| 6554 |
serge |
1 |
// futex -*- C++ -*- |
|
|
2 |
|
|
|
3 |
// Copyright (C) 2015 Free Software Foundation, Inc. |
|
|
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 |
// . |
|
|
24 |
|
|
|
25 |
#include |
|
|
26 |
#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) |
|
|
27 |
#if defined(_GLIBCXX_HAVE_LINUX_FUTEX) && ATOMIC_INT_LOCK_FREE > 1 |
|
|
28 |
#include |
|
|
29 |
#include |
|
|
30 |
#include |
|
|
31 |
#include |
|
|
32 |
#include |
|
|
33 |
#include |
|
|
34 |
#include |
|
|
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)); |
|
|
55 |
ret = syscall (SYS_futex, __addr, futex_wait_op, __val, nullptr); |
|
|
56 |
_GLIBCXX_DEBUG_ASSERT(ret == 0 || errno == EINTR || errno == EAGAIN); |
|
|
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 |
{ |
|
|
78 |
_GLIBCXX_DEBUG_ASSERT(errno == EINTR || errno == EAGAIN |
|
|
79 |
|| errno == ETIMEDOUT); |
|
|
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 |
|
|
|
96 |
_GLIBCXX_END_NAMESPACE_VERSION |
|
|
97 |
} |
|
|
98 |
#endif |
|
|
99 |
#endif |