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  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  25  * SOFTWARE.
  26  */
  27
  28 #include <assert.h>
  29 #include <urcu/uatomic.h>
  30
  31 /*
  32  * Same data type (long) accessed differently depending on configuration.
  33  * v field is for non-atomic access (protected by mutual exclusion).
  34  * In the fast-path, the ring_buffer_config structure is constant, so the
  35  * compiler can statically select the appropriate branch.
  36  * local_t is used for per-cpu and per-thread buffers.
  37  * atomic_long_t is used for globally shared buffers.
  38  */
  39 union v_atomic {
  40         long a; /* accessed through uatomic */
  41         long v;
  42 };
  43
  44 static inline
  45 long v_read(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  46 {
  47         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  48         return uatomic_read(&v_a->a);
  49 }
  50
  51 static inline
  52 void v_set(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  53            long v)
  54 {
  55         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  56         uatomic_set(&v_a->a, v);
  57 }
  58
  59 static inline
  60 void v_add(const struct lttng_ust_lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  61 {
  62         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  63         uatomic_add(&v_a->a, v);
  64 }
  65
  66 static inline
  67 void v_inc(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  68 {
  69         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  70         uatomic_inc(&v_a->a);
  71 }
  72
  73 /*
  74  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  75  */
  76 static inline
  77 void _v_dec(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a)
  78 {
  79         --v_a->v;
  80 }
  81
  82 static inline
  83 long v_cmpxchg(const struct lttng_ust_lib_ring_buffer_config *config, union v_atomic *v_a,
  84                long old, long _new)
  85 {
  86         assert(config->sync != RING_BUFFER_SYNC_PER_CPU);
  87         return uatomic_cmpxchg(&v_a->a, old, _new);
  88 }
  89
  90 #endif /* _LTTNG_RING_BUFFER_VATOMIC_H */