83 lines
2.1 KiB
C++
83 lines
2.1 KiB
C++
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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2018 Danny Robson <danny@nerdcruft.net>
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*/
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#include "flag.hpp"
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#include "../cast.hpp"
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#include <cerrno>
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#include <linux/futex.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <cruft/util/posix/except.hpp>
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#include <limits>
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using util::job::flag;
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///////////////////////////////////////////////////////////////////////////////
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static long
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sys_futex (void *addr1, int op, int val1, struct timespec *timeout, void *addr2, int val3)
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{
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return syscall (SYS_futex, addr1, op | FUTEX_PRIVATE_FLAG, val1, timeout, addr2, val3);
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}
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///////////////////////////////////////////////////////////////////////////////
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flag::flag ():
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value (0)
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{ ; }
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///////////////////////////////////////////////////////////////////////////////
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void
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flag::wait (void)
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{
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if (value)
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return;
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while (!value) {
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auto res = sys_futex (&value, FUTEX_WAIT, 0, nullptr, nullptr, 0);
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if (res < 0) {
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switch (errno) {
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case EAGAIN: return;
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case EINTR: continue;
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}
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posix::error::throw_code ();
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}
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}
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}
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///////////////////////////////////////////////////////////////////////////////
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int
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flag::notify (void)
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{
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return notify (std::numeric_limits<int>::max ());
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}
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//-----------------------------------------------------------------------------
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int
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flag::notify (int count)
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{
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value = 1;
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auto res = sys_futex (&value, FUTEX_WAKE, count, nullptr, nullptr, 0);
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if (res < 0)
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posix::error::throw_code ();
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return util::cast::narrow<int> (res);
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}
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