arch/blackfin/include/asm/mutex.h

   1 /*
   2  * Pull in the generic implementation for the mutex fastpath.
   3  *
   4  * TODO: implement optimized primitives instead, or leave the generic
   5  * implementation in place, or pick the atomic_xchg() based generic
   6  * implementation. (see asm-generic/mutex-xchg.h for details)
   7  *
   8  * Copyright 2006-2009 Analog Devices Inc.
   9  *
  10  * Licensed under the GPL-2 or later.
  11  */
  12
  13 #ifndef _ASM_MUTEX_H
  14 #define _ASM_MUTEX_H
  15
  16 #ifndef CONFIG_SMP
  17 #include <asm-generic/mutex.h>
  18 #else
  19
  20 static inline void
  21 __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
  22 {
  23         if (unlikely(atomic_dec_return(count) < 0))
  24                 fail_fn(count);
  25         else
  26                 smp_mb();
  27 }
  28
  29 static inline int
  30 __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
  31 {
  32         if (unlikely(atomic_dec_return(count) < 0))
  33                 return fail_fn(count);
  34         else {
  35                 smp_mb();
  36                 return 0;
  37         }
  38 }
  39
  40 static inline void
  41 __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
  42 {
  43         smp_mb();
  44         if (unlikely(atomic_inc_return(count) <= 0))
  45                 fail_fn(count);
  46 }
  47
  48 #define __mutex_slowpath_needs_to_unlock()              1
  49
  50 static inline int
  51 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
  52 {
  53         /*
  54          * We have two variants here. The cmpxchg based one is the best one
  55          * because it never induce a false contention state.  It is included
  56          * here because architectures using the inc/dec algorithms over the
  57          * xchg ones are much more likely to support cmpxchg natively.
  58          *
  59          * If not we fall back to the spinlock based variant - that is
  60          * just as efficient (and simpler) as a 'destructive' probing of
  61          * the mutex state would be.
  62          */
  63 #ifdef __HAVE_ARCH_CMPXCHG
  64         if (likely(atomic_cmpxchg(count, 1, 0) == 1)) {
  65                 smp_mb();
  66                 return 1;
  67         }
  68         return 0;
  69 #else
  70         return fail_fn(count);
  71 #endif
  72 }
  73
  74 #endif
  75
  76 #endif