libringbuffer/vatomic.h

   1 #ifndef _LINUX_RING_BUFFER_VATOMIC_H
   2 #define _LINUX_RING_BUFFER_VATOMIC_H
   3
   4 /*
   5  * linux/ringbuffer/vatomic.h
   6  *
   7  * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Dual LGPL v2.1/GPL v2 license.
  10  */
  11
  12 /*
  13  * Same data type (long) accessed differently depending on configuration.
  14  * v field is for non-atomic access (protected by mutual exclusion).
  15  * In the fast-path, the ring_buffer_config structure is constant, so the
  16  * compiler can statically select the appropriate branch.
  17  * local_t is used for per-cpu and per-thread buffers.
  18  * atomic_long_t is used for globally shared buffers.
  19  */
  20 union v_atomic {
  21         local_t l;
  22         atomic_long_t a;
  23         long v;
  24 };
  25
  26 static inline
  27 long v_read(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  28 {
  29         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  30                 return local_read(&v_a->l);
  31         else
  32                 return atomic_long_read(&v_a->a);
  33 }
  34
  35 static inline
  36 void v_set(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  37            long v)
  38 {
  39         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  40                 local_set(&v_a->l, v);
  41         else
  42                 atomic_long_set(&v_a->a, v);
  43 }
  44
  45 static inline
  46 void v_add(const struct lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  47 {
  48         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  49                 local_add(v, &v_a->l);
  50         else
  51                 atomic_long_add(v, &v_a->a);
  52 }
  53
  54 static inline
  55 void v_inc(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  56 {
  57         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  58                 local_inc(&v_a->l);
  59         else
  60                 atomic_long_inc(&v_a->a);
  61 }
  62
  63 /*
  64  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  65  */
  66 static inline
  67 void _v_dec(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  68 {
  69         --v_a->v;
  70 }
  71
  72 static inline
  73 long v_cmpxchg(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  74                long old, long _new)
  75 {
  76         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  77                 return local_cmpxchg(&v_a->l, old, _new);
  78         else
  79                 return atomic_long_cmpxchg(&v_a->a, old, _new);
  80 }
  81
  82 #endif /* _LINUX_RING_BUFFER_VATOMIC_H */