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 /* Internal helpers */
  22 #include "frontend_internal.h"
  23
  24 /* Buffer creation/removal and setup operations */
  25
  26 /*
  27  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  28  * padding to let readers get those sub-buffers.  Used for live streaming.
  29  *
  30  * read_timer_interval is the time interval (in us) to wake up pending readers.
  31  *
  32  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  33  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  34  * be set to NULL for other backends.
  35  *
  36  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  37  * memory area for client-specific data. This memory is managed by lib
  38  * ring buffer. priv_data_align is the alignment required for the
  39  * 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                                 void **priv_data,
  46                                 size_t priv_data_align,
  47                                 size_t priv_data_size,
  48                                 void *priv_data_init,
  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
  56 /*
  57  * channel_destroy finalizes all channel's buffers, waits for readers to
  58  * release all references, and destroys the channel.
  59  */
  60 extern
  61 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  62                 int consumer);
  63
  64
  65 /* Buffer read operations */
  66
  67 /*
  68  * Iteration on channel cpumask needs to issue a read barrier to match the write
  69  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  70  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  71  * only performed at channel destruction.
  72  */
  73 #define for_each_channel_cpu(cpu, chan)                                 \
  74         for_each_possible_cpu(cpu)
  75
  76 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  77                                 const struct lttng_ust_lib_ring_buffer_config *config,
  78                                 struct channel *chan, int cpu,
  79                                 struct lttng_ust_shm_handle *handle,
  80                                 int *shm_fd, int *wait_fd,
  81                                 int *wakeup_fd,
  82                                 uint64_t *memory_map_size);
  83 extern
  84 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  85                         struct channel *chan,
  86                         struct lttng_ust_shm_handle *handle);
  87 extern
  88 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  89                         struct channel *chan,
  90                         struct lttng_ust_shm_handle *handle);
  91 extern
  92 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  93                 struct channel *chan,
  94                 struct lttng_ust_shm_handle *handle,
  95                 int cpu);
  96 extern
  97 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  98                 struct channel *chan,
  99                 struct lttng_ust_shm_handle *handle,
 100                 int cpu);
 101
 102 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 103                                      struct lttng_ust_shm_handle *handle);
 104 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 105                                          struct lttng_ust_shm_handle *handle);
 106
 107 /*
 108  * Initialize signals for ring buffer. Should be called early e.g. by
 109  * main() in the program to affect all threads.
 110  */
 111 void lib_ringbuffer_signal_init(void);
 112
 113 /*
 114  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 115  */
 116 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 117                                     unsigned long *consumed,
 118                                     unsigned long *produced,
 119                                     struct lttng_ust_shm_handle *handle);
 120 extern int lib_ring_buffer_snapshot_sample_positions(
 121                                     struct lttng_ust_lib_ring_buffer *buf,
 122                                     unsigned long *consumed,
 123                                     unsigned long *produced,
 124                                     struct lttng_ust_shm_handle *handle);
 125 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 126                                           unsigned long consumed_new,
 127                                           struct lttng_ust_shm_handle *handle);
 128
 129 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 130                                       unsigned long consumed,
 131                                       struct lttng_ust_shm_handle *handle);
 132 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 133                                        struct lttng_ust_shm_handle *handle);
 134
 135 /*
 136  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 137  * to read sub-buffers sequentially.
 138  */
 139 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 140                                                   struct lttng_ust_shm_handle *handle)
 141 {
 142         int ret;
 143
 144         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 145                                        &buf->prod_snapshot, handle);
 146         if (ret)
 147                 return ret;
 148         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 149         return ret;
 150 }
 151
 152 static inline
 153 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 154                                      struct lttng_ust_shm_handle *handle)
 155 {
 156         struct channel *chan;
 157
 158         chan = shmp(handle, buf->backend.chan);
 159         if (!chan)
 160                 return;
 161         lib_ring_buffer_put_subbuf(buf, handle);
 162         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 163                         handle);
 164 }
 165
 166 extern void channel_reset(struct channel *chan);
 167 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 168                                   struct lttng_ust_shm_handle *handle);
 169
 170 static inline
 171 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 172                                          struct lttng_ust_lib_ring_buffer *buf)
 173 {
 174         return v_read(config, &buf->offset);
 175 }
 176
 177 static inline
 178 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 179                                            struct lttng_ust_lib_ring_buffer *buf)
 180 {
 181         return uatomic_read(&buf->consumed);
 182 }
 183
 184 /*
 185  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 186  * ordering enforced with respect to trace teardown).
 187  */
 188 static inline
 189 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 190                                  struct lttng_ust_lib_ring_buffer *buf)
 191 {
 192         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 193         /*
 194          * Read finalized before counters.
 195          */
 196         cmm_smp_rmb();
 197         return finalized;
 198 }
 199
 200 static inline
 201 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 202 {
 203         return chan->finalized;
 204 }
 205
 206 static inline
 207 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 208 {
 209         return uatomic_read(&chan->record_disabled);
 210 }
 211
 212 static inline
 213 unsigned long lib_ring_buffer_get_read_data_size(
 214                                 const struct lttng_ust_lib_ring_buffer_config *config,
 215                                 struct lttng_ust_lib_ring_buffer *buf,
 216                                 struct lttng_ust_shm_handle *handle)
 217 {
 218         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 219 }
 220
 221 static inline
 222 unsigned long lib_ring_buffer_get_records_count(
 223                                 const struct lttng_ust_lib_ring_buffer_config *config,
 224                                 struct lttng_ust_lib_ring_buffer *buf)
 225 {
 226         return v_read(config, &buf->records_count);
 227 }
 228
 229 static inline
 230 unsigned long lib_ring_buffer_get_records_overrun(
 231                                 const struct lttng_ust_lib_ring_buffer_config *config,
 232                                 struct lttng_ust_lib_ring_buffer *buf)
 233 {
 234         return v_read(config, &buf->records_overrun);
 235 }
 236
 237 static inline
 238 unsigned long lib_ring_buffer_get_records_lost_full(
 239                                 const struct lttng_ust_lib_ring_buffer_config *config,
 240                                 struct lttng_ust_lib_ring_buffer *buf)
 241 {
 242         return v_read(config, &buf->records_lost_full);
 243 }
 244
 245 static inline
 246 unsigned long lib_ring_buffer_get_records_lost_wrap(
 247                                 const struct lttng_ust_lib_ring_buffer_config *config,
 248                                 struct lttng_ust_lib_ring_buffer *buf)
 249 {
 250         return v_read(config, &buf->records_lost_wrap);
 251 }
 252
 253 static inline
 254 unsigned long lib_ring_buffer_get_records_lost_big(
 255                                 const struct lttng_ust_lib_ring_buffer_config *config,
 256                                 struct lttng_ust_lib_ring_buffer *buf)
 257 {
 258         return v_read(config, &buf->records_lost_big);
 259 }
 260
 261 static inline
 262 unsigned long lib_ring_buffer_get_records_read(
 263                                 const struct lttng_ust_lib_ring_buffer_config *config,
 264                                 struct lttng_ust_lib_ring_buffer *buf)
 265 {
 266         return v_read(config, &buf->backend.records_read);
 267 }
 268
 269 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */