock() in a thread, other threads that try to call
lock() in the same place will block until the thread that got the
lock calls unlock(). A non-blocking alternative to lock() is
tryLock().
*/
/*!
Constructs a new mutex. The mutex is created in an unlocked state.
A recursive mutex is created if \a recursive is TRUE; a normal
mutex is created if \a recursive is FALSE (the default). With a
recursive mutex, a thread can lock the same mutex multiple times
and it will not be unlocked until a corresponding number of
unlock() calls have been made.
*/
TQMutex::TQMutex(bool recursive)
{
#ifndef Q_RECURSIVE_MUTEX_TYPE
if ( recursive )
d = new TQRecursiveMutexPrivate();
else
#endif // !Q_RECURSIVE_MUTEX_TYPE
d = new TQRealMutexPrivate(recursive);
}
/*!
Destroys the mutex.
\warning If you destroy a mutex that still holds a lock the
resultant behavior is undefined.
*/
TQMutex::~TQMutex()
{
delete d;
}
/*!
Attempt to lock the mutex. If another thread has locked the mutex
then this call will \e block until that thread has unlocked it.
\sa unlock(), locked()
*/
void TQMutex::lock()
{
d->lock();
}
/*!
Unlocks the mutex. Attempting to unlock a mutex in a different
thread to the one that locked it results in an error. Unlocking a
mutex that is not locked results in undefined behaviour (varies
between different Operating Systems' thread implementations).
\sa lock(), locked()
*/
void TQMutex::unlock()
{
d->unlock();
}
/*!
Returns TRUE if the mutex is locked by another thread; otherwise
returns FALSE.
\warning Due to differing implementations of recursive mutexes on
various platforms, calling this function from the same thread that
previously locked the mutex will return undefined results.
\sa lock(), unlock()
*/
bool TQMutex::locked()
{
return d->locked();
}
/*!
Attempt to lock the mutex. If the lock was obtained, this function
returns TRUE. If another thread has locked the mutex, this
function returns FALSE, instead of waiting for the mutex to become
available, i.e. it does not block.
If the lock was obtained, the mutex must be unlocked with unlock()
before another thread can successfully lock it.
\sa lock(), unlock(), locked()
*/
bool TQMutex::tryLock()
{
return d->trylock();
}
/*!
Returns the current lock level of the mutex.
0 means the mutex is unlocked
This method should only be called when the mutex has already been locked
by lock(), otherwise the lock level could change before the next line
of code is executed.
WARNING: Non-recursive mutexes will never exceed a lock level of 1!
\sa lock(), unlock(), locked()
*/
int TQMutex::level()
{
return d->level();
}
/*!
\class TQMutexLocker ntqmutex.h
\brief The TQMutexLocker class simplifies locking and unlocking TQMutexes.
\threadsafe
\ingroup thread
\ingroup environment
The purpose of TQMutexLocker is to simplify TQMutex locking and
unlocking. Locking and unlocking a TQMutex in complex functions and
statements or in exception handling code is error prone and
difficult to debug. TQMutexLocker should be used in such situations
to ensure that the state of the mutex is well defined and always
locked and unlocked properly.
TQMutexLocker should be created within a function where a TQMutex
needs to be locked. The mutex is locked when TQMutexLocker is
created, and unlocked when TQMutexLocker is destroyed.
For example, this complex function locks a TQMutex upon entering
the function and unlocks the mutex at all the exit points:
\code
int complexFunction( int flag )
{
mutex.lock();
int return_value = 0;
switch ( flag ) {
case 0:
case 1:
{
mutex.unlock();
return moreComplexFunction( flag );
}
case 2:
{
int status = anotherFunction();
if ( status < 0 ) {
mutex.unlock();
return -2;
}
return_value = status + flag;
break;
}
default:
{
if ( flag > 10 ) {
mutex.unlock();
return -1;
}
break;
}
}
mutex.unlock();
return return_value;
}
\endcode
This example function will get more complicated as it is
developed, which increases the likelihood that errors will occur.
Using TQMutexLocker greatly simplifies the code, and makes it more
readable:
\code
int complexFunction( int flag )
{
TQMutexLocker locker( &mutex );
int return_value = 0;
switch ( flag ) {
case 0:
case 1:
{
return moreComplexFunction( flag );
}
case 2:
{
int status = anotherFunction();
if ( status < 0 )
return -2;
return_value = status + flag;
break;
}
default:
{
if ( flag > 10 )
return -1;
break;
}
}
return return_value;
}
\endcode
Now, the mutex will always be unlocked when the TQMutexLocker
object is destroyed (when the function returns since \c locker is
an auto variable). Note that the mutex will be unlocked after
the call to moreComplexFunction() in this example, avoiding
possible bugs caused by unlocking the mutex too early, as in
the first example.
The same principle applies to code that throws and catches
exceptions. An exception that is not caught in the function that
has locked the mutex has no way of unlocking the mutex before the
exception is passed up the stack to the calling function.
TQMutexLocker also provides a mutex() member function that returns
the mutex on which the TQMutexLocker is operating. This is useful
for code that needs access to the mutex, such as
TQWaitCondition::wait(). For example:
\code
class SignalWaiter
{
private:
TQMutexLocker locker;
public:
SignalWaiter( TQMutex *mutex )
: locker( mutex )
{
}
void waitForSignal()
{
...
...
...
while ( ! signalled )
waitcondition.wait( locker.mutex() );
...
...
...
}
};
\endcode
\sa TQMutex, TQWaitCondition
*/
/*!
\fn TQMutexLocker::TQMutexLocker( TQMutex *mutex )
Constructs a TQMutexLocker and locks \a mutex. The mutex will be
unlocked when the TQMutexLocker is destroyed. If \a mutex is zero,
TQMutexLocker does nothing.
\sa TQMutex::lock()
*/
/*!
\fn TQMutexLocker::~TQMutexLocker()
Destroys the TQMutexLocker and unlocks the mutex which was locked
in the constructor.
\sa TQMutexLocker::TQMutexLocker(), TQMutex::unlock()
*/
/*!
\fn TQMutex *TQMutexLocker::mutex() const
Returns a pointer to the mutex which was locked in the
constructor.
\sa TQMutexLocker::TQMutexLocker()
*/
#endif // QT_THREAD_SUPPORT