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
   7 static 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         PPC_ACQUIRE_BARRIER
  19         "\n\
  20 2:"
  21         : "=&r" (t)
  22         : "r" (&v->counter), "r" (old), "r" (new)
  23         : "cc", "memory");
  24
  25         return t;
  26 }
  27
  28 static 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         PPC_ACQUIRE_BARRIER
  39         : "=&r" (t)
  40         : "r" (&v->counter)
  41         : "cc", "memory");
  42
  43         return t;
  44 }
  45
  46 static inline int __mutex_inc_return_unlock(atomic_t *v)
  47 {
  48         int t;
  49
  50         __asm__ __volatile__(
  51         PPC_RELEASE_BARRIER
  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  */
  74 static 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  */
  91 static 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  */
 108 static 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  */
 126 static 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