1 /* Machine-dependent pthreads configuration and inline functions.
2 i386 version.
3 Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5 Contributed by Richard Henderson <rth@tamu.edu>.
6
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public License as
9 published by the Free Software Foundation; either version 2.1 of the
10 License, or (at your option) any later version.
11
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
16
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; see the file COPYING.LIB. If not,
19 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
21
22 #if defined __pentiumpro__ || defined __pentium4__ || defined __athlon__ || \
23 defined __k8__
24 # include "i686/pt-machine.h"
25 #else
26
27 #ifndef _PT_MACHINE_H
28 #define _PT_MACHINE_H 1
29
30 #ifndef __ASSEMBLER__
31 #ifndef PT_EI
32 # define PT_EI __extern_always_inline
33 #endif
34
35 #ifdef not_for_l4
36 extern long int testandset (int *spinlock);
37 extern int __compare_and_swap (long int *p, long int oldval, long int newval);
38 #endif
39 /* Get some notion of the current stack. Need not be exactly the top
40 of the stack, just something somewhere in the current frame. */
41 #define CURRENT_STACK_FRAME __builtin_frame_address (0)
42
43
44 /* Spinlock implementation; required. */
45 PT_EI long int
testandset(int * spinlock)46 testandset (int *spinlock)
47 {
48 long int ret;
49
50 __asm__ __volatile__(
51 "xchgl %0, %1"
52 : "=r"(ret), "=m"(*spinlock)
53 : "0"(1), "m"(*spinlock)
54 : "memory");
55
56 return ret;
57 }
58
59
60 /* Compare-and-swap for semaphores.
61 Available on the 486 and above, but not on the 386.
62 We test dynamically whether it's available or not. */
63
64 #define HAS_COMPARE_AND_SWAP
65 #define TEST_FOR_COMPARE_AND_SWAP
66
67 PT_EI int
__compare_and_swap(long int * p,long int oldval,long int newval)68 __compare_and_swap (long int *p, long int oldval, long int newval)
69 {
70 char ret;
71 long int readval;
72
73 __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
74 : "=q" (ret), "=m" (*p), "=a" (readval)
75 : "r" (newval), "m" (*p), "a" (oldval)
76 : "memory");
77 return ret;
78 }
79
80
81 PT_EI int get_eflags (void);
82 PT_EI int
get_eflags(void)83 get_eflags (void)
84 {
85 int res;
86 __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
87 return res;
88 }
89
90
91 PT_EI void set_eflags (int newflags);
92 PT_EI void
set_eflags(int newflags)93 set_eflags (int newflags)
94 {
95 __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
96 }
97
98
99 PT_EI int compare_and_swap_is_available (void);
100 PT_EI int
compare_and_swap_is_available(void)101 compare_and_swap_is_available (void)
102 {
103 int oldflags = get_eflags ();
104 int changed;
105 /* Flip AC bit in EFLAGS. */
106 set_eflags (oldflags ^ 0x40000);
107 /* See if bit changed. */
108 changed = (get_eflags () ^ oldflags) & 0x40000;
109 /* Restore EFLAGS. */
110 set_eflags (oldflags);
111 /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
112 Otherwise, it's a 486 or above and it has cmpxchg. */
113 return changed != 0;
114 }
115 #endif /* __ASSEMBLER__ */
116
117 #endif /* pt-machine.h */
118
119 #endif
120