1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
/* sem_wait -- wait on a semaphore. Generic futex-using version.
Copyright (C) 2003-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <internaltypes.h>
#include <semaphore.h>
#include <pthreadP.h>
#include <shlib-compat.h>
#include <atomic.h>
void
attribute_hidden
__sem_wait_cleanup (void *arg)
{
struct new_sem *isem = (struct new_sem *) arg;
atomic_decrement (&isem->nwaiters);
}
/* This is in a seperate function in order to make sure gcc
puts the call site into an exception region, and thus the
cleanups get properly run. */
static int
__attribute__ ((noinline))
do_futex_wait (struct new_sem *isem)
{
int err, oldtype = __pthread_enable_asynccancel ();
err = lll_futex_wait (&isem->value, 0, isem->private ^ FUTEX_PRIVATE_FLAG);
__pthread_disable_asynccancel (oldtype);
return err;
}
int
__new_sem_wait (sem_t *sem)
{
struct new_sem *isem = (struct new_sem *) sem;
int err;
if (atomic_decrement_if_positive (&isem->value) > 0)
return 0;
atomic_increment (&isem->nwaiters);
pthread_cleanup_push (__sem_wait_cleanup, isem);
while (1)
{
err = do_futex_wait(isem);
if (err != 0 && err != -EWOULDBLOCK)
{
__set_errno (-err);
err = -1;
break;
}
if (atomic_decrement_if_positive (&isem->value) > 0)
{
err = 0;
break;
}
}
pthread_cleanup_pop (0);
atomic_decrement (&isem->nwaiters);
return err;
}
versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1);
#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
int
attribute_compat_text_section
__old_sem_wait (sem_t *sem)
{
int *futex = (int *) sem;
int err;
do
{
if (atomic_decrement_if_positive (futex) > 0)
return 0;
/* Enable asynchronous cancellation. Required by the standard. */
int oldtype = __pthread_enable_asynccancel ();
/* Always assume the semaphore is shared. */
err = lll_futex_wait (futex, 0, LLL_SHARED);
/* Disable asynchronous cancellation. */
__pthread_disable_asynccancel (oldtype);
}
while (err == 0 || err == -EWOULDBLOCK);
__set_errno (-err);
return -1;
}
compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0);
#endif
|
