b862f3b099
Use "+m" rather than a combination of "=m" and "m" for improved clarity and consistency. This also fixes some inlines that incorrectly didn't tell the compiler that they read the old value at all, potentially causing the compiler to generate bogus code. It appear that all of those potential bugs were hidden by the use of extra "volatile" specifiers on the data structures in question, though. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
76 lines
2.0 KiB
C
76 lines
2.0 KiB
C
/* include/asm-i386/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.
|
|
*
|
|
* 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_I386_RWLOCK_H
|
|
#define _ASM_I386_RWLOCK_H
|
|
|
|
#define RW_LOCK_BIAS 0x01000000
|
|
#define RW_LOCK_BIAS_STR "0x01000000"
|
|
|
|
#define __build_read_lock_ptr(rw, helper) \
|
|
alternative_smp("lock; subl $1,(%0)\n\t" \
|
|
"jns 1f\n" \
|
|
"call " helper "\n\t" \
|
|
"1:\n", \
|
|
"subl $1,(%0)\n\t", \
|
|
:"a" (rw) : "memory")
|
|
|
|
#define __build_read_lock_const(rw, helper) \
|
|
alternative_smp("lock; subl $1,%0\n\t" \
|
|
"jns 1f\n" \
|
|
"pushl %%eax\n\t" \
|
|
"leal %0,%%eax\n\t" \
|
|
"call " helper "\n\t" \
|
|
"popl %%eax\n\t" \
|
|
"1:\n", \
|
|
"subl $1,%0\n\t", \
|
|
"+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) \
|
|
alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
|
|
"jz 1f\n" \
|
|
"call " helper "\n\t" \
|
|
"1:\n", \
|
|
"subl $" RW_LOCK_BIAS_STR ",(%0)\n\t", \
|
|
:"a" (rw) : "memory")
|
|
|
|
#define __build_write_lock_const(rw, helper) \
|
|
alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
|
|
"jz 1f\n" \
|
|
"pushl %%eax\n\t" \
|
|
"leal %0,%%eax\n\t" \
|
|
"call " helper "\n\t" \
|
|
"popl %%eax\n\t" \
|
|
"1:\n", \
|
|
"subl $" RW_LOCK_BIAS_STR ",%0\n\t", \
|
|
"+m" (*(volatile int *)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
|