File: /usr/include/asm/rwlock.h

1     /* include/asm-i386/rwlock.h
2      *
3      *	Helpers used by both rw spinlocks and rw semaphores.
4      *
5      *	Based in part on code from semaphore.h and
6      *	spinlock.h Copyright 1996 Linus Torvalds.
7      *
8      *	Copyright 1999 Red Hat, Inc.
9      *
10      *	Written by Benjamin LaHaise.
11      *
12      *	This program is free software; you can redistribute it and/or
13      *	modify it under the terms of the GNU General Public License
14      *	as published by the Free Software Foundation; either version
15      *	2 of the License, or (at your option) any later version.
16      */
17     #ifndef _ASM_I386_RWLOCK_H
18     #define _ASM_I386_RWLOCK_H
19     
20     #define RW_LOCK_BIAS		 0x01000000
21     #define RW_LOCK_BIAS_STR	"0x01000000"
22     
23     #define __build_read_lock_ptr(rw, helper)   \
24     	asm volatile(LOCK "subl $1,(%0)\n\t" \
25     		     "js 2f\n" \
26     		     "1:\n" \
27     		     ".section .text.lock,\"ax\"\n" \
28     		     "2:\tcall " helper "\n\t" \
29     		     "jmp 1b\n" \
30     		     ".previous" \
31     		     ::"a" (rw) : "memory")
32     
33     #define __build_read_lock_const(rw, helper)   \
34     	asm volatile(LOCK "subl $1,%0\n\t" \
35     		     "js 2f\n" \
36     		     "1:\n" \
37     		     ".section .text.lock,\"ax\"\n" \
38     		     "2:\tpushl %%eax\n\t" \
39     		     "leal %0,%%eax\n\t" \
40     		     "call " helper "\n\t" \
41     		     "popl %%eax\n\t" \
42     		     "jmp 1b\n" \
43     		     ".previous" \
44     		     :"=m" (*(volatile int *)rw) : : "memory")
45     
46     #define __build_read_lock(rw, helper)	do { \
47     						if (__builtin_constant_p(rw)) \
48     							__build_read_lock_const(rw, helper); \
49     						else \
50     							__build_read_lock_ptr(rw, helper); \
51     					} while (0)
52     
53     #define __build_write_lock_ptr(rw, helper) \
54     	asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
55     		     "jnz 2f\n" \
56     		     "1:\n" \
57     		     ".section .text.lock,\"ax\"\n" \
58     		     "2:\tcall " helper "\n\t" \
59     		     "jmp 1b\n" \
60     		     ".previous" \
61     		     ::"a" (rw) : "memory")
62     
63     #define __build_write_lock_const(rw, helper) \
64     	asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
65     		     "jnz 2f\n" \
66     		     "1:\n" \
67     		     ".section .text.lock,\"ax\"\n" \
68     		     "2:\tpushl %%eax\n\t" \
69     		     "leal %0,%%eax\n\t" \
70     		     "call " helper "\n\t" \
71     		     "popl %%eax\n\t" \
72     		     "jmp 1b\n" \
73     		     ".previous" \
74     		     :"=m" (*(volatile int *)rw) : : "memory")
75     
76     #define __build_write_lock(rw, helper)	do { \
77     						if (__builtin_constant_p(rw)) \
78     							__build_write_lock_const(rw, helper); \
79     						else \
80     							__build_write_lock_ptr(rw, helper); \
81     					} while (0)
82     
83     #endif
84