| // futex -*- C++ -*- |
| |
| // Copyright (C) 2015-2017 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library 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 for more details. |
| |
| // Under Section 7 of GPL version 3, you are granted additional |
| // permissions described in the GCC Runtime Library Exception, version |
| // 3.1, as published by the Free Software Foundation. |
| |
| // You should have received a copy of the GNU General Public License and |
| // a copy of the GCC Runtime Library Exception along with this program; |
| // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| // <http://www.gnu.org/licenses/>. |
| |
| #include <bits/atomic_futex.h> |
| #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) |
| #if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1 |
| #include <chrono> |
| #include <climits> |
| #include <syscall.h> |
| #include <unistd.h> |
| #include <sys/time.h> |
| #include <errno.h> |
| #include <debug/debug.h> |
| |
| // Constants for the wait/wake futex syscall operations |
| const unsigned futex_wait_op = 0; |
| const unsigned futex_wake_op = 1; |
| |
| namespace std _GLIBCXX_VISIBILITY(default) |
| { |
| _GLIBCXX_BEGIN_NAMESPACE_VERSION |
| |
| bool |
| __atomic_futex_unsigned_base::_M_futex_wait_until(unsigned *__addr, |
| unsigned __val, |
| bool __has_timeout, chrono::seconds __s, chrono::nanoseconds __ns) |
| { |
| if (!__has_timeout) |
| { |
| // Ignore whether we actually succeeded to block because at worst, |
| // we will fall back to spin-waiting. The only thing we could do |
| // here on errors is abort. |
| int ret __attribute__((unused)); |
| ret = syscall (SYS_futex, __addr, futex_wait_op, __val, nullptr); |
| _GLIBCXX_DEBUG_ASSERT(ret == 0 || errno == EINTR || errno == EAGAIN); |
| return true; |
| } |
| else |
| { |
| struct timeval tv; |
| gettimeofday (&tv, NULL); |
| // Convert the absolute timeout value to a relative timeout |
| struct timespec rt; |
| rt.tv_sec = __s.count() - tv.tv_sec; |
| rt.tv_nsec = __ns.count() - tv.tv_usec * 1000; |
| if (rt.tv_nsec < 0) |
| { |
| rt.tv_nsec += 1000000000; |
| --rt.tv_sec; |
| } |
| // Did we already time out? |
| if (rt.tv_sec < 0) |
| return false; |
| |
| if (syscall (SYS_futex, __addr, futex_wait_op, __val, &rt) == -1) |
| { |
| _GLIBCXX_DEBUG_ASSERT(errno == EINTR || errno == EAGAIN |
| || errno == ETIMEDOUT); |
| if (errno == ETIMEDOUT) |
| return false; |
| } |
| return true; |
| } |
| } |
| |
| void |
| __atomic_futex_unsigned_base::_M_futex_notify_all(unsigned* __addr) |
| { |
| // This syscall can fail for various reasons, including in situations |
| // in which there is no real error. Thus, we don't bother checking |
| // the error codes. See the futex documentation and glibc for background. |
| syscall (SYS_futex, __addr, futex_wake_op, INT_MAX); |
| } |
| |
| _GLIBCXX_END_NAMESPACE_VERSION |
| } |
| #endif |
| #endif |