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 #include "ust-helper.h"
  22
  23 /* Internal helpers */
  24 #include "frontend_internal.h"
  25
  26 /* Buffer creation/removal and setup operations */
  27
  28 /*
  29  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  30  * padding to let readers get those sub-buffers.  Used for live streaming.
  31  *
  32  * read_timer_interval is the time interval (in us) to wake up pending readers.
  33  *
  34  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  35  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  36  * be set to NULL for other backends.
  37  *
  38  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  39  * memory area for client-specific data. This memory is managed by lib
  40  * ring buffer. priv_data_align is the alignment required for the
  41  * private data area.
  42  */
  43
  44 LTTNG_HIDDEN
  45 extern
  46 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  47                                 const char *name,
  48                                 void **priv_data,
  49                                 size_t priv_data_align,
  50                                 size_t priv_data_size,
  51                                 void *priv_data_init,
  52                                 void *buf_addr,
  53                                 size_t subbuf_size, size_t num_subbuf,
  54                                 unsigned int switch_timer_interval,
  55                                 unsigned int read_timer_interval,
  56                                 const int *stream_fds, int nr_stream_fds,
  57                                 int64_t blocking_timeout);
  58
  59 /*
  60  * channel_destroy finalizes all channel's buffers, waits for readers to
  61  * release all references, and destroys the channel.
  62  */
  63 LTTNG_HIDDEN
  64 extern
  65 void channel_destroy(struct channel *chan, 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 LTTNG_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 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 LTTNG_HIDDEN
  89 extern
  90 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  91                         struct channel *chan,
  92                         struct lttng_ust_shm_handle *handle);
  93 LTTNG_HIDDEN
  94 extern
  95 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  96                         struct channel *chan,
  97                         struct lttng_ust_shm_handle *handle);
  98 LTTNG_HIDDEN
  99 extern
 100 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 101                 struct channel *chan,
 102                 struct lttng_ust_shm_handle *handle,
 103                 int cpu);
 104 LTTNG_HIDDEN
 105 extern
 106 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 107                 struct channel *chan,
 108                 struct lttng_ust_shm_handle *handle,
 109                 int cpu);
 110
 111 LTTNG_HIDDEN
 112 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 113                                      struct lttng_ust_shm_handle *handle);
 114 LTTNG_HIDDEN
 115 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 116                                          struct lttng_ust_shm_handle *handle);
 117
 118 /*
 119  * Initialize signals for ring buffer. Should be called early e.g. by
 120  * main() in the program to affect all threads.
 121  */
 122 LTTNG_HIDDEN
 123 void lib_ringbuffer_signal_init(void);
 124
 125 /*
 126  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 127  */
 128 LTTNG_HIDDEN
 129 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 130                                     unsigned long *consumed,
 131                                     unsigned long *produced,
 132                                     struct lttng_ust_shm_handle *handle);
 133 LTTNG_HIDDEN
 134 extern int lib_ring_buffer_snapshot_sample_positions(
 135                                     struct lttng_ust_lib_ring_buffer *buf,
 136                                     unsigned long *consumed,
 137                                     unsigned long *produced,
 138                                     struct lttng_ust_shm_handle *handle);
 139 LTTNG_HIDDEN
 140 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 141                                           unsigned long consumed_new,
 142                                           struct lttng_ust_shm_handle *handle);
 143
 144 LTTNG_HIDDEN
 145 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 146                                       unsigned long consumed,
 147                                       struct lttng_ust_shm_handle *handle);
 148 LTTNG_HIDDEN
 149 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 150                                        struct lttng_ust_shm_handle *handle);
 151
 152 /*
 153  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 154  * to read sub-buffers sequentially.
 155  */
 156 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 157                                                   struct lttng_ust_shm_handle *handle)
 158 {
 159         int ret;
 160
 161         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 162                                        &buf->prod_snapshot, handle);
 163         if (ret)
 164                 return ret;
 165         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 166         return ret;
 167 }
 168
 169 static inline
 170 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 171                                      struct lttng_ust_shm_handle *handle)
 172 {
 173         struct channel *chan;
 174
 175         chan = shmp(handle, buf->backend.chan);
 176         if (!chan)
 177                 return;
 178         lib_ring_buffer_put_subbuf(buf, handle);
 179         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 180                         handle);
 181 }
 182
 183 LTTNG_HIDDEN
 184 extern void channel_reset(struct channel *chan);
 185 LTTNG_HIDDEN
 186 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 187                                   struct lttng_ust_shm_handle *handle);
 188
 189 static inline
 190 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 191                                          struct lttng_ust_lib_ring_buffer *buf)
 192 {
 193         return v_read(config, &buf->offset);
 194 }
 195
 196 static inline
 197 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 198                                            struct lttng_ust_lib_ring_buffer *buf)
 199 {
 200         return uatomic_read(&buf->consumed);
 201 }
 202
 203 /*
 204  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 205  * ordering enforced with respect to trace teardown).
 206  */
 207 static inline
 208 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 209                                  struct lttng_ust_lib_ring_buffer *buf)
 210 {
 211         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 212         /*
 213          * Read finalized before counters.
 214          */
 215         cmm_smp_rmb();
 216         return finalized;
 217 }
 218
 219 static inline
 220 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 221 {
 222         return chan->finalized;
 223 }
 224
 225 static inline
 226 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 227 {
 228         return uatomic_read(&chan->record_disabled);
 229 }
 230
 231 static inline
 232 unsigned long lib_ring_buffer_get_read_data_size(
 233                                 const struct lttng_ust_lib_ring_buffer_config *config,
 234                                 struct lttng_ust_lib_ring_buffer *buf,
 235                                 struct lttng_ust_shm_handle *handle)
 236 {
 237         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 238 }
 239
 240 static inline
 241 unsigned long lib_ring_buffer_get_records_count(
 242                                 const struct lttng_ust_lib_ring_buffer_config *config,
 243                                 struct lttng_ust_lib_ring_buffer *buf)
 244 {
 245         return v_read(config, &buf->records_count);
 246 }
 247
 248 static inline
 249 unsigned long lib_ring_buffer_get_records_overrun(
 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_overrun);
 254 }
 255
 256 static inline
 257 unsigned long lib_ring_buffer_get_records_lost_full(
 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_lost_full);
 262 }
 263
 264 static inline
 265 unsigned long lib_ring_buffer_get_records_lost_wrap(
 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_wrap);
 270 }
 271
 272 static inline
 273 unsigned long lib_ring_buffer_get_records_lost_big(
 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_big);
 278 }
 279
 280 static inline
 281 unsigned long lib_ring_buffer_get_records_read(
 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->backend.records_read);
 286 }
 287
 288 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */