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Diffstat (limited to 'include/asm-x86_64/rwlock.h')
| -rw-r--r-- | include/asm-x86_64/rwlock.h | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/include/asm-x86_64/rwlock.h b/include/asm-x86_64/rwlock.h new file mode 100644 index 00000000000..8a78a4ace53 --- /dev/null +++ b/include/asm-x86_64/rwlock.h @@ -0,0 +1,86 @@ +/* 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 |