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  * private data is a memory area for configuration data. This memory is
  38  * managed by lib ring buffer. priv_data_align is the alignment required
  39  * for the private data area.
  40  */
  41
  42 __attribute__((visibility("hidden")))
  43 extern
  44 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  45                                 const char *name,
  46                                 size_t priv_data_align,
  47                                 size_t priv_data_size,
  48                                 void *priv_data_init,
  49                                 void *priv,
  50                                 void *buf_addr,
  51                                 size_t subbuf_size, size_t num_subbuf,
  52                                 unsigned int switch_timer_interval,
  53                                 unsigned int read_timer_interval,
  54                                 const int *stream_fds, int nr_stream_fds,
  55                                 int64_t blocking_timeout);
  56
  57 /*
  58  * channel_destroy finalizes all channel's buffers, waits for readers to
  59  * release all references, and destroys the channel.
  60  */
  61 __attribute__((visibility("hidden")))
  62 extern
  63 void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan,
  64                 struct lttng_ust_shm_handle *handle,
  65                 int consumer);
  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 __attribute__((visibility("hidden")))
  80 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  81                                 const struct lttng_ust_lib_ring_buffer_config *config,
  82                                 struct lttng_ust_lib_ring_buffer_channel *chan, int cpu,
  83                                 struct lttng_ust_shm_handle *handle,
  84                                 int *shm_fd, int *wait_fd,
  85                                 int *wakeup_fd,
  86                                 uint64_t *memory_map_size);
  87
  88 __attribute__((visibility("hidden")))
  89 extern
  90 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  91                         struct lttng_ust_lib_ring_buffer_channel *chan,
  92                         struct lttng_ust_shm_handle *handle);
  93
  94 __attribute__((visibility("hidden")))
  95 extern
  96 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  97                         struct lttng_ust_lib_ring_buffer_channel *chan,
  98                         struct lttng_ust_shm_handle *handle);
  99
 100 __attribute__((visibility("hidden")))
 101 extern
 102 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 103                 struct lttng_ust_lib_ring_buffer_channel *chan,
 104                 struct lttng_ust_shm_handle *handle,
 105                 int cpu);
 106
 107 __attribute__((visibility("hidden")))
 108 extern
 109 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 110                 struct lttng_ust_lib_ring_buffer_channel *chan,
 111                 struct lttng_ust_shm_handle *handle,
 112                 int cpu);
 113
 114 __attribute__((visibility("hidden")))
 115 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 116                                      struct lttng_ust_shm_handle *handle);
 117
 118 __attribute__((visibility("hidden")))
 119 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 120                                          struct lttng_ust_shm_handle *handle);
 121
 122 /*
 123  * Initialize signals for ring buffer. Should be called early e.g. by
 124  * main() in the program to affect all threads.
 125  */
 126 __attribute__((visibility("hidden")))
 127 void lib_ringbuffer_signal_init(void);
 128
 129 /*
 130  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 131  */
 132 __attribute__((visibility("hidden")))
 133 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 134                                     unsigned long *consumed,
 135                                     unsigned long *produced,
 136                                     struct lttng_ust_shm_handle *handle);
 137
 138 __attribute__((visibility("hidden")))
 139 extern int lib_ring_buffer_snapshot_sample_positions(
 140                                     struct lttng_ust_lib_ring_buffer *buf,
 141                                     unsigned long *consumed,
 142                                     unsigned long *produced,
 143                                     struct lttng_ust_shm_handle *handle);
 144
 145 __attribute__((visibility("hidden")))
 146 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 147                                           unsigned long consumed_new,
 148                                           struct lttng_ust_shm_handle *handle);
 149
 150 __attribute__((visibility("hidden")))
 151 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 152                                       unsigned long consumed,
 153                                       struct lttng_ust_shm_handle *handle);
 154 __attribute__((visibility("hidden")))
 155 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 156                                        struct lttng_ust_shm_handle *handle);
 157
 158 /*
 159  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 160  * to read sub-buffers sequentially.
 161  */
 162 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 163                                                   struct lttng_ust_shm_handle *handle)
 164 {
 165         int ret;
 166
 167         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 168                                        &buf->prod_snapshot, handle);
 169         if (ret)
 170                 return ret;
 171         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 172         return ret;
 173 }
 174
 175 static inline
 176 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 177                                      struct lttng_ust_shm_handle *handle)
 178 {
 179         struct lttng_ust_lib_ring_buffer_channel *chan;
 180
 181         chan = shmp(handle, buf->backend.chan);
 182         if (!chan)
 183                 return;
 184         lib_ring_buffer_put_subbuf(buf, handle);
 185         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 186                         handle);
 187 }
 188
 189 __attribute__((visibility("hidden")))
 190 extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel *chan);
 191
 192 __attribute__((visibility("hidden")))
 193 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 194                                   struct lttng_ust_shm_handle *handle);
 195
 196 static inline
 197 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 198                                          struct lttng_ust_lib_ring_buffer *buf)
 199 {
 200         return v_read(config, &buf->offset);
 201 }
 202
 203 static inline
 204 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 205                                            struct lttng_ust_lib_ring_buffer *buf)
 206 {
 207         return uatomic_read(&buf->consumed);
 208 }
 209
 210 /*
 211  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 212  * ordering enforced with respect to trace teardown).
 213  */
 214 static inline
 215 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 216                                  struct lttng_ust_lib_ring_buffer *buf)
 217 {
 218         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 219         /*
 220          * Read finalized before counters.
 221          */
 222         cmm_smp_rmb();
 223         return finalized;
 224 }
 225
 226 static inline
 227 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel *chan)
 228 {
 229         return chan->finalized;
 230 }
 231
 232 static inline
 233 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel *chan)
 234 {
 235         return uatomic_read(&chan->record_disabled);
 236 }
 237
 238 static inline
 239 unsigned long lib_ring_buffer_get_read_data_size(
 240                                 const struct lttng_ust_lib_ring_buffer_config *config,
 241                                 struct lttng_ust_lib_ring_buffer *buf,
 242                                 struct lttng_ust_shm_handle *handle)
 243 {
 244         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 245 }
 246
 247 static inline
 248 unsigned long lib_ring_buffer_get_records_count(
 249                                 const struct lttng_ust_lib_ring_buffer_config *config,
 250                                 struct lttng_ust_lib_ring_buffer *buf)
 251 {
 252         return v_read(config, &buf->records_count);
 253 }
 254
 255 static inline
 256 unsigned long lib_ring_buffer_get_records_overrun(
 257                                 const struct lttng_ust_lib_ring_buffer_config *config,
 258                                 struct lttng_ust_lib_ring_buffer *buf)
 259 {
 260         return v_read(config, &buf->records_overrun);
 261 }
 262
 263 static inline
 264 unsigned long lib_ring_buffer_get_records_lost_full(
 265                                 const struct lttng_ust_lib_ring_buffer_config *config,
 266                                 struct lttng_ust_lib_ring_buffer *buf)
 267 {
 268         return v_read(config, &buf->records_lost_full);
 269 }
 270
 271 static inline
 272 unsigned long lib_ring_buffer_get_records_lost_wrap(
 273                                 const struct lttng_ust_lib_ring_buffer_config *config,
 274                                 struct lttng_ust_lib_ring_buffer *buf)
 275 {
 276         return v_read(config, &buf->records_lost_wrap);
 277 }
 278
 279 static inline
 280 unsigned long lib_ring_buffer_get_records_lost_big(
 281                                 const struct lttng_ust_lib_ring_buffer_config *config,
 282                                 struct lttng_ust_lib_ring_buffer *buf)
 283 {
 284         return v_read(config, &buf->records_lost_big);
 285 }
 286
 287 static inline
 288 unsigned long lib_ring_buffer_get_records_read(
 289                                 const struct lttng_ust_lib_ring_buffer_config *config,
 290                                 struct lttng_ust_lib_ring_buffer *buf)
 291 {
 292         return v_read(config, &buf->backend.records_read);
 293 }
 294
 295 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */