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/* 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 "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 "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 "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 "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