libringbuffer/vatomic.h

   1 #ifndef _LTTNG_RING_BUFFER_VATOMIC_H
   2 #define _LTTNG_RING_BUFFER_VATOMIC_H
   3
   4 /*
   5  * libringbuffer/vatomic.h
   6  *
   7  * Copyright (C) 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a copy
  10  * of this software and associated documentation files (the "Software"), to deal
  11  * in the Software without restriction, including without limitation the rights
  12  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13  * copies of the Software, and to permit persons to whom the Software is
  14  * furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included in
  17  * all copies or substantial portions of the Software.
  18  */
  19
  20 #include <assert.h>
  21 #include <urcu/uatomic.h>
  22
  23 /*
  24  * Same data type (long) accessed differently depending on configuration.
  25  * v field is for non-atomic access (protected by mutual exclusion).
  26  * In the fast-path, the ring_buffer_config structure is constant, so the
  27  * compiler can statically select the appropriate branch.
  28  * local_t is used for per-cpu and per-thread buffers.
  29  * atomic_long_t is used for globally shared buffers.
  30  */
  31 union v_atomic {
  32         long a; /* accessed through uatomic */
  33         long v;
  34 };
  35
  36 static inline
  37 long v_read(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  38 {
  39         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  40         return uatomic_read(&v_a->a);
  41 }
  42
  43 static inline
  44 void v_set(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  45            long v)
  46 {
  47         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  48         uatomic_set(&v_a->a, v);
  49 }
  50
  51 static inline
  52 void v_add(const struct lttng_ust_lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  53 {
  54         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  55         uatomic_add(&v_a->a, v);
  56 }
  57
  58 static inline
  59 void v_inc(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  60 {
  61         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  62         uatomic_inc(&v_a->a);
  63 }
  64
  65 /*
  66  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  67  */
  68 static inline
  69 void _v_dec(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  70 {
  71         --v_a->v;
  72 }
  73
  74 static inline
  75 long v_cmpxchg(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  76                long old, long _new)
  77 {
  78         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  79         return uatomic_cmpxchg(&v_a->a, old, _new);
  80 }
  81
  82 #endif /* _LTTNG_RING_BUFFER_VATOMIC_H */