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// futex -*- C++ -*-
// Copyright (C) 2015-2016 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
#include <bits/atomic_futex.h>
#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
#if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1
#include <chrono>
#include <climits>
#include <syscall.h>
#include <unistd.h>
#include <sys/time.h>
#include <errno.h>
#include <debug/debug.h>
// Constants for the wait/wake futex syscall operations
const unsigned futex_wait_op = 0;
const unsigned futex_wake_op = 1;
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
bool
__atomic_futex_unsigned_base::_M_futex_wait_until(unsigned *__addr,
unsigned __val,
bool __has_timeout, chrono::seconds __s, chrono::nanoseconds __ns)
{
if (!__has_timeout)
{
// Ignore whether we actually succeeded to block because at worst,
// we will fall back to spin-waiting. The only thing we could do
// here on errors is abort.
int ret __attribute__((unused));
ret = syscall (SYS_futex, __addr, futex_wait_op, __val, nullptr);
_GLIBCXX_DEBUG_ASSERT(ret == 0 || errno == EINTR || errno == EAGAIN);
return true;
}
else
{
struct timeval tv;
gettimeofday (&tv, NULL);
// Convert the absolute timeout value to a relative timeout
struct timespec rt;
rt.tv_sec = __s.count() - tv.tv_sec;
rt.tv_nsec = __ns.count() - tv.tv_usec * 1000;
if (rt.tv_nsec < 0)
{
rt.tv_nsec += 1000000000;
--rt.tv_sec;
}
// Did we already time out?
if (rt.tv_sec < 0)
return false;
if (syscall (SYS_futex, __addr, futex_wait_op, __val, &rt) == -1)
{
_GLIBCXX_DEBUG_ASSERT(errno == EINTR || errno == EAGAIN
|| errno == ETIMEDOUT);
if (errno == ETIMEDOUT)
return false;
}
return true;
}
}
void
__atomic_futex_unsigned_base::_M_futex_notify_all(unsigned* __addr)
{
// This syscall can fail for various reasons, including in situations
// in which there is no real error. Thus, we don't bother checking
// the error codes. See the futex documentation and glibc for background.
syscall (SYS_futex, __addr, futex_wake_op, INT_MAX);
}
_GLIBCXX_END_NAMESPACE_VERSION
}
#endif
#endif
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