libcruft-util/thread/event_linux.cpp

80 lines
2.1 KiB
C++

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2018 Danny Robson <danny@nerdcruft.net>
*/
#include "event.hpp"
#include "../cast.hpp"
#include "../posix/except.hpp"
#include <cerrno>
#include <linux/futex.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <limits>
using util::thread::event;
///////////////////////////////////////////////////////////////////////////////
static long
sys_futex (void *addr1, int op, int val1, struct timespec *timeout, void *addr2, int val3)
{
return syscall (SYS_futex, addr1, op | FUTEX_PRIVATE_FLAG, val1, timeout, addr2, val3);
}
///////////////////////////////////////////////////////////////////////////////
event::event ():
value (0)
{ ; }
///////////////////////////////////////////////////////////////////////////////
void
event::wait (void)
{
for (auto observed = value.load (); observed == value.load (); ) {
auto res = sys_futex (&value, FUTEX_WAIT, observed, nullptr, nullptr, 0);
if (res < 0) {
switch (errno) {
case EAGAIN: return;
case EINTR: continue;
}
posix::error::throw_code ();
}
}
}
///////////////////////////////////////////////////////////////////////////////
int
event::notify (void)
{
return notify (std::numeric_limits<int>::max ());
}
//-----------------------------------------------------------------------------
int
event::notify (int count)
{
++value;
auto res = sys_futex (&value, FUTEX_WAKE, count, nullptr, nullptr, 0);
if (res < 0)
posix::error::throw_code ();
return util::cast::narrow<int> (res);
}