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80 lines
2.8 KiB
C++
80 lines
2.8 KiB
C++
/*
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* Copyright (c) 2019, 2025, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "runtime/orderAccess.hpp"
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#include "runtime/os.hpp"
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#include "utilities/debug.hpp"
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#include "waitBarrier_linux.hpp"
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#include <linux/futex.h>
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#include <sys/syscall.h>
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// 32-bit RISC-V has no SYS_futex syscall.
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#ifdef RISCV32
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#if !defined(SYS_futex) && defined(SYS_futex_time64)
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#define SYS_futex SYS_futex_time64
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#endif
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#endif
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static long futex(volatile int *addr, int futex_op, int op_arg) {
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return syscall(SYS_futex, addr, futex_op, op_arg, nullptr, nullptr, 0);
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}
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void LinuxWaitBarrier::arm(int barrier_tag) {
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assert(_futex_barrier == 0, "Should not be already armed: "
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"_futex_barrier=%d", _futex_barrier);
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_futex_barrier = barrier_tag;
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OrderAccess::fence();
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}
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void LinuxWaitBarrier::disarm() {
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assert(_futex_barrier != 0, "Should be armed/non-zero.");
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_futex_barrier = 0;
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long s = futex(&_futex_barrier,
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FUTEX_WAKE_PRIVATE,
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INT_MAX /* wake a max of this many threads */);
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guarantee_with_errno(s > -1, "futex FUTEX_WAKE failed");
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}
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void LinuxWaitBarrier::wait(int barrier_tag) {
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assert(barrier_tag != 0, "Trying to wait on disarmed value");
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if (barrier_tag == 0 ||
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barrier_tag != _futex_barrier) {
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OrderAccess::fence();
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return;
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}
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do {
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long s = futex(&_futex_barrier,
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FUTEX_WAIT_PRIVATE,
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barrier_tag /* should be this tag */);
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guarantee_with_errno((s == 0) ||
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(s == -1 && errno == EAGAIN) ||
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(s == -1 && errno == EINTR),
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"futex FUTEX_WAIT failed");
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// Return value 0: woken up, but re-check in case of spurious wakeup.
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// Error EINTR: woken by signal, so re-check and re-wait if necessary.
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// Error EAGAIN: we are already disarmed and so will pass the check.
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} while (barrier_tag == _futex_barrier);
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}
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