diff -r d87633b62f1f -r 47bc06170313 src/hotspot/os/linux/waitBarrier_linux.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/hotspot/os/linux/waitBarrier_linux.cpp Fri Jan 11 10:58:46 2019 +0100 @@ -0,0 +1,80 @@ +/* + * Copyright (c) 2019, 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, "Should not be already armed: " + "_futex_barrier=%d", _futex_barrier); + _futex_barrier = barrier_tag; + OrderAccess::fence(); +} + +void LinuxWaitBarrier::disarm() { + assert(_futex_barrier != 0, "Should be armed/non-zero."); + _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 failed"); +} + +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 failed"); + // 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); +}