libringbuffer/frontend.h

   1 #ifndef _LINUX_RING_BUFFER_FRONTEND_H
   2 #define _LINUX_RING_BUFFER_FRONTEND_H
   3
   4 /*
   5  * linux/ringbuffer/frontend.h
   6  *
   7  * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Ring Buffer Library Synchronization Header (API).
  10  *
  11  * Author:
  12  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  13  *
  14  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  15  *
  16  * Dual LGPL v2.1/GPL v2 license.
  17  */
  18
  19 #include <urcu/compiler.h>
  20 #include <urcu/uatomic.h>
  21
  22 #include "smp.h"
  23 /* Internal helpers */
  24 #include "frontend_internal.h"
  25
  26 /* Buffer creation/removal and setup operations */
  27
  28 /*
  29  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  30  * padding to let readers get those sub-buffers.  Used for live streaming.
  31  *
  32  * read_timer_interval is the time interval (in us) to wake up pending readers.
  33  *
  34  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  35  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  36  * be set to NULL for other backends.
  37  */
  38
  39 extern
  40 struct shm_handle *channel_create(const struct lib_ring_buffer_config *config,
  41                                 const char *name, void *priv,
  42                                 void *buf_addr,
  43                                 size_t subbuf_size, size_t num_subbuf,
  44                                 unsigned int switch_timer_interval,
  45                                 unsigned int read_timer_interval);
  46
  47 /*
  48  * channel_destroy returns the private data pointer. It finalizes all channel's
  49  * buffers, waits for readers to release all references, and destroys the
  50  * channel.
  51  */
  52 extern
  53 void *channel_destroy(struct channel *chan, struct shm_handle *handle);
  54
  55
  56 /* Buffer read operations */
  57
  58 /*
  59  * Iteration on channel cpumask needs to issue a read barrier to match the write
  60  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  61  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  62  * only performed at channel destruction.
  63  */
  64 #define for_each_channel_cpu(cpu, chan)                                 \
  65         for_each_possible_cpu(cpu)
  66
  67 extern struct lib_ring_buffer *channel_get_ring_buffer(
  68                                 const struct lib_ring_buffer_config *config,
  69                                 struct channel *chan, int cpu,
  70                                 struct shm_handle *handle);
  71 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf,
  72                                      struct shm_handle *handle);
  73 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf,
  74                                          struct shm_handle *handle);
  75
  76 /*
  77  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  78  */
  79 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
  80                                     unsigned long *consumed,
  81                                     unsigned long *produced,
  82                                     struct shm_handle *handle);
  83 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
  84                                           unsigned long consumed_new,
  85                                           struct shm_handle *handle);
  86
  87 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
  88                                       unsigned long consumed,
  89                                       struct shm_handle *handle);
  90 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf,
  91                                        struct shm_handle *handle);
  92
  93 /*
  94  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
  95  * to read sub-buffers sequentially.
  96  */
  97 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf,
  98                                                   struct shm_handle *handle)
  99 {
 100         int ret;
 101
 102         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 103                                        &buf->prod_snapshot, handle);
 104         if (ret)
 105                 return ret;
 106         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 107         return ret;
 108 }
 109
 110 static inline
 111 void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf,
 112                                      struct shm_handle *handle)
 113 {
 114         lib_ring_buffer_put_subbuf(buf, handle);
 115         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 116                                                         shmp(handle, buf->backend.chan)), handle);
 117 }
 118
 119 extern void channel_reset(struct channel *chan);
 120 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf,
 121                                   struct shm_handle *handle);
 122
 123 static inline
 124 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 125                                          struct lib_ring_buffer *buf)
 126 {
 127         return v_read(config, &buf->offset);
 128 }
 129
 130 static inline
 131 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 132                                            struct lib_ring_buffer *buf)
 133 {
 134         return uatomic_read(&buf->consumed);
 135 }
 136
 137 /*
 138  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 139  * ordering enforced with respect to trace teardown).
 140  */
 141 static inline
 142 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 143                                  struct lib_ring_buffer *buf)
 144 {
 145         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 146         /*
 147          * Read finalized before counters.
 148          */
 149         cmm_smp_rmb();
 150         return finalized;
 151 }
 152
 153 static inline
 154 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 155 {
 156         return chan->finalized;
 157 }
 158
 159 static inline
 160 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 161 {
 162         return uatomic_read(&chan->record_disabled);
 163 }
 164
 165 static inline
 166 unsigned long lib_ring_buffer_get_read_data_size(
 167                                 const struct lib_ring_buffer_config *config,
 168                                 struct lib_ring_buffer *buf,
 169                                 struct shm_handle *handle)
 170 {
 171         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 172 }
 173
 174 static inline
 175 unsigned long lib_ring_buffer_get_records_count(
 176                                 const struct lib_ring_buffer_config *config,
 177                                 struct lib_ring_buffer *buf)
 178 {
 179         return v_read(config, &buf->records_count);
 180 }
 181
 182 static inline
 183 unsigned long lib_ring_buffer_get_records_overrun(
 184                                 const struct lib_ring_buffer_config *config,
 185                                 struct lib_ring_buffer *buf)
 186 {
 187         return v_read(config, &buf->records_overrun);
 188 }
 189
 190 static inline
 191 unsigned long lib_ring_buffer_get_records_lost_full(
 192                                 const struct lib_ring_buffer_config *config,
 193                                 struct lib_ring_buffer *buf)
 194 {
 195         return v_read(config, &buf->records_lost_full);
 196 }
 197
 198 static inline
 199 unsigned long lib_ring_buffer_get_records_lost_wrap(
 200                                 const struct lib_ring_buffer_config *config,
 201                                 struct lib_ring_buffer *buf)
 202 {
 203         return v_read(config, &buf->records_lost_wrap);
 204 }
 205
 206 static inline
 207 unsigned long lib_ring_buffer_get_records_lost_big(
 208                                 const struct lib_ring_buffer_config *config,
 209                                 struct lib_ring_buffer *buf)
 210 {
 211         return v_read(config, &buf->records_lost_big);
 212 }
 213
 214 static inline
 215 unsigned long lib_ring_buffer_get_records_read(
 216                                 const struct lib_ring_buffer_config *config,
 217                                 struct lib_ring_buffer *buf)
 218 {
 219         return v_read(config, &buf->backend.records_read);
 220 }
 221
 222 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */