LXR linux-bk/include/asm-mips/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
  64#define spin_trylock(lock) (!test_and_set_bit(0,(lock)))
  65
  66/*
  67 * Read-write spinlocks, allowing multiple readers but only one writer.
  68 *
  69 * NOTE! it is quite common to have readers in interrupts but no interrupt
  70 * writers. For those circumstances we can "mix" irq-safe locks - any writer
  71 * needs to get a irq-safe write-lock, but readers can get non-irqsafe
  72 * read-locks.
  73 */
  74
  75typedef struct {
  76        volatile unsigned int lock;
  77} rwlock_t;
  78
  79#define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
  80
  81static inline void read_lock(rwlock_t *rw)
  82{
  83        unsigned int tmp;
  84
  85        __asm__ __volatile__(
  86        ".set\tnoreorder\t\t\t# read_lock\n"
  87        "1:\tll\t%1, %2\n\t"
  88        "bltz\t%1, 1b\n\t"
  89        " addu\t%1, 1\n\t"
  90        "sc\t%1, %0\n\t"
  91        "beqz\t%1, 1b\n\t"
  92        " sync\n\t"
  93        ".set\treorder" 
  94        : "=o" (rw->lock), "=&r" (tmp)
  95        : "o" (rw->lock)
  96        : "memory");
  97}
  98
  99/* Note the use of sub, not subu which will make the kernel die with an
 100   overflow exception if we ever try to unlock an rwlock that is already
 101   unlocked or is being held by a writer.  */
 102static inline void read_unlock(rwlock_t *rw)
 103{
 104        unsigned int tmp;
 105
 106        __asm__ __volatile__(
 107        ".set\tnoreorder\t\t\t# read_unlock\n"
 108        "1:\tll\t%1, %2\n\t"
 109        "sub\t%1, 1\n\t"
 110        "sc\t%1, %0\n\t"
 111        "beqz\t%1, 1b\n\t"
 112        ".set\treorder" 
 113        : "=o" (rw->lock), "=&r" (tmp)
 114        : "o" (rw->lock)
 115        : "memory");
 116}
 117
 118static inline void write_lock(rwlock_t *rw)
 119{
 120        unsigned int tmp;
 121
 122        __asm__ __volatile__(
 123        ".set\tnoreorder\t\t\t# write_lock\n"
 124        "1:\tll\t%1, %2\n\t"
 125        "bnez\t%1, 1b\n\t"
 126        " lui\t%1, 0x8000\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_unlock(rwlock_t *rw)
 137{
 138        __asm__ __volatile__(
 139        ".set\tnoreorder\t\t\t# write_unlock\n\t"
 140        "sync\n\t"
 141        "sw\t$0, %0\n\t"
 142        ".set\treorder" 
 143        : "=o" (rw->lock)
 144        : "o" (rw->lock)
 145        : "memory");
 146}
 147
 148#endif /* _ASM_SPINLOCK_H */
 149