/* * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code 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 * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled/precompiled.hpp" #include "runtime/orderAccess.hpp" #include "runtime/os.hpp" #include "waitBarrier_linux.hpp" #include #include #define check_with_errno(check_type, cond, msg) \ do { \ int err = errno; \ check_type(cond, "%s; error='%s' (errno=%s)", msg, os::strerror(err), \ os::errno_name(err)); \ } while (false) #define guarantee_with_errno(cond, msg) check_with_errno(guarantee, cond, msg) static int futex(volatile int *addr, int futex_op, int op_arg) { return syscall(SYS_futex, addr, futex_op, op_arg, NULL, NULL, 0); } void LinuxWaitBarrier::arm(int barrier_tag) { assert(_futex_barrier == 0, "Already armed"); _futex_barrier = barrier_tag; OrderAccess::fence(); } void LinuxWaitBarrier::wake() { assert(_futex_barrier != 0, "Not armed"); _futex_barrier = 0; int s = futex(&_futex_barrier, FUTEX_WAKE_PRIVATE, INT_MAX /* wake a max of this many threads */); guarantee_with_errno(s > -1, "futex FUTEX_WAKE"); } void LinuxWaitBarrier::wait(int barrier_tag) { assert(barrier_tag != 0, "Trying to wait on disarmed value"); if (barrier_tag == 0 || barrier_tag != _futex_barrier) { OrderAccess::fence(); return; } do { int s = futex(&_futex_barrier, FUTEX_WAIT_PRIVATE, barrier_tag /* should be this tag */); guarantee_with_errno((s == 0) || (s == -1 && errno == EAGAIN) || (s == -1 && errno == EINTR), "futex FUTEX_WAIT"); // Return value 0: woken up, but re-check in case of spurious wakeup // Error EINTR: woken by signal, so re-check and re-wait if necessary. // Error EAGAIN: we are already disarmed and so will pass the check } while (barrier_tag == _futex_barrier); }