LXR linux/arch/powerpc/include/asm/mutex.h

   1/*
   2 * Optimised mutex implementation of include/asm-generic/mutex-dec.h algorithm
   3 */
   4#ifndef _ASM_POWERPC_MUTEX_H
   5#define _ASM_POWERPC_MUTEX_H
   6
   7static inline int __mutex_cmpxchg_lock(atomic_t *v, int old, int new)
   8{
   9        int t;
  10
  11        __asm__ __volatile__ (
  12"1:     lwarx   %0,0,%1         # mutex trylock\n\
  13        cmpw    0,%0,%2\n\
  14        bne-    2f\n"
  15        PPC405_ERR77(0,%1)
  16"       stwcx.  %3,0,%1\n\
  17        bne-    1b"
  18        ISYNC_ON_SMP
  19        "\n\
  202:"
  21        : "=&r" (t)
  22        : "r" (&v->counter), "r" (old), "r" (new)
  23        : "cc", "memory");
  24
  25        return t;
  26}
  27
  28static inline int __mutex_dec_return_lock(atomic_t *v)
  29{
  30        int t;
  31
  32        __asm__ __volatile__(
  33"1:     lwarx   %0,0,%1         # mutex lock\n\
  34        addic   %0,%0,-1\n"
  35        PPC405_ERR77(0,%1)
  36"       stwcx.  %0,0,%1\n\
  37        bne-    1b"
  38        ISYNC_ON_SMP
  39        : "=&r" (t)
  40        : "r" (&v->counter)
  41        : "cc", "memory");
  42
  43        return t;
  44}
  45
  46static inline int __mutex_inc_return_unlock(atomic_t *v)
  47{
  48        int t;
  49
  50        __asm__ __volatile__(
  51        LWSYNC_ON_SMP
  52"1:     lwarx   %0,0,%1         # mutex unlock\n\
  53        addic   %0,%0,1\n"
  54        PPC405_ERR77(0,%1)
  55"       stwcx.  %0,0,%1 \n\
  56        bne-    1b"
  57        : "=&r" (t)
  58        : "r" (&v->counter)
  59        : "cc", "memory");
  60
  61        return t;
  62}
  63
  64/**
  65 *  __mutex_fastpath_lock - try to take the lock by moving the count
  66 *                          from 1 to a 0 value
  67 *  @count: pointer of type atomic_t
  68 *  @fail_fn: function to call if the original value was not 1
  69 *
  70 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
  71 * it wasn't 1 originally. This function MUST leave the value lower than
  72 * 1 even when the "1" assertion wasn't true.
  73 */
  74static inline void
  75__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
  76{
  77        if (unlikely(__mutex_dec_return_lock(count) < 0))
  78                fail_fn(count);
  79}
  80
  81/**
  82 *  __mutex_fastpath_lock_retval - try to take the lock by moving the count
  83 *                                 from 1 to a 0 value
  84 *  @count: pointer of type atomic_t
  85 *  @fail_fn: function to call if the original value was not 1
  86 *
  87 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
  88 * it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
  89 * or anything the slow path function returns.
  90 */
  91static inline int
  92__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
  93{
  94        if (unlikely(__mutex_dec_return_lock(count) < 0))
  95                return fail_fn(count);
  96        return 0;
  97}
  98
  99/**
 100 *  __mutex_fastpath_unlock - try to promote the count from 0 to 1
 101 *  @count: pointer of type atomic_t
 102 *  @fail_fn: function to call if the original value was not 0
 103 *
 104 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
 105 * In the failure case, this function is allowed to either set the value to
 106 * 1, or to set it to a value lower than 1.
 107 */
 108static inline void
 109__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 110{
 111        if (unlikely(__mutex_inc_return_unlock(count) <= 0))
 112                fail_fn(count);
 113}
 114
 115#define __mutex_slowpath_needs_to_unlock()              1
 116
 117/**
 118 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
 119 *
 120 *  @count: pointer of type atomic_t
 121 *  @fail_fn: fallback function
 122 *
 123 * Change the count from 1 to 0, and return 1 (success), or if the count
 124 * was not 1, then return 0 (failure).
 125 */
 126static inline int
 127__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 128{
 129        if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
 130                return 1;
 131        return 0;
 132}
 133
 134#endif
 135