alistair23-linux/include/asm-x86_64/rwlock.h
Gerd Hoffmann d167a51877 [PATCH] x86_64: x86_64 version of the smp alternative patch.
Changes are largely identical to the i386 version:

 * alternative #define are moved to the new alternative.h file.
 * one new elf section with pointers to the lock prefixes which can be
   nop'ed out for non-smp.
 * two new elf sections simliar to the "classic" alternatives to
   replace SMP code with simpler UP code.
 * fixup headers to use alternative.h instead of defining their own
   LOCK / LOCK_PREFIX macros.

The patch reuses the i386 version of the alternatives code to avoid code
duplication.  The code in alternatives.c was shuffled around a bit to
reduce the number of #ifdefs needed.  It also got some tweaks needed for
x86_64 (vsyscall page handling) and new features (noreplacement option
which was x86_64 only up to now).  Debug printk's are changed from
compile-time to runtime.

Loosely based on a early version from Bastian Blank <waldi@debian.org>

Signed-off-by: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 10:48:14 -07:00

87 lines
2.4 KiB
C

/* include/asm-x86_64/rwlock.h
*
* Helpers used by both rw spinlocks and rw semaphores.
*
* Based in part on code from semaphore.h and
* spinlock.h Copyright 1996 Linus Torvalds.
*
* Copyright 1999 Red Hat, Inc.
* Copyright 2001,2002 SuSE labs
*
* Written by Benjamin LaHaise.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef _ASM_X86_64_RWLOCK_H
#define _ASM_X86_64_RWLOCK_H
#include <linux/stringify.h>
#define RW_LOCK_BIAS 0x01000000
#define RW_LOCK_BIAS_STR "0x01000000"
#define __build_read_lock_ptr(rw, helper) \
asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t" \
"js 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tcall " helper "\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
::"a" (rw) : "memory")
#define __build_read_lock_const(rw, helper) \
asm volatile(LOCK_PREFIX "subl $1,%0\n\t" \
"js 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tpushq %%rax\n\t" \
"leaq %0,%%rax\n\t" \
"call " helper "\n\t" \
"popq %%rax\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
:"=m" (*((volatile int *)rw))::"memory")
#define __build_read_lock(rw, helper) do { \
if (__builtin_constant_p(rw)) \
__build_read_lock_const(rw, helper); \
else \
__build_read_lock_ptr(rw, helper); \
} while (0)
#define __build_write_lock_ptr(rw, helper) \
asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
"jnz 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tcall " helper "\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
::"a" (rw) : "memory")
#define __build_write_lock_const(rw, helper) \
asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
"jnz 2f\n" \
"1:\n" \
LOCK_SECTION_START("") \
"2:\tpushq %%rax\n\t" \
"leaq %0,%%rax\n\t" \
"call " helper "\n\t" \
"popq %%rax\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END \
:"=m" (*((volatile long *)rw))::"memory")
#define __build_write_lock(rw, helper) do { \
if (__builtin_constant_p(rw)) \
__build_write_lock_const(rw, helper); \
else \
__build_write_lock_ptr(rw, helper); \
} while (0)
#endif