134 lines
2.8 KiB
C++
134 lines
2.8 KiB
C++
/*
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* Copyright (C) 2010-2014 Paul Davis <paul@linuxaudiosystems.com>
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* Copyright (C) 2015-2017 Robin Gareus <robin@gareus.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "pbd/semutils.h"
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#include "pbd/failed_constructor.h"
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#ifdef USE_FUTEX_SEMAPHORE
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#include <errno.h>
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#include <linux/futex.h>
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#include <sched.h>
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#include <syscall.h>
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#include <unistd.h>
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#endif
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using namespace PBD;
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Semaphore::Semaphore (const char* name, int val)
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{
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#ifdef WINDOWS_SEMAPHORE
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(void) name; /* stop warning */
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if ((_sem = CreateSemaphore(NULL, val, 32767, NULL)) == NULL) {
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throw failed_constructor ();
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}
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#elif __APPLE__
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if ((_sem = sem_open (name, O_CREAT, 0600, val)) == (sem_t*) SEM_FAILED) {
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throw failed_constructor ();
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}
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/* this semaphore does not exist for IPC */
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if (sem_unlink (name)) {
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throw failed_constructor ();
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}
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#elif defined USE_FUTEX_SEMAPHORE
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(void)name; /* stop warning */
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_value = val;
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_futex = 0;
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#else
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(void) name; /* stop gcc warning on !Apple systems */
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if (sem_init (&_sem, 0, val)) {
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throw failed_constructor ();
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}
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#endif
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}
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Semaphore::~Semaphore ()
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{
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#ifdef WINDOWS_SEMAPHORE
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CloseHandle(_sem);
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#elif __APPLE__
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sem_close (ptr_to_sem());
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#endif
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}
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#ifdef WINDOWS_SEMAPHORE
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int
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Semaphore::signal ()
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{
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// non-zero on success, opposite to posix
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return !ReleaseSemaphore(_sem, 1, NULL);
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}
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int
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Semaphore::wait ()
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{
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DWORD result = 0;
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result = WaitForSingleObject(_sem, INFINITE);
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return (result == WAIT_OBJECT_0 ? 0 : -1);
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}
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int
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Semaphore::reset ()
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{
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int rv = -1;
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DWORD result;
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do {
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++rv;
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result = WaitForSingleObject(_sem, 0);
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} while (result == WAIT_OBJECT_0);
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return rv;
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}
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#elif defined USE_FUTEX_SEMAPHORE
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int
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Semaphore::signal ()
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{
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if (std::atomic_fetch_add_explicit (&_value, 1, std::memory_order_relaxed) < 0) {
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while (syscall (SYS_futex, &_futex, FUTEX_WAKE_PRIVATE, 1, NULL, NULL, 0) < 1) {
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sched_yield();
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}
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}
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return 0;
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}
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int
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Semaphore::wait ()
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{
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if (std::atomic_fetch_sub_explicit (&_value, 1, std::memory_order_relaxed) <= 0) {
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syscall(SYS_futex, &_futex, FUTEX_WAIT_PRIVATE, _futex, NULL, NULL, 0);
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}
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return 0;
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}
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int
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Semaphore::reset ()
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{
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int value = _value;
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_value = 0;
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return value;
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}
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#endif
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