1/* Copyright (C) 2008-2017 Free Software Foundation, Inc.
2 Contributed by Richard Henderson <rth@redhat.com>.
3
4 This file is part of the GNU Transactional Memory Library (libitm).
5
6 Libitm is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
10
11 Libitm is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 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
25/* Provide access to the futex system call. */
26
27#include "libitm_i.h"
28#include "futex.h"
29#include <futex_bits.h>
30#include <errno.h>
31
32namespace GTM HIDDEN {
33
34#define FUTEX_WAIT 0
35#define FUTEX_WAKE 1
36#define FUTEX_PRIVATE_FLAG 128
37
38
39static int gtm_futex_wait = FUTEX_WAIT | FUTEX_PRIVATE_FLAG;
40static int gtm_futex_wake = FUTEX_WAKE | FUTEX_PRIVATE_FLAG;
41
42
43void
44futex_wait (std::atomic<int> *addr, int val)
45{
46 long res;
47
48 res = sys_futex0 (addr, gtm_futex_wait, val);
49 if (__builtin_expect (res == -ENOSYS, 0))
50 {
51 gtm_futex_wait = FUTEX_WAIT;
52 gtm_futex_wake = FUTEX_WAKE;
53 res = sys_futex0 (addr, FUTEX_WAIT, val);
54 }
55 if (__builtin_expect (res < 0, 0))
56 {
57 if (res == -EWOULDBLOCK || res == -ETIMEDOUT)
58 ;
59 else if (res == -EFAULT)
60 GTM_fatal ("futex failed (EFAULT %p)", addr);
61 else
62 GTM_fatal ("futex failed (%s)", strerror(-res));
63 }
64}
65
66
67long
68futex_wake (std::atomic<int> *addr, int count)
69{
70 long res = sys_futex0 (addr, gtm_futex_wake, count);
71 if (__builtin_expect (res == -ENOSYS, 0))
72 {
73 gtm_futex_wait = FUTEX_WAIT;
74 gtm_futex_wake = FUTEX_WAKE;
75 res = sys_futex0 (addr, FUTEX_WAKE, count);
76 }
77 if (__builtin_expect (res < 0, 0))
78 GTM_fatal ("futex failed (%s)", strerror(-res));
79 else
80 return res;
81}
82
83} // namespace GTM
84