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 #include <stddef.h>
  32 #include <stdint.h>
  33
  34 #include <urcu/compiler.h>
  35 #include <urcu/uatomic.h>
  36
  37 #include "smp.h"
  38 /* Internal helpers */
  39 #include "frontend_internal.h"
  40
  41 /* Buffer creation/removal and setup operations */
  42
  43 /*
  44  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  45  * padding to let readers get those sub-buffers.  Used for live streaming.
  46  *
  47  * read_timer_interval is the time interval (in us) to wake up pending readers.
  48  *
  49  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  50  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  51  * be set to NULL for other backends.
  52  *
  53  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  54  * memory area for client-specific data. This memory is managed by lib
  55  * ring buffer. priv_data_align is the alignment required for the
  56  * private data area.
  57  */
  58
  59 extern
  60 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  61                                 const char *name,
  62                                 void **priv_data,
  63                                 size_t priv_data_align,
  64                                 size_t priv_data_size,
  65                                 void *priv_data_init,
  66                                 void *buf_addr,
  67                                 size_t subbuf_size, size_t num_subbuf,
  68                                 unsigned int switch_timer_interval,
  69                                 unsigned int read_timer_interval,
  70                                 const int *stream_fds, int nr_stream_fds,
  71                                 int64_t blocking_timeout);
  72
  73 /*
  74  * channel_destroy finalizes all channel's buffers, waits for readers to
  75  * release all references, and destroys the channel.
  76  */
  77 extern
  78 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  79                 int consumer);
  80
  81
  82 /* Buffer read operations */
  83
  84 /*
  85  * Iteration on channel cpumask needs to issue a read barrier to match the write
  86  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  87  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  88  * only performed at channel destruction.
  89  */
  90 #define for_each_channel_cpu(cpu, chan)                                 \
  91         for_each_possible_cpu(cpu)
  92
  93 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  94                                 const struct lttng_ust_lib_ring_buffer_config *config,
  95                                 struct channel *chan, int cpu,
  96                                 struct lttng_ust_shm_handle *handle,
  97                                 int *shm_fd, int *wait_fd,
  98                                 int *wakeup_fd,
  99                                 uint64_t *memory_map_size);
 100 extern
 101 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 102                         struct channel *chan,
 103                         struct lttng_ust_shm_handle *handle);
 104 extern
 105 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 106                         struct channel *chan,
 107                         struct lttng_ust_shm_handle *handle);
 108 extern
 109 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 110                 struct channel *chan,
 111                 struct lttng_ust_shm_handle *handle,
 112                 int cpu);
 113 extern
 114 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 115                 struct channel *chan,
 116                 struct lttng_ust_shm_handle *handle,
 117                 int cpu);
 118
 119 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 120                                      struct lttng_ust_shm_handle *handle);
 121 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 122                                          struct lttng_ust_shm_handle *handle);
 123
 124 /*
 125  * Initialize signals for ring buffer. Should be called early e.g. by
 126  * main() in the program to affect all threads.
 127  */
 128 void lib_ringbuffer_signal_init(void);
 129
 130 /*
 131  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 132  */
 133 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 134                                     unsigned long *consumed,
 135                                     unsigned long *produced,
 136                                     struct lttng_ust_shm_handle *handle);
 137 extern int lib_ring_buffer_snapshot_sample_positions(
 138                                     struct lttng_ust_lib_ring_buffer *buf,
 139                                     unsigned long *consumed,
 140                                     unsigned long *produced,
 141                                     struct lttng_ust_shm_handle *handle);
 142 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 143                                           unsigned long consumed_new,
 144                                           struct lttng_ust_shm_handle *handle);
 145
 146 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 147                                       unsigned long consumed,
 148                                       struct lttng_ust_shm_handle *handle);
 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 extern void channel_reset(struct channel *chan);
 184 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 185                                   struct lttng_ust_shm_handle *handle);
 186
 187 static inline
 188 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 189                                          struct lttng_ust_lib_ring_buffer *buf)
 190 {
 191         return v_read(config, &buf->offset);
 192 }
 193
 194 static inline
 195 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 196                                            struct lttng_ust_lib_ring_buffer *buf)
 197 {
 198         return uatomic_read(&buf->consumed);
 199 }
 200
 201 /*
 202  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 203  * ordering enforced with respect to trace teardown).
 204  */
 205 static inline
 206 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 207                                  struct lttng_ust_lib_ring_buffer *buf)
 208 {
 209         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 210         /*
 211          * Read finalized before counters.
 212          */
 213         cmm_smp_rmb();
 214         return finalized;
 215 }
 216
 217 static inline
 218 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 219 {
 220         return chan->finalized;
 221 }
 222
 223 static inline
 224 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 225 {
 226         return uatomic_read(&chan->record_disabled);
 227 }
 228
 229 static inline
 230 unsigned long lib_ring_buffer_get_read_data_size(
 231                                 const struct lttng_ust_lib_ring_buffer_config *config,
 232                                 struct lttng_ust_lib_ring_buffer *buf,
 233                                 struct lttng_ust_shm_handle *handle)
 234 {
 235         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 236 }
 237
 238 static inline
 239 unsigned long lib_ring_buffer_get_records_count(
 240                                 const struct lttng_ust_lib_ring_buffer_config *config,
 241                                 struct lttng_ust_lib_ring_buffer *buf)
 242 {
 243         return v_read(config, &buf->records_count);
 244 }
 245
 246 static inline
 247 unsigned long lib_ring_buffer_get_records_overrun(
 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_overrun);
 252 }
 253
 254 static inline
 255 unsigned long lib_ring_buffer_get_records_lost_full(
 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_lost_full);
 260 }
 261
 262 static inline
 263 unsigned long lib_ring_buffer_get_records_lost_wrap(
 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_wrap);
 268 }
 269
 270 static inline
 271 unsigned long lib_ring_buffer_get_records_lost_big(
 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_big);
 276 }
 277
 278 static inline
 279 unsigned long lib_ring_buffer_get_records_read(
 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->backend.records_read);
 284 }
 285
 286 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */