src/common/ringbuffer/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 "common/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_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_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_ring_buffer *channel_get_ring_buffer(
  79                                 const struct lttng_ust_ring_buffer_config *config,
  80                                 struct lttng_ust_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                                 void **memory_map_addr)
  86         __attribute__((visibility("hidden")));
  87
  88 extern
  89 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_ring_buffer_config *config,
  90                         struct lttng_ust_ring_buffer_channel *chan,
  91                         struct lttng_ust_shm_handle *handle)
  92         __attribute__((visibility("hidden")));
  93
  94 extern
  95 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_ring_buffer_config *config,
  96                         struct lttng_ust_ring_buffer_channel *chan,
  97                         struct lttng_ust_shm_handle *handle)
  98         __attribute__((visibility("hidden")));
  99
 100 extern
 101 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_ring_buffer_config *config,
 102                 struct lttng_ust_ring_buffer_channel *chan,
 103                 struct lttng_ust_shm_handle *handle,
 104                 int cpu)
 105         __attribute__((visibility("hidden")));
 106
 107 extern
 108 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_ring_buffer_config *config,
 109                 struct lttng_ust_ring_buffer_channel *chan,
 110                 struct lttng_ust_shm_handle *handle,
 111                 int cpu)
 112         __attribute__((visibility("hidden")));
 113
 114 extern int lib_ring_buffer_open_read(struct lttng_ust_ring_buffer *buf,
 115                                      struct lttng_ust_shm_handle *handle)
 116         __attribute__((visibility("hidden")));
 117
 118 extern void lib_ring_buffer_release_read(struct lttng_ust_ring_buffer *buf,
 119                                          struct lttng_ust_shm_handle *handle)
 120         __attribute__((visibility("hidden")));
 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 void lib_ringbuffer_signal_init(void)
 127         __attribute__((visibility("hidden")));
 128
 129 /*
 130  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 131  */
 132 extern int lib_ring_buffer_snapshot(struct lttng_ust_ring_buffer *buf,
 133                                     unsigned long *consumed,
 134                                     unsigned long *produced,
 135                                     struct lttng_ust_shm_handle *handle)
 136         __attribute__((visibility("hidden")));
 137
 138 extern int lib_ring_buffer_snapshot_sample_positions(
 139                                     struct lttng_ust_ring_buffer *buf,
 140                                     unsigned long *consumed,
 141                                     unsigned long *produced,
 142                                     struct lttng_ust_shm_handle *handle)
 143         __attribute__((visibility("hidden")));
 144
 145 extern void lib_ring_buffer_move_consumer(struct lttng_ust_ring_buffer *buf,
 146                                           unsigned long consumed_new,
 147                                           struct lttng_ust_shm_handle *handle)
 148         __attribute__((visibility("hidden")));
 149
 150 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_ring_buffer *buf,
 151                                       unsigned long consumed,
 152                                       struct lttng_ust_shm_handle *handle)
 153         __attribute__((visibility("hidden")));
 154
 155 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_ring_buffer *buf,
 156                                        struct lttng_ust_shm_handle *handle)
 157         __attribute__((visibility("hidden")));
 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_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_ring_buffer *buf,
 178                                      struct lttng_ust_shm_handle *handle)
 179 {
 180         struct lttng_ust_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 extern void channel_reset(struct lttng_ust_ring_buffer_channel *chan)
 191         __attribute__((visibility("hidden")));
 192
 193 extern void lib_ring_buffer_reset(struct lttng_ust_ring_buffer *buf,
 194                                   struct lttng_ust_shm_handle *handle)
 195         __attribute__((visibility("hidden")));
 196
 197 static inline
 198 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_ring_buffer_config *config,
 199                                          struct lttng_ust_ring_buffer *buf)
 200 {
 201         return v_read(config, &buf->offset);
 202 }
 203
 204 static inline
 205 unsigned long lib_ring_buffer_get_consumed(
 206                 const struct lttng_ust_ring_buffer_config *config __attribute__((unused)),
 207                 struct lttng_ust_ring_buffer *buf)
 208 {
 209         return uatomic_read(&buf->consumed);
 210 }
 211
 212 /*
 213  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 214  * ordering enforced with respect to trace teardown).
 215  */
 216 static inline
 217 int lib_ring_buffer_is_finalized(
 218                 const struct lttng_ust_ring_buffer_config *config __attribute__((unused)),
 219                  struct lttng_ust_ring_buffer *buf)
 220 {
 221         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 222         /*
 223          * Read finalized before counters.
 224          */
 225         cmm_smp_rmb();
 226         return finalized;
 227 }
 228
 229 static inline
 230 int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_ring_buffer_channel *chan)
 231 {
 232         return chan->finalized;
 233 }
 234
 235 static inline
 236 int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_ring_buffer_channel *chan)
 237 {
 238         return uatomic_read(&chan->record_disabled);
 239 }
 240
 241 static inline
 242 unsigned long lib_ring_buffer_get_read_data_size(
 243                                 const struct lttng_ust_ring_buffer_config *config,
 244                                 struct lttng_ust_ring_buffer *buf,
 245                                 struct lttng_ust_shm_handle *handle)
 246 {
 247         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 248 }
 249
 250 static inline
 251 unsigned long lib_ring_buffer_get_records_count(
 252                                 const struct lttng_ust_ring_buffer_config *config,
 253                                 struct lttng_ust_ring_buffer *buf)
 254 {
 255         return v_read(config, &buf->records_count);
 256 }
 257
 258 static inline
 259 unsigned long lib_ring_buffer_get_records_overrun(
 260                                 const struct lttng_ust_ring_buffer_config *config,
 261                                 struct lttng_ust_ring_buffer *buf)
 262 {
 263         return v_read(config, &buf->records_overrun);
 264 }
 265
 266 static inline
 267 unsigned long lib_ring_buffer_get_records_lost_full(
 268                                 const struct lttng_ust_ring_buffer_config *config,
 269                                 struct lttng_ust_ring_buffer *buf)
 270 {
 271         return v_read(config, &buf->records_lost_full);
 272 }
 273
 274 static inline
 275 unsigned long lib_ring_buffer_get_records_lost_wrap(
 276                                 const struct lttng_ust_ring_buffer_config *config,
 277                                 struct lttng_ust_ring_buffer *buf)
 278 {
 279         return v_read(config, &buf->records_lost_wrap);
 280 }
 281
 282 static inline
 283 unsigned long lib_ring_buffer_get_records_lost_big(
 284                                 const struct lttng_ust_ring_buffer_config *config,
 285                                 struct lttng_ust_ring_buffer *buf)
 286 {
 287         return v_read(config, &buf->records_lost_big);
 288 }
 289
 290 static inline
 291 unsigned long lib_ring_buffer_get_records_read(
 292                                 const struct lttng_ust_ring_buffer_config *config,
 293                                 struct lttng_ust_ring_buffer *buf)
 294 {
 295         return v_read(config, &buf->backend.records_read);
 296 }
 297
 298 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */