LXR linux-bk/include/asm-mips64/spinlock.h

   1/*
   2 * This file is subject to the terms and conditions of the GNU General Public
   3 * License.  See the file "COPYING" in the main directory of this archive
   4 * for more details.
   5 *
   6 * Copyright (C) 1999, 2000 by Ralf Baechle
   7 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
   8 */
   9#ifndef _ASM_SPINLOCK_H
  10#define _ASM_SPINLOCK_H
  11
  12/*
  13 * Your basic SMP spinlocks, allowing only a single CPU anywhere
  14 */
  15
  16typedef struct {
  17        volatile unsigned int lock;
  18} spinlock_t;
  19
  20#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
  21
  22#define spin_lock_init(x)       do { (x)->lock = 0; } while(0)
  23
  24#define spin_is_locked(x)       ((x)->lock != 0)
  25#define spin_unlock_wait(x)     do { barrier(); } while ((x)->lock)
  26
  27/*
  28 * Simple spin lock operations.  There are two variants, one clears IRQ's
  29 * on the local processor, one does not.
  30 *
  31 * We make no fairness assumptions.  They have a cost.
  32 */
  33
  34static inline void spin_lock(spinlock_t *lock)
  35{
  36        unsigned int tmp;
  37
  38        __asm__ __volatile__(
  39        ".set\tnoreorder\t\t\t# spin_lock\n"
  40        "1:\tll\t%1, %2\n\t"
  41        "bnez\t%1, 1b\n\t"
  42        " li\t%1, 1\n\t"
  43        "sc\t%1, %0\n\t"
  44        "beqz\t%1, 1b\n\t"
  45        " sync\n\t"
  46        ".set\treorder"
  47        : "=o" (lock->lock), "=&r" (tmp)
  48        : "o" (lock->lock)
  49        : "memory");
  50}
  51
  52static inline void spin_unlock(spinlock_t *lock)
  53{
  54        __asm__ __volatile__(
  55        ".set\tnoreorder\t\t\t# spin_unlock\n\t"
  56        "sync\n\t"
  57        "sw\t$0, %0\n\t"
  58        ".set\treorder" 
  59        : "=o" (lock->lock)
  60        : "o" (lock->lock)
  61        : "memory");
  62}
  63
  64static inline unsigned int spin_trylock(spinlock_t *lock)
  65{
  66        unsigned int temp, res;
  67
  68        __asm__ __volatile__(
  69        ".set\tnoreorder\t\t\t# spin_trylock\n\t"
  70        "1:\tll\t%0, %1\n\t"
  71        "or\t%2, %0, %3\n\t"
  72        "sc\t%2, %1\n\t"
  73        "beqz\t%2, 1b\n\t"
  74        " and\t%2, %0, %3\n\t"
  75        ".set\treorder"
  76        : "=&r" (temp), "=m" (lock->lock), "=&r" (res)
  77        : "r" (1), "m" (lock->lock)
  78        : "memory");
  79
  80        return res == 0;
  81}
  82
  83/*
  84 * Read-write spinlocks, allowing multiple readers but only one writer.
  85 *
  86 * NOTE! it is quite common to have readers in interrupts but no interrupt
  87 * writers. For those circumstances we can "mix" irq-safe locks - any writer
  88 * needs to get a irq-safe write-lock, but readers can get non-irqsafe
  89 * read-locks.
  90 */
  91
  92typedef struct {
  93        volatile unsigned int lock;
  94} rwlock_t;
  95
  96#define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
  97
  98static inline void read_lock(rwlock_t *rw)
  99{
 100        unsigned int tmp;
 101
 102        __asm__ __volatile__(
 103        ".set\tnoreorder\t\t\t# read_lock\n"
 104        "1:\tll\t%1, %2\n\t"
 105        "bltz\t%1, 1b\n\t"
 106        " addu\t%1, 1\n\t"
 107        "sc\t%1, %0\n\t"
 108        "beqz\t%1, 1b\n\t"
 109        " sync\n\t"
 110        ".set\treorder" 
 111        : "=o" (rw->lock), "=&r" (tmp)
 112        : "o" (rw->lock)
 113        : "memory");
 114}
 115
 116/* Note the use of sub, not subu which will make the kernel die with an
 117   overflow exception if we ever try to unlock an rwlock that is already
 118   unlocked or is being held by a writer.  */
 119static inline void read_unlock(rwlock_t *rw)
 120{
 121        unsigned int tmp;
 122
 123        __asm__ __volatile__(
 124        ".set\tnoreorder\t\t\t# read_unlock\n"
 125        "1:\tll\t%1, %2\n\t"
 126        "sub\t%1, 1\n\t"
 127        "sc\t%1, %0\n\t"
 128        "beqz\t%1, 1b\n\t"
 129        "sync\n\t"
 130        ".set\treorder" 
 131        : "=o" (rw->lock), "=&r" (tmp)
 132        : "o" (rw->lock)
 133        : "memory");
 134}
 135
 136static inline void write_lock(rwlock_t *rw)
 137{
 138        unsigned int tmp;
 139
 140        __asm__ __volatile__(
 141        ".set\tnoreorder\t\t\t# write_lock\n"
 142        "1:\tll\t%1, %2\n\t"
 143        "bnez\t%1, 1b\n\t"
 144        " lui\t%1, 0x8000\n\t"
 145        "sc\t%1, %0\n\t"
 146        "beqz\t%1, 1b\n\t"
 147        " sync\n\t"
 148        ".set\treorder" 
 149        : "=o" (rw->lock), "=&r" (tmp)
 150        : "o" (rw->lock)
 151        : "memory");
 152}
 153
 154static inline void write_unlock(rwlock_t *rw)
 155{
 156        __asm__ __volatile__(
 157        ".set\tnoreorder\t\t\t# write_unlock\n\t"
 158        "sync\n\t"
 159        "sw\t$0, %0\n\t"
 160        ".set\treorder" 
 161        : "=o" (rw->lock)
 162        : "o" (rw->lock)
 163        : "memory");
 164}
 165
 166#endif /* _ASM_SPINLOCK_H */
 167