1/* include/asm-x86_64/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 *	Copyright 2001,2002 SuSE labs
10 *
11 *	Written by Benjamin LaHaise.
12 *
13 *	This program is free software; you can redistribute it and/or
14 *	modify it under the terms of the GNU General Public License
15 *	as published by the Free Software Foundation; either version
16 *	2 of the License, or (at your option) any later version.
17 */
18#ifndef _ASM_X86_64_RWLOCK_H
19#define _ASM_X86_64_RWLOCK_H
20
21#include <linux/stringify.h>
22
23#define RW_LOCK_BIAS		 0x01000000
24#define RW_LOCK_BIAS_STR	"0x01000000"
25
26#define __build_read_lock_ptr(rw, helper)   \
27	asm volatile(LOCK "subl $1,(%0)\n\t" \
28		     "js 2f\n" \
29		     "1:\n" \
30		    LOCK_SECTION_START("") \
31		     "2:\tcall " helper "\n\t" \
32		     "jmp 1b\n" \
33		    LOCK_SECTION_END \
34		     ::"a" (rw) : "memory")
35
36#define __build_read_lock_const(rw, helper)   \
37	asm volatile(LOCK "subl $1,%0\n\t" \
38		     "js 2f\n" \
39		     "1:\n" \
40		    LOCK_SECTION_START("") \
41		     "2:\tpushq %%rax\n\t" \
42		     "leaq %0,%%rax\n\t" \
43		     "call " helper "\n\t" \
44		     "popq %%rax\n\t" \
45		     "jmp 1b\n" \
46		    LOCK_SECTION_END \
47		     :"=m" (*((volatile int *)rw))::"memory")
48
49#define __build_read_lock(rw, helper)	do { \
50						if (__builtin_constant_p(rw)) \
51							__build_read_lock_const(rw, helper); \
52						else \
53							__build_read_lock_ptr(rw, helper); \
54					} while (0)
55
56#define __build_write_lock_ptr(rw, helper) \
57	asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
58		     "jnz 2f\n" \
59		     "1:\n" \
60		     LOCK_SECTION_START("") \
61		     "2:\tcall " helper "\n\t" \
62		     "jmp 1b\n" \
63		     LOCK_SECTION_END \
64		     ::"a" (rw) : "memory")
65
66#define __build_write_lock_const(rw, helper) \
67	asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
68		     "jnz 2f\n" \
69		     "1:\n" \
70		    LOCK_SECTION_START("") \
71		     "2:\tpushq %%rax\n\t" \
72		     "leaq %0,%%rax\n\t" \
73		     "call " helper "\n\t" \
74		     "popq %%rax\n\t" \
75		     "jmp 1b\n" \
76		    LOCK_SECTION_END \
77		     :"=m" (*((volatile long *)rw))::"memory")
78
79#define __build_write_lock(rw, helper)	do { \
80						if (__builtin_constant_p(rw)) \
81							__build_write_lock_const(rw, helper); \
82						else \
83							__build_write_lock_ptr(rw, helper); \
84					} while (0)
85
86#endif
87