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                                 int *shm_fd, int *wait_fd,
  47                                 uint64_t *memory_map_size);
  48
  49 /* channel_handle_create - for consumer. */
  50 extern
  51 struct shm_handle *channel_handle_create(int shm_fd, int wait_fd,
  52                                         uint64_t memory_map_size);
  53
  54 /* channel_handle_add_stream - for consumer. */
  55 extern
  56 int channel_handle_add_stream(struct shm_handle *handle,
  57                 int shm_fd, int wait_fd, uint64_t memory_map_size);
  58
  59 /*
  60  * channel_destroy returns the private data pointer. It finalizes all channel's
  61  * buffers, waits for readers to release all references, and destroys the
  62  * channel.
  63  */
  64 extern
  65 void *channel_destroy(struct channel *chan, struct shm_handle *handle);
  66
  67
  68 /* Buffer read operations */
  69
  70 /*
  71  * Iteration on channel cpumask needs to issue a read barrier to match the write
  72  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  73  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  74  * only performed at channel destruction.
  75  */
  76 #define for_each_channel_cpu(cpu, chan)                                 \
  77         for_each_possible_cpu(cpu)
  78
  79 extern struct lib_ring_buffer *channel_get_ring_buffer(
  80                                 const struct lib_ring_buffer_config *config,
  81                                 struct channel *chan, int cpu,
  82                                 struct shm_handle *handle,
  83                                 int *shm_fd, int *wait_fd,
  84                                 uint64_t *memory_map_size);
  85 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf,
  86                                      struct shm_handle *handle);
  87 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf,
  88                                          struct shm_handle *handle);
  89
  90 /*
  91  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  92  */
  93 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
  94                                     unsigned long *consumed,
  95                                     unsigned long *produced,
  96                                     struct shm_handle *handle);
  97 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
  98                                           unsigned long consumed_new,
  99                                           struct shm_handle *handle);
 100
 101 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
 102                                       unsigned long consumed,
 103                                       struct shm_handle *handle);
 104 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf,
 105                                        struct shm_handle *handle);
 106
 107 /*
 108  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 109  * to read sub-buffers sequentially.
 110  */
 111 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf,
 112                                                   struct shm_handle *handle)
 113 {
 114         int ret;
 115
 116         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 117                                        &buf->prod_snapshot, handle);
 118         if (ret)
 119                 return ret;
 120         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 121         return ret;
 122 }
 123
 124 static inline
 125 void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf,
 126                                      struct shm_handle *handle)
 127 {
 128         lib_ring_buffer_put_subbuf(buf, handle);
 129         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 130                                                         shmp(handle, buf->backend.chan)), handle);
 131 }
 132
 133 extern void channel_reset(struct channel *chan);
 134 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf,
 135                                   struct shm_handle *handle);
 136
 137 static inline
 138 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 139                                          struct lib_ring_buffer *buf)
 140 {
 141         return v_read(config, &buf->offset);
 142 }
 143
 144 static inline
 145 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 146                                            struct lib_ring_buffer *buf)
 147 {
 148         return uatomic_read(&buf->consumed);
 149 }
 150
 151 /*
 152  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 153  * ordering enforced with respect to trace teardown).
 154  */
 155 static inline
 156 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 157                                  struct lib_ring_buffer *buf)
 158 {
 159         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 160         /*
 161          * Read finalized before counters.
 162          */
 163         cmm_smp_rmb();
 164         return finalized;
 165 }
 166
 167 static inline
 168 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 169 {
 170         return chan->finalized;
 171 }
 172
 173 static inline
 174 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 175 {
 176         return uatomic_read(&chan->record_disabled);
 177 }
 178
 179 static inline
 180 unsigned long lib_ring_buffer_get_read_data_size(
 181                                 const struct lib_ring_buffer_config *config,
 182                                 struct lib_ring_buffer *buf,
 183                                 struct shm_handle *handle)
 184 {
 185         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 186 }
 187
 188 static inline
 189 unsigned long lib_ring_buffer_get_records_count(
 190                                 const struct lib_ring_buffer_config *config,
 191                                 struct lib_ring_buffer *buf)
 192 {
 193         return v_read(config, &buf->records_count);
 194 }
 195
 196 static inline
 197 unsigned long lib_ring_buffer_get_records_overrun(
 198                                 const struct lib_ring_buffer_config *config,
 199                                 struct lib_ring_buffer *buf)
 200 {
 201         return v_read(config, &buf->records_overrun);
 202 }
 203
 204 static inline
 205 unsigned long lib_ring_buffer_get_records_lost_full(
 206                                 const struct lib_ring_buffer_config *config,
 207                                 struct lib_ring_buffer *buf)
 208 {
 209         return v_read(config, &buf->records_lost_full);
 210 }
 211
 212 static inline
 213 unsigned long lib_ring_buffer_get_records_lost_wrap(
 214                                 const struct lib_ring_buffer_config *config,
 215                                 struct lib_ring_buffer *buf)
 216 {
 217         return v_read(config, &buf->records_lost_wrap);
 218 }
 219
 220 static inline
 221 unsigned long lib_ring_buffer_get_records_lost_big(
 222                                 const struct lib_ring_buffer_config *config,
 223                                 struct lib_ring_buffer *buf)
 224 {
 225         return v_read(config, &buf->records_lost_big);
 226 }
 227
 228 static inline
 229 unsigned long lib_ring_buffer_get_records_read(
 230                                 const struct lib_ring_buffer_config *config,
 231                                 struct lib_ring_buffer *buf)
 232 {
 233         return v_read(config, &buf->backend.records_read);
 234 }
 235
 236 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */