1/* sem_wait -- wait on a semaphore. Generic futex-using version.
2 Copyright (C) 2003-2016 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C 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 GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20#include <lowlevellock.h> /* lll_futex* used by the old code. */
21#include "sem_waitcommon.c"
22
23int
24__new_sem_wait (sem_t *sem)
25{
26 if (__new_sem_wait_fast ((struct new_sem *) sem, 0) == 0)
27 return 0;
28 else
29 return __new_sem_wait_slow((struct new_sem *) sem, NULL);
30}
31versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1);
32
33#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
34int
35attribute_compat_text_section
36__old_sem_wait (sem_t *sem)
37{
38 int *futex = (int *) sem;
39 int err;
40
41 do
42 {
43 if (atomic_decrement_if_positive (futex) > 0)
44 return 0;
45
46 /* Enable asynchronous cancellation. Required by the standard. */
47 int oldtype = __pthread_enable_asynccancel ();
48
49 /* Always assume the semaphore is shared. */
50 err = lll_futex_wait (futex, 0, LLL_SHARED);
51
52 /* Disable asynchronous cancellation. */
53 __pthread_disable_asynccancel (oldtype);
54 }
55 while (err == 0 || err == -EWOULDBLOCK);
56
57 __set_errno (-err);
58 return -1;
59}
60
61compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0);
62#endif
63
64int
65__new_sem_trywait (sem_t *sem)
66{
67 /* We must not fail spuriously, so require a definitive result even if this
68 may lead to a long execution time. */
69 if (__new_sem_wait_fast ((struct new_sem *) sem, 1) == 0)
70 return 0;
71 __set_errno (EAGAIN);
72 return -1;
73}
74versioned_symbol (libpthread, __new_sem_trywait, sem_trywait, GLIBC_2_1);
75#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
76int
77__old_sem_trywait (sem_t *sem)
78{
79 int *futex = (int *) sem;
80 int val;
81
82 if (*futex > 0)
83 {
84 val = atomic_decrement_if_positive (futex);
85 if (val > 0)
86 return 0;
87 }
88
89 __set_errno (EAGAIN);
90 return -1;
91}
92compat_symbol (libpthread, __old_sem_trywait, sem_trywait, GLIBC_2_0);
93#endif
94