e5c34a57c8
Based on __build_read_lock_const, this looked like a bug. [ Indeed. Maybe nobody uses this version? Worth fixing up anyway ] Signed-off-by: Linus Torvalds <torvalds@osdl.org>
86 lines
2.4 KiB
C
86 lines
2.4 KiB
C
/* include/asm-x86_64/rwlock.h
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*
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* Helpers used by both rw spinlocks and rw semaphores.
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*
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* Based in part on code from semaphore.h and
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* spinlock.h Copyright 1996 Linus Torvalds.
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*
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* Copyright 1999 Red Hat, Inc.
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* Copyright 2001,2002 SuSE labs
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*
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* Written by Benjamin LaHaise.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#ifndef _ASM_X86_64_RWLOCK_H
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#define _ASM_X86_64_RWLOCK_H
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#include <linux/stringify.h>
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#define RW_LOCK_BIAS 0x01000000
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#define RW_LOCK_BIAS_STR "0x01000000"
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#define __build_read_lock_ptr(rw, helper) \
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asm volatile(LOCK "subl $1,(%0)\n\t" \
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"js 2f\n" \
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"1:\n" \
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LOCK_SECTION_START("") \
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"2:\tcall " helper "\n\t" \
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"jmp 1b\n" \
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LOCK_SECTION_END \
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::"a" (rw) : "memory")
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#define __build_read_lock_const(rw, helper) \
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asm volatile(LOCK "subl $1,%0\n\t" \
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"js 2f\n" \
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"1:\n" \
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LOCK_SECTION_START("") \
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"2:\tpushq %%rax\n\t" \
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"leaq %0,%%rax\n\t" \
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"call " helper "\n\t" \
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"popq %%rax\n\t" \
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"jmp 1b\n" \
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LOCK_SECTION_END \
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:"=m" (*((volatile int *)rw))::"memory")
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#define __build_read_lock(rw, helper) do { \
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if (__builtin_constant_p(rw)) \
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__build_read_lock_const(rw, helper); \
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else \
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__build_read_lock_ptr(rw, helper); \
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} while (0)
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#define __build_write_lock_ptr(rw, helper) \
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asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
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"jnz 2f\n" \
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"1:\n" \
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LOCK_SECTION_START("") \
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"2:\tcall " helper "\n\t" \
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"jmp 1b\n" \
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LOCK_SECTION_END \
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::"a" (rw) : "memory")
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#define __build_write_lock_const(rw, helper) \
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asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
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"jnz 2f\n" \
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"1:\n" \
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LOCK_SECTION_START("") \
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"2:\tpushq %%rax\n\t" \
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"leaq %0,%%rax\n\t" \
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"call " helper "\n\t" \
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"popq %%rax\n\t" \
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"jmp 1b\n" \
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LOCK_SECTION_END \
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:"=m" (*((volatile long *)rw))::"memory")
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#define __build_write_lock(rw, helper) do { \
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if (__builtin_constant_p(rw)) \
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__build_write_lock_const(rw, helper); \
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else \
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__build_write_lock_ptr(rw, helper); \
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} while (0)
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#endif
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