lib/ringbuffer/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 #include <asm/atomic.h>
  13 #include <asm/local.h>
  14
  15 /*
  16  * Same data type (long) accessed differently depending on configuration.
  17  * v field is for non-atomic access (protected by mutual exclusion).
  18  * In the fast-path, the ring_buffer_config structure is constant, so the
  19  * compiler can statically select the appropriate branch.
  20  * local_t is used for per-cpu and per-thread buffers.
  21  * atomic_long_t is used for globally shared buffers.
  22  */
  23 union v_atomic {
  24         local_t l;
  25         atomic_long_t a;
  26         long v;
  27 };
  28
  29 static inline
  30 long v_read(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  31 {
  32         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  33                 return local_read(&v_a->l);
  34         else
  35                 return atomic_long_read(&v_a->a);
  36 }
  37
  38 static inline
  39 void v_set(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  40            long v)
  41 {
  42         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  43                 local_set(&v_a->l, v);
  44         else
  45                 atomic_long_set(&v_a->a, v);
  46 }
  47
  48 static inline
  49 void v_add(const struct lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  50 {
  51         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  52                 local_add(v, &v_a->l);
  53         else
  54                 atomic_long_add(v, &v_a->a);
  55 }
  56
  57 static inline
  58 void v_inc(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  59 {
  60         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  61                 local_inc(&v_a->l);
  62         else
  63                 atomic_long_inc(&v_a->a);
  64 }
  65
  66 /*
  67  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  68  */
  69 static inline
  70 void _v_dec(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  71 {
  72         --v_a->v;
  73 }
  74
  75 static inline
  76 long v_cmpxchg(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  77                long old, long _new)
  78 {
  79         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  80                 return local_cmpxchg(&v_a->l, old, _new);
  81         else
  82                 return atomic_long_cmpxchg(&v_a->a, old, _new);
  83 }
  84
  85 #endif /* _LINUX_RING_BUFFER_VATOMIC_H */