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 void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan,
  63                 struct lttng_ust_shm_handle *handle,
  64                 int consumer);
  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 __attribute__((visibility("hidden")))
  79 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  80                                 const struct lttng_ust_lib_ring_buffer_config *config,
  81                                 struct lttng_ust_lib_ring_buffer_channel *chan, int cpu,
  82                                 struct lttng_ust_shm_handle *handle,
  83                                 int *shm_fd, int *wait_fd,
  84                                 int *wakeup_fd,
  85                                 uint64_t *memory_map_size);
  86
  87 __attribute__((visibility("hidden")))
  88 extern
  89 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  90                         struct lttng_ust_lib_ring_buffer_channel *chan,
  91                         struct lttng_ust_shm_handle *handle);
  92
  93 __attribute__((visibility("hidden")))
  94 extern
  95 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  96                         struct lttng_ust_lib_ring_buffer_channel *chan,
  97                         struct lttng_ust_shm_handle *handle);
  98
  99 __attribute__((visibility("hidden")))
 100 extern
 101 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 102                 struct lttng_ust_lib_ring_buffer_channel *chan,
 103                 struct lttng_ust_shm_handle *handle,
 104                 int cpu);
 105
 106 __attribute__((visibility("hidden")))
 107 extern
 108 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 109                 struct lttng_ust_lib_ring_buffer_channel *chan,
 110                 struct lttng_ust_shm_handle *handle,
 111                 int cpu);
 112
 113 __attribute__((visibility("hidden")))
 114 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 115                                      struct lttng_ust_shm_handle *handle);
 116
 117 __attribute__((visibility("hidden")))
 118 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 119                                          struct lttng_ust_shm_handle *handle);
 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 __attribute__((visibility("hidden")))
 126 void lib_ringbuffer_signal_init(void);
 127
 128 /*
 129  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 130  */
 131 __attribute__((visibility("hidden")))
 132 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 133                                     unsigned long *consumed,
 134                                     unsigned long *produced,
 135                                     struct lttng_ust_shm_handle *handle);
 136
 137 __attribute__((visibility("hidden")))
 138 extern int lib_ring_buffer_snapshot_sample_positions(
 139                                     struct lttng_ust_lib_ring_buffer *buf,
 140                                     unsigned long *consumed,
 141                                     unsigned long *produced,
 142                                     struct lttng_ust_shm_handle *handle);
 143
 144 __attribute__((visibility("hidden")))
 145 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 146                                           unsigned long consumed_new,
 147                                           struct lttng_ust_shm_handle *handle);
 148
 149 __attribute__((visibility("hidden")))
 150 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 151                                       unsigned long consumed,
 152                                       struct lttng_ust_shm_handle *handle);
 153 __attribute__((visibility("hidden")))
 154 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 155                                        struct lttng_ust_shm_handle *handle);
 156
 157 /*
 158  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 159  * to read sub-buffers sequentially.
 160  */
 161 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 162                                                   struct lttng_ust_shm_handle *handle)
 163 {
 164         int ret;
 165
 166         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 167                                        &buf->prod_snapshot, handle);
 168         if (ret)
 169                 return ret;
 170         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 171         return ret;
 172 }
 173
 174 static inline
 175 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 176                                      struct lttng_ust_shm_handle *handle)
 177 {
 178         struct lttng_ust_lib_ring_buffer_channel *chan;
 179
 180         chan = shmp(handle, buf->backend.chan);
 181         if (!chan)
 182                 return;
 183         lib_ring_buffer_put_subbuf(buf, handle);
 184         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 185                         handle);
 186 }
 187
 188 __attribute__((visibility("hidden")))
 189 extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel *chan);
 190
 191 __attribute__((visibility("hidden")))
 192 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 193                                   struct lttng_ust_shm_handle *handle);
 194
 195 static inline
 196 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 197                                          struct lttng_ust_lib_ring_buffer *buf)
 198 {
 199         return v_read(config, &buf->offset);
 200 }
 201
 202 static inline
 203 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 204                                            struct lttng_ust_lib_ring_buffer *buf)
 205 {
 206         return uatomic_read(&buf->consumed);
 207 }
 208
 209 /*
 210  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 211  * ordering enforced with respect to trace teardown).
 212  */
 213 static inline
 214 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 215                                  struct lttng_ust_lib_ring_buffer *buf)
 216 {
 217         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 218         /*
 219          * Read finalized before counters.
 220          */
 221         cmm_smp_rmb();
 222         return finalized;
 223 }
 224
 225 static inline
 226 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel *chan)
 227 {
 228         return chan->finalized;
 229 }
 230
 231 static inline
 232 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel *chan)
 233 {
 234         return uatomic_read(&chan->record_disabled);
 235 }
 236
 237 static inline
 238 unsigned long lib_ring_buffer_get_read_data_size(
 239                                 const struct lttng_ust_lib_ring_buffer_config *config,
 240                                 struct lttng_ust_lib_ring_buffer *buf,
 241                                 struct lttng_ust_shm_handle *handle)
 242 {
 243         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 244 }
 245
 246 static inline
 247 unsigned long lib_ring_buffer_get_records_count(
 248                                 const struct lttng_ust_lib_ring_buffer_config *config,
 249                                 struct lttng_ust_lib_ring_buffer *buf)
 250 {
 251         return v_read(config, &buf->records_count);
 252 }
 253
 254 static inline
 255 unsigned long lib_ring_buffer_get_records_overrun(
 256                                 const struct lttng_ust_lib_ring_buffer_config *config,
 257                                 struct lttng_ust_lib_ring_buffer *buf)
 258 {
 259         return v_read(config, &buf->records_overrun);
 260 }
 261
 262 static inline
 263 unsigned long lib_ring_buffer_get_records_lost_full(
 264                                 const struct lttng_ust_lib_ring_buffer_config *config,
 265                                 struct lttng_ust_lib_ring_buffer *buf)
 266 {
 267         return v_read(config, &buf->records_lost_full);
 268 }
 269
 270 static inline
 271 unsigned long lib_ring_buffer_get_records_lost_wrap(
 272                                 const struct lttng_ust_lib_ring_buffer_config *config,
 273                                 struct lttng_ust_lib_ring_buffer *buf)
 274 {
 275         return v_read(config, &buf->records_lost_wrap);
 276 }
 277
 278 static inline
 279 unsigned long lib_ring_buffer_get_records_lost_big(
 280                                 const struct lttng_ust_lib_ring_buffer_config *config,
 281                                 struct lttng_ust_lib_ring_buffer *buf)
 282 {
 283         return v_read(config, &buf->records_lost_big);
 284 }
 285
 286 static inline
 287 unsigned long lib_ring_buffer_get_records_read(
 288                                 const struct lttng_ust_lib_ring_buffer_config *config,
 289                                 struct lttng_ust_lib_ring_buffer *buf)
 290 {
 291         return v_read(config, &buf->backend.records_read);
 292 }
 293
 294 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */