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 extern
  43 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  44                                 const char *name,
  45                                 size_t priv_data_align,
  46                                 size_t priv_data_size,
  47                                 void *priv_data_init,
  48                                 void *priv,
  49                                 void *buf_addr,
  50                                 size_t subbuf_size, size_t num_subbuf,
  51                                 unsigned int switch_timer_interval,
  52                                 unsigned int read_timer_interval,
  53                                 const int *stream_fds, int nr_stream_fds,
  54                                 int64_t blocking_timeout)
  55         __attribute__((visibility("hidden")));
  56
  57 /*
  58  * channel_destroy finalizes all channel's buffers, waits for readers to
  59  * release all references, and destroys the channel.
  60  */
  61 void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan,
  62                 struct lttng_ust_shm_handle *handle,
  63                 int consumer)
  64         __attribute__((visibility("hidden")));
  65
  66
  67 /* Buffer read operations */
  68
  69 /*
  70  * Iteration on channel cpumask needs to issue a read barrier to match the write
  71  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  72  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  73  * only performed at channel destruction.
  74  */
  75 #define for_each_channel_cpu(cpu, chan)                                 \
  76         for_each_possible_cpu(cpu)
  77
  78 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  79                                 const struct lttng_ust_lib_ring_buffer_config *config,
  80                                 struct lttng_ust_lib_ring_buffer_channel *chan, int cpu,
  81                                 struct lttng_ust_shm_handle *handle,
  82                                 int *shm_fd, int *wait_fd,
  83                                 int *wakeup_fd,
  84                                 uint64_t *memory_map_size)
  85         __attribute__((visibility("hidden")));
  86
  87 extern
  88 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  89                         struct lttng_ust_lib_ring_buffer_channel *chan,
  90                         struct lttng_ust_shm_handle *handle)
  91         __attribute__((visibility("hidden")));
  92
  93 extern
  94 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  95                         struct lttng_ust_lib_ring_buffer_channel *chan,
  96                         struct lttng_ust_shm_handle *handle)
  97         __attribute__((visibility("hidden")));
  98
  99 extern
 100 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 101                 struct lttng_ust_lib_ring_buffer_channel *chan,
 102                 struct lttng_ust_shm_handle *handle,
 103                 int cpu)
 104         __attribute__((visibility("hidden")));
 105
 106 extern
 107 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 108                 struct lttng_ust_lib_ring_buffer_channel *chan,
 109                 struct lttng_ust_shm_handle *handle,
 110                 int cpu)
 111         __attribute__((visibility("hidden")));
 112
 113 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 114                                      struct lttng_ust_shm_handle *handle)
 115         __attribute__((visibility("hidden")));
 116
 117 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 118                                          struct lttng_ust_shm_handle *handle)
 119         __attribute__((visibility("hidden")));
 120
 121 /*
 122  * Initialize signals for ring buffer. Should be called early e.g. by
 123  * main() in the program to affect all threads.
 124  */
 125 void lib_ringbuffer_signal_init(void)
 126         __attribute__((visibility("hidden")));
 127
 128 /*
 129  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 130  */
 131 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 132                                     unsigned long *consumed,
 133                                     unsigned long *produced,
 134                                     struct lttng_ust_shm_handle *handle)
 135         __attribute__((visibility("hidden")));
 136
 137 extern int lib_ring_buffer_snapshot_sample_positions(
 138                                     struct lttng_ust_lib_ring_buffer *buf,
 139                                     unsigned long *consumed,
 140                                     unsigned long *produced,
 141                                     struct lttng_ust_shm_handle *handle)
 142         __attribute__((visibility("hidden")));
 143
 144 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 145                                           unsigned long consumed_new,
 146                                           struct lttng_ust_shm_handle *handle)
 147         __attribute__((visibility("hidden")));
 148
 149 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 150                                       unsigned long consumed,
 151                                       struct lttng_ust_shm_handle *handle)
 152         __attribute__((visibility("hidden")));
 153
 154 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 155                                        struct lttng_ust_shm_handle *handle)
 156         __attribute__((visibility("hidden")));
 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 extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel *chan)
 190         __attribute__((visibility("hidden")));
 191
 192 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 193                                   struct lttng_ust_shm_handle *handle)
 194         __attribute__((visibility("hidden")));
 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(
 205                 const struct lttng_ust_lib_ring_buffer_config *config __attribute__((unused)),
 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(
 217                 const struct lttng_ust_lib_ring_buffer_config *config __attribute__((unused)),
 218                  struct lttng_ust_lib_ring_buffer *buf)
 219 {
 220         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 221         /*
 222          * Read finalized before counters.
 223          */
 224         cmm_smp_rmb();
 225         return finalized;
 226 }
 227
 228 static inline
 229 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel *chan)
 230 {
 231         return chan->finalized;
 232 }
 233
 234 static inline
 235 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel *chan)
 236 {
 237         return uatomic_read(&chan->record_disabled);
 238 }
 239
 240 static inline
 241 unsigned long lib_ring_buffer_get_read_data_size(
 242                                 const struct lttng_ust_lib_ring_buffer_config *config,
 243                                 struct lttng_ust_lib_ring_buffer *buf,
 244                                 struct lttng_ust_shm_handle *handle)
 245 {
 246         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 247 }
 248
 249 static inline
 250 unsigned long lib_ring_buffer_get_records_count(
 251                                 const struct lttng_ust_lib_ring_buffer_config *config,
 252                                 struct lttng_ust_lib_ring_buffer *buf)
 253 {
 254         return v_read(config, &buf->records_count);
 255 }
 256
 257 static inline
 258 unsigned long lib_ring_buffer_get_records_overrun(
 259                                 const struct lttng_ust_lib_ring_buffer_config *config,
 260                                 struct lttng_ust_lib_ring_buffer *buf)
 261 {
 262         return v_read(config, &buf->records_overrun);
 263 }
 264
 265 static inline
 266 unsigned long lib_ring_buffer_get_records_lost_full(
 267                                 const struct lttng_ust_lib_ring_buffer_config *config,
 268                                 struct lttng_ust_lib_ring_buffer *buf)
 269 {
 270         return v_read(config, &buf->records_lost_full);
 271 }
 272
 273 static inline
 274 unsigned long lib_ring_buffer_get_records_lost_wrap(
 275                                 const struct lttng_ust_lib_ring_buffer_config *config,
 276                                 struct lttng_ust_lib_ring_buffer *buf)
 277 {
 278         return v_read(config, &buf->records_lost_wrap);
 279 }
 280
 281 static inline
 282 unsigned long lib_ring_buffer_get_records_lost_big(
 283                                 const struct lttng_ust_lib_ring_buffer_config *config,
 284                                 struct lttng_ust_lib_ring_buffer *buf)
 285 {
 286         return v_read(config, &buf->records_lost_big);
 287 }
 288
 289 static inline
 290 unsigned long lib_ring_buffer_get_records_read(
 291                                 const struct lttng_ust_lib_ring_buffer_config *config,
 292                                 struct lttng_ust_lib_ring_buffer *buf)
 293 {
 294         return v_read(config, &buf->backend.records_read);
 295 }
 296
 297 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */