]>
Commit | Line | Data |
---|---|---|
19a98dc4 | 1 | // futex -*- C++ -*- |
2 | ||
fbd26352 | 3 | // Copyright (C) 2015-2019 Free Software Foundation, Inc. |
19a98dc4 | 4 | // |
5 | // This file is part of the GNU ISO C++ Library. This library is free | |
6 | // software; you can redistribute it and/or modify it under the | |
7 | // terms of the GNU General Public License as published by the | |
8 | // Free Software Foundation; either version 3, or (at your option) | |
9 | // any later version. | |
10 | ||
11 | // This library is distributed in the hope that it will be useful, | |
12 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | // GNU General Public License for more details. | |
15 | ||
16 | // Under Section 7 of GPL version 3, you are granted additional | |
17 | // permissions described in the GCC Runtime Library Exception, version | |
18 | // 3.1, as published by the Free Software Foundation. | |
19 | ||
20 | // You should have received a copy of the GNU General Public License and | |
21 | // a copy of the GCC Runtime Library Exception along with this program; | |
22 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
23 | // <http://www.gnu.org/licenses/>. | |
24 | ||
19a98dc4 | 25 | #include <bits/atomic_futex.h> |
d3901223 | 26 | #ifdef _GLIBCXX_HAS_GTHREADS |
0816fa57 | 27 | #if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1 |
19a98dc4 | 28 | #include <chrono> |
29 | #include <climits> | |
30 | #include <syscall.h> | |
31 | #include <unistd.h> | |
32 | #include <sys/time.h> | |
33 | #include <errno.h> | |
34 | #include <debug/debug.h> | |
35 | ||
36 | // Constants for the wait/wake futex syscall operations | |
37 | const unsigned futex_wait_op = 0; | |
38 | const unsigned futex_wake_op = 1; | |
39 | ||
40 | namespace std _GLIBCXX_VISIBILITY(default) | |
41 | { | |
42 | _GLIBCXX_BEGIN_NAMESPACE_VERSION | |
43 | ||
44 | bool | |
45 | __atomic_futex_unsigned_base::_M_futex_wait_until(unsigned *__addr, | |
46 | unsigned __val, | |
47 | bool __has_timeout, chrono::seconds __s, chrono::nanoseconds __ns) | |
48 | { | |
49 | if (!__has_timeout) | |
50 | { | |
51 | // Ignore whether we actually succeeded to block because at worst, | |
52 | // we will fall back to spin-waiting. The only thing we could do | |
53 | // here on errors is abort. | |
54 | int ret __attribute__((unused)); | |
93425970 | 55 | ret = syscall (SYS_futex, __addr, futex_wait_op, __val, nullptr); |
e700cae5 | 56 | __glibcxx_assert(ret == 0 || errno == EINTR || errno == EAGAIN); |
19a98dc4 | 57 | return true; |
58 | } | |
59 | else | |
60 | { | |
61 | struct timeval tv; | |
62 | gettimeofday (&tv, NULL); | |
63 | // Convert the absolute timeout value to a relative timeout | |
64 | struct timespec rt; | |
65 | rt.tv_sec = __s.count() - tv.tv_sec; | |
66 | rt.tv_nsec = __ns.count() - tv.tv_usec * 1000; | |
67 | if (rt.tv_nsec < 0) | |
68 | { | |
69 | rt.tv_nsec += 1000000000; | |
70 | --rt.tv_sec; | |
71 | } | |
72 | // Did we already time out? | |
73 | if (rt.tv_sec < 0) | |
74 | return false; | |
75 | ||
76 | if (syscall (SYS_futex, __addr, futex_wait_op, __val, &rt) == -1) | |
77 | { | |
e700cae5 | 78 | __glibcxx_assert(errno == EINTR || errno == EAGAIN |
79 | || errno == ETIMEDOUT); | |
19a98dc4 | 80 | if (errno == ETIMEDOUT) |
81 | return false; | |
82 | } | |
83 | return true; | |
84 | } | |
85 | } | |
86 | ||
87 | void | |
88 | __atomic_futex_unsigned_base::_M_futex_notify_all(unsigned* __addr) | |
89 | { | |
90 | // This syscall can fail for various reasons, including in situations | |
91 | // in which there is no real error. Thus, we don't bother checking | |
92 | // the error codes. See the futex documentation and glibc for background. | |
93 | syscall (SYS_futex, __addr, futex_wake_op, INT_MAX); | |
94 | } | |
95 | ||
30915773 | 96 | _GLIBCXX_END_NAMESPACE_VERSION |
19a98dc4 | 97 | } |
d3901223 | 98 | #endif // defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1 |
99 | #endif // _GLIBCXX_HAS_GTHREADS |