/* 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