summaryrefslogtreecommitdiffstats
path: root/src/tools/qwaitcondition_unix.cpp
blob: 5c4e9388d4ef246c3e49b1630b7378d60698af80 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
/****************************************************************************
**
** TQWaitCondition 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;

#include "qwaitcondition.h"
#include "qmutex.h"
#include "qmutex_p.h"

#include <errno.h>
#include <string.h>


struct TQWaitConditionPrivate {
    pthread_cond_t cond;
};


/*!
    \class TQWaitCondition qwaitcondition.h
    \threadsafe
    \brief The TQWaitCondition class allows waiting/waking for conditions between threads.

    \ingroup thread
    \ingroup environment

    TQWaitConditions allow a thread to tell other threads that some
    sort of condition has been met; one or many threads can block
    waiting for a TQWaitCondition to set a condition with wakeOne() or
    wakeAll(). Use wakeOne() to wake one randomly selected event or
    wakeAll() to wake them all. For example, say we have three tasks
    that should be performed every time the user presses a key; each
    task could be split into a thread, each of which would have a
    run() body like this:

    \code
    TQWaitCondition key_pressed;

    for (;;) {
	key_pressed.wait(); // This is a TQWaitCondition global variable
	// Key was pressed, do something interesting
	do_something();
    }
    \endcode

    A fourth thread would read key presses and wake the other three
    threads up every time it receives one, like this:

    \code
    TQWaitCondition key_pressed;

    for (;;) {
	getchar();
	// Causes any thread in key_pressed.wait() to return from
	// that method and continue processing
	key_pressed.wakeAll();
    }
    \endcode

    Note that the order the three threads are woken up in is
    undefined, and that if some or all of the threads are still in
    do_something() when the key is pressed, they won't be woken up
    (since they're not waiting on the condition variable) and so the
    task will not be performed for that key press. This can be
    avoided by, for example, doing something like this:

    \code
    TQMutex mymutex;
    TQWaitCondition key_pressed;
    int mycount=0;

    // Worker thread code
    for (;;) {
	key_pressed.wait(); // This is a TQWaitCondition global variable
	mymutex.lock();
	mycount++;
	mymutex.unlock();
	do_something();
	mymutex.lock();
	mycount--;
	mymutex.unlock();
    }

    // Key reading thread code
    for (;;) {
	getchar();
	mymutex.lock();
	// Sleep until there are no busy worker threads
	while( mycount > 0 ) {
	    mymutex.unlock();
	    sleep( 1 );
	    mymutex.lock();
	}
	mymutex.unlock();
	key_pressed.wakeAll();
    }
    \endcode

    The mutexes are necessary because the results of two threads
    attempting to change the value of the same variable simultaneously
    are unpredictable.
*/

/*!
    Constructs a new event signalling, i.e. wait condition, object.
*/
TQWaitCondition::TQWaitCondition()
{
    d = new TQWaitConditionPrivate;

    int ret = pthread_cond_init(&d->cond, NULL);

#ifdef QT_CHECK_RANGE
    if (ret)
	qWarning( "Wait condition init failure: %s", strerror( ret ) );
#endif
}


/*!
    Deletes the event signalling, i.e. wait condition, object.
*/
TQWaitCondition::~TQWaitCondition()
{
    int ret = pthread_cond_destroy(&d->cond);

    if (ret) {
#ifdef QT_CHECK_RANGE
	qWarning( "Wait condition destroy failure: %s", strerror( ret ) );
#endif

	// seems we have threads waiting on us, lets wake them up
	pthread_cond_broadcast(&d->cond);
    }

    delete d;
}

/*!
    This wakes one thread waiting on the TQWaitCondition. The thread
    that is woken up depends on the operating system's scheduling
    policies, and cannot be controlled or predicted.

    \sa wakeAll()
*/
void TQWaitCondition::wakeOne()
{
    int ret = pthread_cond_signal(&d->cond);

#ifdef QT_CHECK_RANGE
    if (ret)
	qWarning("Wait condition wakeOne failure: %s", strerror(ret));
#endif
}

/*!
    This wakes all threads waiting on the TQWaitCondition. The order in
    which the threads are woken up depends on the operating system's
    scheduling policies, and cannot be controlled or predicted.

    \sa wakeOne()
*/
void TQWaitCondition::wakeAll()
{
    int ret = pthread_cond_broadcast(&d->cond);

#ifdef QT_CHECK_RANGE
    if (ret)
	qWarning("Wait condition wakeAll failure: %s", strerror(ret));
#endif
}

/*!
    Wait on the thread event object. The thread calling this will
    block until either of these conditions is met:
    \list
    \i Another thread signals it using wakeOne() or wakeAll(). This
       function will return TRUE in this case.
    \i \a time milliseconds has elapsed. If \a time is ULONG_MAX (the
       default), then the wait will never timeout (the event must be
       signalled). This function will return FALSE if the wait timed
       out.
    \endlist

    \sa wakeOne(), wakeAll()
*/
bool TQWaitCondition::wait(unsigned long time)
{
    static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
    pthread_mutex_lock( &mutex );

    int ret;
    if (time != ULONG_MAX) {
	struct timeval tv;
	gettimeofday(&tv, 0);

	timespec ti;
	ti.tv_nsec = ( tv.tv_usec + ( time % 1000 ) * 1000 ) * 1000;
	ti.tv_sec = tv.tv_sec + (time / 1000) + ( ti.tv_nsec / 1000000000 );
	ti.tv_nsec %= 1000000000;

	ret = pthread_cond_timedwait(&d->cond, &mutex, &ti);
    } else
	ret = pthread_cond_wait(&d->cond, &mutex);

#ifdef QT_CHECK_RANGE
    if (ret && ret != ETIMEDOUT)
	qWarning("Wait condition wait failure: %s",strerror(ret));
#endif

    pthread_mutex_unlock( &mutex );

    return (ret == 0);
}

/*!
    \overload

    Release the locked \a mutex and wait on the thread event object.
    The \a mutex must be initially locked by the calling thread. If \a
    mutex is not in a locked state, this function returns immediately.
    If \a mutex is a recursive mutex, this function returns
    immediately. The \a mutex will be unlocked, and the calling thread
    will block until either of these conditions is met:
    \list
    \i Another thread signals it using wakeOne() or wakeAll(). This
       function will return TRUE in this case.
    \i \a time milliseconds has elapsed. If \a time is ULONG_MAX (the
       default), then the wait will never timeout (the event must be
       signalled). This function will return FALSE if the wait timed
       out.
    \endlist

    The mutex will be returned to the same locked state. This function
    is provided to allow the atomic transition from the locked state
    to the wait state.

    \sa wakeOne(), wakeAll()
*/
bool TQWaitCondition::wait(TQMutex *mutex, unsigned long time)
{
    if (! mutex)
	return FALSE;

    if (mutex->d->type() == Q_MUTEX_RECURSIVE) {
#ifdef QT_CHECK_RANGE
	qWarning("Wait condition warning: using recursive mutexes with\n"
		 "                        wait conditions is undefined!");
#endif
	return FALSE;
    }

    int ret;
    if (time != ULONG_MAX) {
	struct timeval tv;
	gettimeofday(&tv, 0);

	timespec ti;
	ti.tv_nsec = ( tv.tv_usec + ( time % 1000 ) * 1000 ) * 1000;
	ti.tv_sec = tv.tv_sec + (time / 1000) + ( ti.tv_nsec / 1000000000 );
	ti.tv_nsec %= 1000000000;

	ret = pthread_cond_timedwait(&d->cond, &mutex->d->handle, &ti);
    } else
	ret = pthread_cond_wait(&d->cond, &mutex->d->handle);

#ifdef QT_CHECK_RANGE
    if (ret && ret != ETIMEDOUT)
	qWarning("Wait condition wait failure: %s",strerror(ret));
#endif

    return (ret == 0);
}

#endif // QT_THREAD_SUPPORT