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
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
/* Machine-dependent pthreads configuration and inline functions.
i386 version.
Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson <rth@tamu.edu>.
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; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#ifndef _PT_MACHINE_H
#define _PT_MACHINE_H 1
#include <features.h>
#ifndef __ASSEMBLER__
#ifndef PT_EI
# define PT_EI __extern_always_inline
#endif
/*
extern long int testandset (int *spinlock);
extern int __compare_and_swap (long int *p, long int oldval, long int newval);
*/
/* Get some notion of the current stack. Need not be exactly the top
of the stack, just something somewhere in the current frame. */
#define CURRENT_STACK_FRAME __builtin_frame_address (0)
/* See if we can optimize for newer cpus... */
#if defined __GNUC__ && __GNUC__ >= 2 && \
(defined __i486__ || defined __pentium__ || defined __pentiumpro__ || defined __pentium4__ || \
defined __athlon__ || defined __k8__)
/* Spinlock implementation; required. */
PT_EI long int
testandset (int *spinlock)
{
long int ret;
__asm__ __volatile__ (
"xchgl %0, %1"
: "=r" (ret), "=m" (*spinlock)
: "0" (1), "m" (*spinlock)
: "memory");
return ret;
}
/* Compare-and-swap for semaphores. It's always available on i686. */
#define HAS_COMPARE_AND_SWAP
PT_EI int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
char ret;
long int readval;
__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
: "=q" (ret), "=m" (*p), "=a" (readval)
: "r" (newval), "m" (*p), "a" (oldval)
: "memory");
return ret;
}
#if __ASSUME_LDT_WORKS > 0
#include "../useldt.h"
#endif
/* The P4 and above really want some help to prevent overheating. */
#define BUSY_WAIT_NOP __asm__ ("rep; nop")
#else /* Generic i386 implementation */
/* Spinlock implementation; required. */
PT_EI long int
testandset (int *spinlock)
{
long int ret;
__asm__ __volatile__(
"xchgl %0, %1"
: "=r"(ret), "=m"(*spinlock)
: "0"(1), "m"(*spinlock)
: "memory");
return ret;
}
/* Compare-and-swap for semaphores.
Available on the 486 and above, but not on the 386.
We test dynamically whether it's available or not. */
#define HAS_COMPARE_AND_SWAP
#define TEST_FOR_COMPARE_AND_SWAP
PT_EI int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
char ret;
long int readval;
__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
: "=q" (ret), "=m" (*p), "=a" (readval)
: "r" (newval), "m" (*p), "a" (oldval)
: "memory");
return ret;
}
PT_EI int
get_eflags (void)
{
int res;
__asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
return res;
}
PT_EI void
set_eflags (int newflags)
{
__asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
}
PT_EI int
compare_and_swap_is_available (void)
{
int oldflags = get_eflags ();
int changed;
/* Flip AC bit in EFLAGS. */
set_eflags (oldflags ^ 0x40000);
/* See if bit changed. */
changed = (get_eflags () ^ oldflags) & 0x40000;
/* Restore EFLAGS. */
set_eflags (oldflags);
/* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
Otherwise, it's a 486 or above and it has cmpxchg. */
return changed != 0;
}
#endif /* Generic i386 implementation */
#endif /* __ASSEMBLER__ */
#endif /* pt-machine.h */
|
