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