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// Copyright (C) 2016 The Qt Company Ltd.
// Copyright (C) 2016 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qwaitcondition.h"
#include "qatomic.h"
#include "qdeadlinetimer.h"
#include "qmutex.h"
#include "qplatformdefs.h"
#include "qreadwritelock.h"
#include "qstring.h"
#include "private/qcore_unix_p.h"
#include "qreadwritelock_p.h"
#include <errno.h>
#include <sys/time.h>
#include <time.h>
QT_BEGIN_NAMESPACE
static constexpr clockid_t SteadyClockClockId =
#if !defined(CLOCK_MONOTONIC)
// we don't know how to set the monotonic clock
CLOCK_REALTIME
#elif defined(_LIBCPP_VERSION) && defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK)
// libc++ falling back to system_clock
CLOCK_REALTIME
#elif defined(__GLIBCXX__) && !defined(_GLIBCXX_USE_CLOCK_MONOTONIC)
// libstdc++ falling back to system_clock
CLOCK_REALTIME
#elif defined(Q_OS_DARWIN)
// Darwin lacks pthread_condattr_setclock()
CLOCK_REALTIME
#elif defined(Q_OS_QNX)
// unknown why
CLOCK_REALTIME
#elif defined(__GLIBCXX__) || defined(_LIBCPP_VERSION)
// both libstdc++ and libc++ do use CLOCK_MONOTONIC
CLOCK_MONOTONIC
#else
# warning "Unknown C++ Standard Library implementation - code may be sub-optimal"
CLOCK_REALTIME
#endif
;
static void qt_report_pthread_error(int code, const char *where, const char *what)
{
if (code != 0)
qErrnoWarning(code, "%s: %s failure", where, what);
}
static void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where)
{
pthread_condattr_t *attrp = nullptr;
#if defined(CLOCK_MONOTONIC) && !defined(Q_OS_DARWIN)
pthread_condattr_t condattr;
attrp = &condattr;
pthread_condattr_init(&condattr);
auto destroy = qScopeGuard([&] { pthread_condattr_destroy(&condattr); });
if (SteadyClockClockId != CLOCK_REALTIME)
pthread_condattr_setclock(&condattr, SteadyClockClockId);
#endif
qt_report_pthread_error(pthread_cond_init(cond, attrp), where, "cv init");
}
static void qt_abstime_for_timeout(timespec *ts, QDeadlineTimer deadline)
{
using namespace std::chrono;
using Clock =
std::conditional_t<SteadyClockClockId == CLOCK_REALTIME, system_clock, steady_clock>;
auto timePoint = deadline.deadline<Clock>();
*ts = durationToTimespec(timePoint.time_since_epoch());
}
class QWaitConditionPrivate
{
public:
pthread_mutex_t mutex;
pthread_cond_t cond;
int waiters;
int wakeups;
int wait_relative(QDeadlineTimer deadline)
{
timespec ti;
qt_abstime_for_timeout(&ti, deadline);
return pthread_cond_timedwait(&cond, &mutex, &ti);
}
bool wait(QDeadlineTimer deadline)
{
int code;
forever {
if (!deadline.isForever()) {
code = wait_relative(deadline);
} else {
code = pthread_cond_wait(&cond, &mutex);
}
if (code == 0 && wakeups == 0) {
// spurious wakeup
continue;
}
break;
}
Q_ASSERT_X(waiters > 0, "QWaitCondition::wait", "internal error (waiters)");
--waiters;
if (code == 0) {
Q_ASSERT_X(wakeups > 0, "QWaitCondition::wait", "internal error (wakeups)");
--wakeups;
}
qt_report_pthread_error(pthread_mutex_unlock(&mutex), "QWaitCondition::wait()",
"mutex unlock");
if (code && code != ETIMEDOUT)
qt_report_pthread_error(code, "QWaitCondition::wait()", "cv wait");
return (code == 0);
}
};
QWaitCondition::QWaitCondition()
{
d = new QWaitConditionPrivate;
qt_report_pthread_error(pthread_mutex_init(&d->mutex, nullptr), "QWaitCondition", "mutex init");
qt_initialize_pthread_cond(&d->cond, "QWaitCondition");
d->waiters = d->wakeups = 0;
}
QWaitCondition::~QWaitCondition()
{
qt_report_pthread_error(pthread_cond_destroy(&d->cond), "QWaitCondition", "cv destroy");
qt_report_pthread_error(pthread_mutex_destroy(&d->mutex), "QWaitCondition", "mutex destroy");
delete d;
}
void QWaitCondition::wakeOne()
{
qt_report_pthread_error(pthread_mutex_lock(&d->mutex), "QWaitCondition::wakeOne()",
"mutex lock");
d->wakeups = qMin(d->wakeups + 1, d->waiters);
qt_report_pthread_error(pthread_cond_signal(&d->cond), "QWaitCondition::wakeOne()",
"cv signal");
qt_report_pthread_error(pthread_mutex_unlock(&d->mutex), "QWaitCondition::wakeOne()",
"mutex unlock");
}
void QWaitCondition::wakeAll()
{
qt_report_pthread_error(pthread_mutex_lock(&d->mutex), "QWaitCondition::wakeAll()",
"mutex lock");
d->wakeups = d->waiters;
qt_report_pthread_error(pthread_cond_broadcast(&d->cond), "QWaitCondition::wakeAll()",
"cv broadcast");
qt_report_pthread_error(pthread_mutex_unlock(&d->mutex), "QWaitCondition::wakeAll()",
"mutex unlock");
}
bool QWaitCondition::wait(QMutex *mutex, unsigned long time)
{
if (time == std::numeric_limits<unsigned long>::max())
return wait(mutex, QDeadlineTimer(QDeadlineTimer::Forever));
return wait(mutex, QDeadlineTimer(time));
}
bool QWaitCondition::wait(QMutex *mutex, QDeadlineTimer deadline)
{
if (!mutex)
return false;
qt_report_pthread_error(pthread_mutex_lock(&d->mutex), "QWaitCondition::wait()", "mutex lock");
++d->waiters;
mutex->unlock();
bool returnValue = d->wait(deadline);
mutex->lock();
return returnValue;
}
bool QWaitCondition::wait(QReadWriteLock *readWriteLock, unsigned long time)
{
if (time == std::numeric_limits<unsigned long>::max())
return wait(readWriteLock, QDeadlineTimer(QDeadlineTimer::Forever));
return wait(readWriteLock, QDeadlineTimer(time));
}
bool QWaitCondition::wait(QReadWriteLock *readWriteLock, QDeadlineTimer deadline)
{
using namespace QReadWriteLockStates;
if (!readWriteLock)
return false;
auto previousState = QReadWriteLockPrivate::stateForWaitCondition(readWriteLock);
if (previousState == Unlocked)
return false;
if (previousState == RecursivelyLocked) {
qWarning("QWaitCondition: cannot wait on QReadWriteLocks with recursive lockForWrite()");
return false;
}
qt_report_pthread_error(pthread_mutex_lock(&d->mutex), "QWaitCondition::wait()", "mutex lock");
++d->waiters;
readWriteLock->unlock();
bool returnValue = d->wait(deadline);
if (previousState == LockedForWrite)
readWriteLock->lockForWrite();
else
readWriteLock->lockForRead();
return returnValue;
}
QT_END_NAMESPACE
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