libringbuffer/frontend.h

   1 #ifndef _LTTNG_RING_BUFFER_FRONTEND_H
   2 #define _LTTNG_RING_BUFFER_FRONTEND_H
   3
   4 /*
   5  * libringbuffer/frontend.h
   6  *
   7  * Ring Buffer Library Synchronization Header (API).
   8  *
   9  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; only
  14  * version 2.1 of the License.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  24  *
  25  *
  26  * Author:
  27  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  28  *
  29  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  30  */
  31
  32 #include <urcu/compiler.h>
  33 #include <urcu/uatomic.h>
  34
  35 #include "smp.h"
  36 /* Internal helpers */
  37 #include "frontend_internal.h"
  38
  39 /* Buffer creation/removal and setup operations */
  40
  41 /*
  42  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  43  * padding to let readers get those sub-buffers.  Used for live streaming.
  44  *
  45  * read_timer_interval is the time interval (in us) to wake up pending readers.
  46  *
  47  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  48  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  49  * be set to NULL for other backends.
  50  *
  51  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  52  * memory area for client-specific data. This memory is managed by lib
  53  * ring buffer. priv_data_align is the alignment required for the
  54  * private data area.
  55  */
  56
  57 extern
  58 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  59                                 const char *name,
  60                                 void **priv_data,
  61                                 size_t priv_data_align,
  62                                 size_t priv_data_size,
  63                                 void *priv_data_init,
  64                                 void *buf_addr,
  65                                 size_t subbuf_size, size_t num_subbuf,
  66                                 unsigned int switch_timer_interval,
  67                                 unsigned int read_timer_interval,
  68                                 const int *stream_fds, int nr_stream_fds);
  69
  70 /*
  71  * channel_destroy finalizes all channel's buffers, waits for readers to
  72  * release all references, and destroys the channel.
  73  */
  74 extern
  75 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  76                 int consumer);
  77
  78
  79 /* Buffer read operations */
  80
  81 /*
  82  * Iteration on channel cpumask needs to issue a read barrier to match the write
  83  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  84  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  85  * only performed at channel destruction.
  86  */
  87 #define for_each_channel_cpu(cpu, chan)                                 \
  88         for_each_possible_cpu(cpu)
  89
  90 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  91                                 const struct lttng_ust_lib_ring_buffer_config *config,
  92                                 struct channel *chan, int cpu,
  93                                 struct lttng_ust_shm_handle *handle,
  94                                 int *shm_fd, int *wait_fd,
  95                                 int *wakeup_fd,
  96                                 uint64_t *memory_map_size);
  97 extern
  98 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  99                         struct channel *chan,
 100                         struct lttng_ust_shm_handle *handle);
 101 extern
 102 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 103                         struct channel *chan,
 104                         struct lttng_ust_shm_handle *handle);
 105 extern
 106 int ring_buffer_stream_close_wait_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 extern
 111 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 112                 struct channel *chan,
 113                 struct lttng_ust_shm_handle *handle,
 114                 int cpu);
 115
 116 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 117                                      struct lttng_ust_shm_handle *handle);
 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 void lib_ringbuffer_signal_init(void);
 126
 127 /*
 128  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 129  */
 130 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 131                                     unsigned long *consumed,
 132                                     unsigned long *produced,
 133                                     struct lttng_ust_shm_handle *handle);
 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 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 140                                           unsigned long consumed_new,
 141                                           struct lttng_ust_shm_handle *handle);
 142
 143 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 144                                       unsigned long consumed,
 145                                       struct lttng_ust_shm_handle *handle);
 146 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 147                                        struct lttng_ust_shm_handle *handle);
 148
 149 /*
 150  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 151  * to read sub-buffers sequentially.
 152  */
 153 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 154                                                   struct lttng_ust_shm_handle *handle)
 155 {
 156         int ret;
 157
 158         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 159                                        &buf->prod_snapshot, handle);
 160         if (ret)
 161                 return ret;
 162         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 163         return ret;
 164 }
 165
 166 static inline
 167 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 168                                      struct lttng_ust_shm_handle *handle)
 169 {
 170         struct channel *chan;
 171
 172         chan = shmp(handle, buf->backend.chan);
 173         if (!chan)
 174                 return;
 175         lib_ring_buffer_put_subbuf(buf, handle);
 176         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 177                         handle);
 178 }
 179
 180 extern void channel_reset(struct channel *chan);
 181 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 182                                   struct lttng_ust_shm_handle *handle);
 183
 184 static inline
 185 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 186                                          struct lttng_ust_lib_ring_buffer *buf)
 187 {
 188         return v_read(config, &buf->offset);
 189 }
 190
 191 static inline
 192 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 193                                            struct lttng_ust_lib_ring_buffer *buf)
 194 {
 195         return uatomic_read(&buf->consumed);
 196 }
 197
 198 /*
 199  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 200  * ordering enforced with respect to trace teardown).
 201  */
 202 static inline
 203 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 204                                  struct lttng_ust_lib_ring_buffer *buf)
 205 {
 206         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 207         /*
 208          * Read finalized before counters.
 209          */
 210         cmm_smp_rmb();
 211         return finalized;
 212 }
 213
 214 static inline
 215 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 216 {
 217         return chan->finalized;
 218 }
 219
 220 static inline
 221 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 222 {
 223         return uatomic_read(&chan->record_disabled);
 224 }
 225
 226 static inline
 227 unsigned long lib_ring_buffer_get_read_data_size(
 228                                 const struct lttng_ust_lib_ring_buffer_config *config,
 229                                 struct lttng_ust_lib_ring_buffer *buf,
 230                                 struct lttng_ust_shm_handle *handle)
 231 {
 232         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 233 }
 234
 235 static inline
 236 unsigned long lib_ring_buffer_get_records_count(
 237                                 const struct lttng_ust_lib_ring_buffer_config *config,
 238                                 struct lttng_ust_lib_ring_buffer *buf)
 239 {
 240         return v_read(config, &buf->records_count);
 241 }
 242
 243 static inline
 244 unsigned long lib_ring_buffer_get_records_overrun(
 245                                 const struct lttng_ust_lib_ring_buffer_config *config,
 246                                 struct lttng_ust_lib_ring_buffer *buf)
 247 {
 248         return v_read(config, &buf->records_overrun);
 249 }
 250
 251 static inline
 252 unsigned long lib_ring_buffer_get_records_lost_full(
 253                                 const struct lttng_ust_lib_ring_buffer_config *config,
 254                                 struct lttng_ust_lib_ring_buffer *buf)
 255 {
 256         return v_read(config, &buf->records_lost_full);
 257 }
 258
 259 static inline
 260 unsigned long lib_ring_buffer_get_records_lost_wrap(
 261                                 const struct lttng_ust_lib_ring_buffer_config *config,
 262                                 struct lttng_ust_lib_ring_buffer *buf)
 263 {
 264         return v_read(config, &buf->records_lost_wrap);
 265 }
 266
 267 static inline
 268 unsigned long lib_ring_buffer_get_records_lost_big(
 269                                 const struct lttng_ust_lib_ring_buffer_config *config,
 270                                 struct lttng_ust_lib_ring_buffer *buf)
 271 {
 272         return v_read(config, &buf->records_lost_big);
 273 }
 274
 275 static inline
 276 unsigned long lib_ring_buffer_get_records_read(
 277                                 const struct lttng_ust_lib_ring_buffer_config *config,
 278                                 struct lttng_ust_lib_ring_buffer *buf)
 279 {
 280         return v_read(config, &buf->backend.records_read);
 281 }
 282
 283 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */