From 5b5153fd5b6cc5852e4b682d1bc4a5c7979f242d Mon Sep 17 00:00:00 2001 From: Thiago Macieira Date: Thu, 17 Aug 2017 14:52:12 -0700 Subject: Move the futex implementation to a header So I can use it in QSemaphore and provide a Windows implementation. Change-Id: I6e9274c1e7444ad48c81fffd14dbc0a8e2201302 Reviewed-by: Lars Knoll --- src/corelib/thread/qfutex_p.h | 128 ++++++++++++++++++++++++++++++++++++ src/corelib/thread/qmutex_linux.cpp | 83 ++++++++++------------- src/corelib/thread/thread.pri | 1 + 3 files changed, 162 insertions(+), 50 deletions(-) create mode 100644 src/corelib/thread/qfutex_p.h diff --git a/src/corelib/thread/qfutex_p.h b/src/corelib/thread/qfutex_p.h new file mode 100644 index 0000000000..7831df81ea --- /dev/null +++ b/src/corelib/thread/qfutex_p.h @@ -0,0 +1,128 @@ +/**************************************************************************** +** +** Copyright (C) 2017 Intel Corporation. +** Contact: https://www.qt.io/licensing/ +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and The Qt Company. For licensing terms +** and conditions see https://www.qt.io/terms-conditions. For further +** information use the contact form at https://www.qt.io/contact-us. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 3 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL3 included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 3 requirements +** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 2.0 or (at your option) the GNU General +** Public license version 3 or any later version approved by the KDE Free +** Qt Foundation. The licenses are as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 +** included in the packaging of this file. Please review the following +** information to ensure the GNU General Public License requirements will +** be met: https://www.gnu.org/licenses/gpl-2.0.html and +** https://www.gnu.org/licenses/gpl-3.0.html. +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QFUTEX_P_H +#define QFUTEX_P_H + +#include + +QT_BEGIN_NAMESPACE + +namespace QtDummyFutex { + Q_DECL_CONSTEXPR inline bool futexAvailable() { return false; } + template + inline bool futexWait(Atomic &, typename Atomic::Type, int = 0) + { Q_UNREACHABLE(); return false; } + template inline void futexWakeOne(Atomic &) + { Q_UNREACHABLE(); } + template inline void futexWakeAll(Atomic &) + { Q_UNREACHABLE(); } +} + +QT_END_NAMESPACE + +#if defined(Q_OS_LINUX) && !defined(QT_LINUXBASE) +// use Linux mutexes everywhere except for LSB builds +# include +# include +# include +# include +# include +# include +# define QT_ALWAYS_USE_FUTEX + +// if not defined in linux/futex.h +# define FUTEX_PRIVATE_FLAG 128 // added in v2.6.22 + +QT_BEGIN_NAMESPACE +namespace QtLinuxFutex { + constexpr inline bool futexAvailable() { return true; } + inline int _q_futex(int *addr, int op, int val, const struct timespec *timeout) Q_DECL_NOTHROW + { + int *addr2 = 0; + int val2 = 0; + + // we use __NR_futex because some libcs (like Android's bionic) don't + // provide SYS_futex etc. + return syscall(__NR_futex, addr, op | FUTEX_PRIVATE_FLAG, val, timeout, addr2, val2); + } + template int *addr(T *ptr) + { + int *int_addr = reinterpret_cast(ptr); +#if Q_BYTE_ORDER == Q_BIG_ENDIAN + if (sizeof(T) > sizeof(int)) + int_addr++; //We want a pointer to the least significant half +#endif + return int_addr; + } + + template + inline void futexWait(Atomic &futex, typename Atomic::Type expectedValue) + { + _q_futex(addr(&futex), FUTEX_WAIT, qintptr(expectedValue), nullptr); + } + template + inline bool futexWait(Atomic &futex, typename Atomic::Type expectedValue, qint64 nstimeout) + { + struct timespec ts; + ts.tv_sec = nstimeout / 1000 / 1000 / 1000; + ts.tv_nsec = nstimeout % (1000 * 1000 * 1000); + int r = _q_futex(addr(&futex), FUTEX_WAIT, qintptr(expectedValue), &ts); + return r == 0 || errno != ETIMEDOUT; + } + template inline void futexWakeOne(Atomic &futex) + { + _q_futex(addr(&futex), FUTEX_WAKE, 1, nullptr); + } + template inline void futexWakeAll(Atomic &futex) + { + _q_futex(addr(&futex), FUTEX_WAKE, INT_MAX, nullptr); + } +} +namespace QtFutex = QtLinuxFutex; +QT_END_NAMESPACE + +#else + +QT_BEGIN_NAMESPACE +namespace QtFutex = QtDummyFutex; +QT_END_NAMESPACE +#endif + +#endif // QFUTEX_P_H diff --git a/src/corelib/thread/qmutex_linux.cpp b/src/corelib/thread/qmutex_linux.cpp index 5f6e74ac6f..d3d97ea108 100644 --- a/src/corelib/thread/qmutex_linux.cpp +++ b/src/corelib/thread/qmutex_linux.cpp @@ -44,15 +44,9 @@ #ifndef QT_NO_THREAD #include "qatomic.h" #include "qmutex_p.h" -#include "qelapsedtimer.h" +#include "qfutex_p.h" -#include -#include -#include -#include -#include - -#ifndef QT_LINUX_FUTEX +#ifndef QT_ALWAYS_USE_FUTEX # error "Qt build is broken: qmutex_linux.cpp is being built but futex support is not wanted" #endif @@ -63,6 +57,8 @@ QT_BEGIN_NAMESPACE +using namespace QtFutex; + /* * QBasicMutex implementation on Linux with futexes * @@ -107,20 +103,6 @@ QT_BEGIN_NAMESPACE * waiting in the past. We then set the mutex to 0x0 and perform a FUTEX_WAKE. */ -static inline int _q_futex(void *addr, int op, int val, const struct timespec *timeout) Q_DECL_NOTHROW -{ - volatile int *int_addr = reinterpret_cast(addr); -#if Q_BYTE_ORDER == Q_BIG_ENDIAN && QT_POINTER_SIZE == 8 - int_addr++; //We want a pointer to the 32 least significant bit of QMutex::d -#endif - int *addr2 = 0; - int val2 = 0; - - // we use __NR_futex because some libcs (like Android's bionic) don't - // provide SYS_futex etc. - return syscall(__NR_futex, int_addr, op | FUTEX_PRIVATE_FLAG, val, timeout, addr2, val2); -} - static inline QMutexData *dummyFutexValue() { return reinterpret_cast(quintptr(3)); @@ -136,36 +118,38 @@ bool lockInternal_helper(QBasicAtomicPointer &d_ptr, int timeout = - if (timeout == 0) return false; - struct timespec ts, *pts = 0; - if (IsTimed && timeout > 0) { - ts.tv_sec = timeout / 1000; - ts.tv_nsec = (timeout % 1000) * 1000 * 1000; - } - // the mutex is locked already, set a bit indicating we're waiting - while (d_ptr.fetchAndStoreAcquire(dummyFutexValue()) != 0) { - if (IsTimed && pts == &ts) { - // recalculate the timeout - qint64 xtimeout = qint64(timeout) * 1000 * 1000; - xtimeout -= elapsedTimer->nsecsElapsed(); - if (xtimeout <= 0) { - // timer expired after we returned - return false; - } - ts.tv_sec = xtimeout / Q_INT64_C(1000) / 1000 / 1000; - ts.tv_nsec = xtimeout % (Q_INT64_C(1000) * 1000 * 1000); - } - if (IsTimed && timeout > 0) - pts = &ts; + if (d_ptr.fetchAndStoreAcquire(dummyFutexValue()) == nullptr) + return true; + qint64 nstimeout = timeout * Q_INT64_C(1000) * 1000; + qint64 remainingTime = nstimeout; + forever { // successfully set the waiting bit, now sleep - int r = _q_futex(&d_ptr, FUTEX_WAIT, quintptr(dummyFutexValue()), pts); - if (IsTimed && r != 0 && errno == ETIMEDOUT) - return false; + if (IsTimed && nstimeout >= 0) { + bool r = futexWait(d_ptr, dummyFutexValue(), remainingTime); + if (!r) + return false; + + // we got woken up, so try to acquire the mutex + // note we must set to dummyFutexValue because there could be other threads + // also waiting + if (d_ptr.fetchAndStoreAcquire(dummyFutexValue()) == nullptr) + return true; - // we got woken up, so try to acquire the mutex - // note we must set to dummyFutexValue because there could be other threads - // also waiting + // recalculate the timeout + remainingTime = nstimeout - elapsedTimer->nsecsElapsed(); + if (remainingTime <= 0) + return false; + } else { + futexWait(d_ptr, dummyFutexValue()); + + // we got woken up, so try to acquire the mutex + // note we must set to dummyFutexValue because there could be other threads + // also waiting + if (d_ptr.fetchAndStoreAcquire(dummyFutexValue()) == nullptr) + return true; + } } Q_ASSERT(d_ptr.load()); @@ -195,10 +179,9 @@ void QBasicMutex::unlockInternal() Q_DECL_NOTHROW Q_ASSERT(!isRecursive()); d_ptr.storeRelease(0); - _q_futex(&d_ptr, FUTEX_WAKE, 1, 0); + futexWakeOne(d_ptr); } - QT_END_NAMESPACE #endif // QT_NO_THREAD diff --git a/src/corelib/thread/thread.pri b/src/corelib/thread/thread.pri index 0a989cfcaf..a4cb2478c6 100644 --- a/src/corelib/thread/thread.pri +++ b/src/corelib/thread/thread.pri @@ -22,6 +22,7 @@ HEADERS += thread/qmutex.h \ # private headers HEADERS += thread/qmutex_p.h \ thread/qmutexpool_p.h \ + thread/qfutex_p.h \ thread/qfutureinterface_p.h \ thread/qfuturewatcher_p.h \ thread/qorderedmutexlocker_p.h \ -- cgit v1.2.3