| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* include/asm-i386/rwlock.h |
| 2 | * |
| 3 | * Helpers used by both rw spinlocks and rw semaphores. |
| 4 | * |
| 5 | * Based in part on code from semaphore.h and |
| 6 | * spinlock.h Copyright 1996 Linus Torvalds. |
| 7 | * |
| 8 | * Copyright 1999 Red Hat, Inc. |
| 9 | * |
| 10 | * Written by Benjamin LaHaise. |
| 11 | * |
| 12 | * This program is free software; you can redistribute it and/or |
| 13 | * modify it under the terms of the GNU General Public License |
| 14 | * as published by the Free Software Foundation; either version |
| 15 | * 2 of the License, or (at your option) any later version. |
| 16 | */ |
| 17 | #ifndef _ASM_I386_RWLOCK_H |
| 18 | #define _ASM_I386_RWLOCK_H |
| 19 | |
| 20 | #define RW_LOCK_BIAS 0x01000000 |
| 21 | #define RW_LOCK_BIAS_STR "0x01000000" |
| 22 | |
| 23 | #define __build_read_lock_ptr(rw, helper) \ |
| 24 | asm volatile(LOCK "subl $1,(%0)\n\t" \ |
| 25 | "jns 1f\n" \ |
| 26 | "call " helper "\n\t" \ |
| 27 | "1:\n" \ |
| 28 | ::"a" (rw) : "memory") |
| 29 | |
| 30 | #define __build_read_lock_const(rw, helper) \ |
| 31 | asm volatile(LOCK "subl $1,%0\n\t" \ |
| 32 | "jns 1f\n" \ |
| 33 | "pushl %%eax\n\t" \ |
| 34 | "leal %0,%%eax\n\t" \ |
| 35 | "call " helper "\n\t" \ |
| 36 | "popl %%eax\n\t" \ |
| 37 | "1:\n" \ |
| 38 | :"=m" (*(volatile int *)rw) : : "memory") |
| 39 | |
| 40 | #define __build_read_lock(rw, helper) do { \ |
| 41 | if (__builtin_constant_p(rw)) \ |
| 42 | __build_read_lock_const(rw, helper); \ |
| 43 | else \ |
| 44 | __build_read_lock_ptr(rw, helper); \ |
| 45 | } while (0) |
| 46 | |
| 47 | #define __build_write_lock_ptr(rw, helper) \ |
| 48 | asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \ |
| 49 | "jz 1f\n" \ |
| 50 | "call " helper "\n\t" \ |
| 51 | "1:\n" \ |
| 52 | ::"a" (rw) : "memory") |
| 53 | |
| 54 | #define __build_write_lock_const(rw, helper) \ |
| 55 | asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \ |
| 56 | "jz 1f\n" \ |
| 57 | "pushl %%eax\n\t" \ |
| 58 | "leal %0,%%eax\n\t" \ |
| 59 | "call " helper "\n\t" \ |
| 60 | "popl %%eax\n\t" \ |
| 61 | "1:\n" \ |
| 62 | :"=m" (*(volatile int *)rw) : : "memory") |
| 63 | |
| 64 | #define __build_write_lock(rw, helper) do { \ |
| 65 | if (__builtin_constant_p(rw)) \ |
| 66 | __build_write_lock_const(rw, helper); \ |
| 67 | else \ |
| 68 | __build_write_lock_ptr(rw, helper); \ |
| 69 | } while (0) |
| 70 | |
| 71 | #endif |