include/ust/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 <assert.h>
  13 #include <urcu/uatomic.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         long a; /* accessed through uatomic */
  25         long v;
  26 };
  27
  28 static inline
  29 long v_read(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  30 {
  31         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  32         return uatomic_read(&v_a->a);
  33 }
  34
  35 static inline
  36 void v_set(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  37            long v)
  38 {
  39         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  40         uatomic_set(&v_a->a, v);
  41 }
  42
  43 static inline
  44 void v_add(const struct lttng_ust_lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  45 {
  46         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  47         uatomic_add(&v_a->a, v);
  48 }
  49
  50 static inline
  51 void v_inc(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  52 {
  53         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  54         uatomic_inc(&v_a->a);
  55 }
  56
  57 /*
  58  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  59  */
  60 static inline
  61 void _v_dec(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  62 {
  63         --v_a->v;
  64 }
  65
  66 static inline
  67 long v_cmpxchg(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  68                long old, long _new)
  69 {
  70         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  71         return uatomic_cmpxchg(&v_a->a, old, _new);
  72 }
  73
  74 #endif /* _LINUX_RING_BUFFER_VATOMIC_H */