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  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
  10  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
  11  *
  12  * Permission is hereby granted to use or copy this program
  13  * for any purpose,  provided the above notices are retained on all copies.
  14  * Permission to modify the code and to distribute modified code is granted,
  15  * provided the above notices are retained, and a notice that the code was
  16  * modified is included with the above copyright notice.
  17  */
  18
  19 #include <assert.h>
  20 #include <urcu/uatomic.h>
  21
  22 /*
  23  * Same data type (long) accessed differently depending on configuration.
  24  * v field is for non-atomic access (protected by mutual exclusion).
  25  * In the fast-path, the ring_buffer_config structure is constant, so the
  26  * compiler can statically select the appropriate branch.
  27  * local_t is used for per-cpu and per-thread buffers.
  28  * atomic_long_t is used for globally shared buffers.
  29  */
  30 union v_atomic {
  31         long a; /* accessed through uatomic */
  32         long v;
  33 };
  34
  35 static inline
  36 long v_read(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  37 {
  38         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  39         return uatomic_read(&v_a->a);
  40 }
  41
  42 static inline
  43 void v_set(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  44            long v)
  45 {
  46         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  47         uatomic_set(&v_a->a, v);
  48 }
  49
  50 static inline
  51 void v_add(const struct lttng_ust_lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  52 {
  53         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  54         uatomic_add(&v_a->a, v);
  55 }
  56
  57 static inline
  58 void v_inc(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  59 {
  60         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  61         uatomic_inc(&v_a->a);
  62 }
  63
  64 /*
  65  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  66  */
  67 static inline
  68 void _v_dec(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  69 {
  70         --v_a->v;
  71 }
  72
  73 static inline
  74 long v_cmpxchg(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  75                long old, long _new)
  76 {
  77         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  78         return uatomic_cmpxchg(&v_a->a, old, _new);
  79 }
  80
  81 #endif /* _LINUX_RING_BUFFER_VATOMIC_H */