libringbuffer/frontend.h

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Ring Buffer Library Synchronization Header (API).
   7  *
   8  * See ring_buffer_frontend.c for more information on wait-free algorithms.
   9  */
  10
  11 #ifndef _LTTNG_RING_BUFFER_FRONTEND_H
  12 #define _LTTNG_RING_BUFFER_FRONTEND_H
  13
  14 #include <stddef.h>
  15 #include <stdint.h>
  16
  17 #include <urcu/compiler.h>
  18 #include <urcu/uatomic.h>
  19
  20 #include "smp.h"
  21
  22 /* Internal helpers */
  23 #include "frontend_internal.h"
  24
  25 /* Buffer creation/removal and setup operations */
  26
  27 /*
  28  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  29  * padding to let readers get those sub-buffers.  Used for live streaming.
  30  *
  31  * read_timer_interval is the time interval (in us) to wake up pending readers.
  32  *
  33  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  34  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  35  * be set to NULL for other backends.
  36  *
  37  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  38  * memory area for client-specific data. This memory is managed by lib
  39  * ring buffer. priv_data_align is the alignment required for the
  40  * private data area.
  41  */
  42
  43 __attribute__((visibility("hidden")))
  44 extern
  45 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  46                                 const char *name,
  47                                 void **priv_data,
  48                                 size_t priv_data_align,
  49                                 size_t priv_data_size,
  50                                 void *priv_data_init,
  51                                 void *buf_addr,
  52                                 size_t subbuf_size, size_t num_subbuf,
  53                                 unsigned int switch_timer_interval,
  54                                 unsigned int read_timer_interval,
  55                                 const int *stream_fds, int nr_stream_fds,
  56                                 int64_t blocking_timeout);
  57
  58 /*
  59  * channel_destroy finalizes all channel's buffers, waits for readers to
  60  * release all references, and destroys the channel.
  61  */
  62 __attribute__((visibility("hidden")))
  63 extern
  64 void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan,
  65                 struct lttng_ust_shm_handle *handle,
  66                 int consumer);
  67
  68
  69 /* Buffer read operations */
  70
  71 /*
  72  * Iteration on channel cpumask needs to issue a read barrier to match the write
  73  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  74  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  75  * only performed at channel destruction.
  76  */
  77 #define for_each_channel_cpu(cpu, chan)                                 \
  78         for_each_possible_cpu(cpu)
  79
  80 __attribute__((visibility("hidden")))
  81 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  82                                 const struct lttng_ust_lib_ring_buffer_config *config,
  83                                 struct lttng_ust_lib_ring_buffer_channel *chan, int cpu,
  84                                 struct lttng_ust_shm_handle *handle,
  85                                 int *shm_fd, int *wait_fd,
  86                                 int *wakeup_fd,
  87                                 uint64_t *memory_map_size);
  88
  89 __attribute__((visibility("hidden")))
  90 extern
  91 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  92                         struct lttng_ust_lib_ring_buffer_channel *chan,
  93                         struct lttng_ust_shm_handle *handle);
  94
  95 __attribute__((visibility("hidden")))
  96 extern
  97 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  98                         struct lttng_ust_lib_ring_buffer_channel *chan,
  99                         struct lttng_ust_shm_handle *handle);
 100
 101 __attribute__((visibility("hidden")))
 102 extern
 103 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 104                 struct lttng_ust_lib_ring_buffer_channel *chan,
 105                 struct lttng_ust_shm_handle *handle,
 106                 int cpu);
 107
 108 __attribute__((visibility("hidden")))
 109 extern
 110 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 111                 struct lttng_ust_lib_ring_buffer_channel *chan,
 112                 struct lttng_ust_shm_handle *handle,
 113                 int cpu);
 114
 115 __attribute__((visibility("hidden")))
 116 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 117                                      struct lttng_ust_shm_handle *handle);
 118
 119 __attribute__((visibility("hidden")))
 120 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 121                                          struct lttng_ust_shm_handle *handle);
 122
 123 /*
 124  * Initialize signals for ring buffer. Should be called early e.g. by
 125  * main() in the program to affect all threads.
 126  */
 127 __attribute__((visibility("hidden")))
 128 void lib_ringbuffer_signal_init(void);
 129
 130 /*
 131  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 132  */
 133 __attribute__((visibility("hidden")))
 134 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 135                                     unsigned long *consumed,
 136                                     unsigned long *produced,
 137                                     struct lttng_ust_shm_handle *handle);
 138
 139 __attribute__((visibility("hidden")))
 140 extern int lib_ring_buffer_snapshot_sample_positions(
 141                                     struct lttng_ust_lib_ring_buffer *buf,
 142                                     unsigned long *consumed,
 143                                     unsigned long *produced,
 144                                     struct lttng_ust_shm_handle *handle);
 145
 146 __attribute__((visibility("hidden")))
 147 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 148                                           unsigned long consumed_new,
 149                                           struct lttng_ust_shm_handle *handle);
 150
 151 __attribute__((visibility("hidden")))
 152 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 153                                       unsigned long consumed,
 154                                       struct lttng_ust_shm_handle *handle);
 155 __attribute__((visibility("hidden")))
 156 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 157                                        struct lttng_ust_shm_handle *handle);
 158
 159 /*
 160  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 161  * to read sub-buffers sequentially.
 162  */
 163 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 164                                                   struct lttng_ust_shm_handle *handle)
 165 {
 166         int ret;
 167
 168         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 169                                        &buf->prod_snapshot, handle);
 170         if (ret)
 171                 return ret;
 172         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 173         return ret;
 174 }
 175
 176 static inline
 177 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 178                                      struct lttng_ust_shm_handle *handle)
 179 {
 180         struct lttng_ust_lib_ring_buffer_channel *chan;
 181
 182         chan = shmp(handle, buf->backend.chan);
 183         if (!chan)
 184                 return;
 185         lib_ring_buffer_put_subbuf(buf, handle);
 186         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 187                         handle);
 188 }
 189
 190 __attribute__((visibility("hidden")))
 191 extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel *chan);
 192
 193 __attribute__((visibility("hidden")))
 194 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 195                                   struct lttng_ust_shm_handle *handle);
 196
 197 static inline
 198 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 199                                          struct lttng_ust_lib_ring_buffer *buf)
 200 {
 201         return v_read(config, &buf->offset);
 202 }
 203
 204 static inline
 205 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 206                                            struct lttng_ust_lib_ring_buffer *buf)
 207 {
 208         return uatomic_read(&buf->consumed);
 209 }
 210
 211 /*
 212  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 213  * ordering enforced with respect to trace teardown).
 214  */
 215 static inline
 216 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 217                                  struct lttng_ust_lib_ring_buffer *buf)
 218 {
 219         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 220         /*
 221          * Read finalized before counters.
 222          */
 223         cmm_smp_rmb();
 224         return finalized;
 225 }
 226
 227 static inline
 228 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel *chan)
 229 {
 230         return chan->finalized;
 231 }
 232
 233 static inline
 234 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel *chan)
 235 {
 236         return uatomic_read(&chan->record_disabled);
 237 }
 238
 239 static inline
 240 unsigned long lib_ring_buffer_get_read_data_size(
 241                                 const struct lttng_ust_lib_ring_buffer_config *config,
 242                                 struct lttng_ust_lib_ring_buffer *buf,
 243                                 struct lttng_ust_shm_handle *handle)
 244 {
 245         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 246 }
 247
 248 static inline
 249 unsigned long lib_ring_buffer_get_records_count(
 250                                 const struct lttng_ust_lib_ring_buffer_config *config,
 251                                 struct lttng_ust_lib_ring_buffer *buf)
 252 {
 253         return v_read(config, &buf->records_count);
 254 }
 255
 256 static inline
 257 unsigned long lib_ring_buffer_get_records_overrun(
 258                                 const struct lttng_ust_lib_ring_buffer_config *config,
 259                                 struct lttng_ust_lib_ring_buffer *buf)
 260 {
 261         return v_read(config, &buf->records_overrun);
 262 }
 263
 264 static inline
 265 unsigned long lib_ring_buffer_get_records_lost_full(
 266                                 const struct lttng_ust_lib_ring_buffer_config *config,
 267                                 struct lttng_ust_lib_ring_buffer *buf)
 268 {
 269         return v_read(config, &buf->records_lost_full);
 270 }
 271
 272 static inline
 273 unsigned long lib_ring_buffer_get_records_lost_wrap(
 274                                 const struct lttng_ust_lib_ring_buffer_config *config,
 275                                 struct lttng_ust_lib_ring_buffer *buf)
 276 {
 277         return v_read(config, &buf->records_lost_wrap);
 278 }
 279
 280 static inline
 281 unsigned long lib_ring_buffer_get_records_lost_big(
 282                                 const struct lttng_ust_lib_ring_buffer_config *config,
 283                                 struct lttng_ust_lib_ring_buffer *buf)
 284 {
 285         return v_read(config, &buf->records_lost_big);
 286 }
 287
 288 static inline
 289 unsigned long lib_ring_buffer_get_records_read(
 290                                 const struct lttng_ust_lib_ring_buffer_config *config,
 291                                 struct lttng_ust_lib_ring_buffer *buf)
 292 {
 293         return v_read(config, &buf->backend.records_read);
 294 }
 295
 296 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */