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
  33 #include <urcu/compiler.h>
  34 #include <urcu/uatomic.h>
  35
  36 #include "smp.h"
  37 /* Internal helpers */
  38 #include "frontend_internal.h"
  39
  40 /* Buffer creation/removal and setup operations */
  41
  42 /*
  43  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  44  * padding to let readers get those sub-buffers.  Used for live streaming.
  45  *
  46  * read_timer_interval is the time interval (in us) to wake up pending readers.
  47  *
  48  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  49  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  50  * be set to NULL for other backends.
  51  *
  52  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  53  * memory area for client-specific data. This memory is managed by lib
  54  * ring buffer. priv_data_align is the alignment required for the
  55  * private data area.
  56  */
  57
  58 extern
  59 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  60                                 const char *name,
  61                                 void **priv_data,
  62                                 size_t priv_data_align,
  63                                 size_t priv_data_size,
  64                                 void *priv_data_init,
  65                                 void *buf_addr,
  66                                 size_t subbuf_size, size_t num_subbuf,
  67                                 unsigned int switch_timer_interval,
  68                                 unsigned int read_timer_interval,
  69                                 const int *stream_fds, int nr_stream_fds,
  70                                 int64_t blocking_timeout);
  71
  72 /*
  73  * channel_destroy finalizes all channel's buffers, waits for readers to
  74  * release all references, and destroys the channel.
  75  */
  76 extern
  77 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  78                 int consumer);
  79
  80
  81 /* Buffer read operations */
  82
  83 /*
  84  * Iteration on channel cpumask needs to issue a read barrier to match the write
  85  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  86  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  87  * only performed at channel destruction.
  88  */
  89 #define for_each_channel_cpu(cpu, chan)                                 \
  90         for_each_possible_cpu(cpu)
  91
  92 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  93                                 const struct lttng_ust_lib_ring_buffer_config *config,
  94                                 struct channel *chan, int cpu,
  95                                 struct lttng_ust_shm_handle *handle,
  96                                 int *shm_fd, int *wait_fd,
  97                                 int *wakeup_fd,
  98                                 uint64_t *memory_map_size);
  99 extern
 100 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 101                         struct channel *chan,
 102                         struct lttng_ust_shm_handle *handle);
 103 extern
 104 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 105                         struct channel *chan,
 106                         struct lttng_ust_shm_handle *handle);
 107 extern
 108 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 109                 struct channel *chan,
 110                 struct lttng_ust_shm_handle *handle,
 111                 int cpu);
 112 extern
 113 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 114                 struct channel *chan,
 115                 struct lttng_ust_shm_handle *handle,
 116                 int cpu);
 117
 118 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 119                                      struct lttng_ust_shm_handle *handle);
 120 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 121                                          struct lttng_ust_shm_handle *handle);
 122
 123 /*
 124  * Initialize signals for ring buffer. Should be called early e.g. by
 125  * main() in the program to affect all threads.
 126  */
 127 void lib_ringbuffer_signal_init(void);
 128
 129 /*
 130  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 131  */
 132 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 133                                     unsigned long *consumed,
 134                                     unsigned long *produced,
 135                                     struct lttng_ust_shm_handle *handle);
 136 extern int lib_ring_buffer_snapshot_sample_positions(
 137                                     struct lttng_ust_lib_ring_buffer *buf,
 138                                     unsigned long *consumed,
 139                                     unsigned long *produced,
 140                                     struct lttng_ust_shm_handle *handle);
 141 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 142                                           unsigned long consumed_new,
 143                                           struct lttng_ust_shm_handle *handle);
 144
 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 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 149                                        struct lttng_ust_shm_handle *handle);
 150
 151 /*
 152  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 153  * to read sub-buffers sequentially.
 154  */
 155 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 156                                                   struct lttng_ust_shm_handle *handle)
 157 {
 158         int ret;
 159
 160         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 161                                        &buf->prod_snapshot, handle);
 162         if (ret)
 163                 return ret;
 164         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 165         return ret;
 166 }
 167
 168 static inline
 169 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 170                                      struct lttng_ust_shm_handle *handle)
 171 {
 172         struct channel *chan;
 173
 174         chan = shmp(handle, buf->backend.chan);
 175         if (!chan)
 176                 return;
 177         lib_ring_buffer_put_subbuf(buf, handle);
 178         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 179                         handle);
 180 }
 181
 182 extern void channel_reset(struct channel *chan);
 183 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 184                                   struct lttng_ust_shm_handle *handle);
 185
 186 static inline
 187 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 188                                          struct lttng_ust_lib_ring_buffer *buf)
 189 {
 190         return v_read(config, &buf->offset);
 191 }
 192
 193 static inline
 194 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 195                                            struct lttng_ust_lib_ring_buffer *buf)
 196 {
 197         return uatomic_read(&buf->consumed);
 198 }
 199
 200 /*
 201  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 202  * ordering enforced with respect to trace teardown).
 203  */
 204 static inline
 205 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 206                                  struct lttng_ust_lib_ring_buffer *buf)
 207 {
 208         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 209         /*
 210          * Read finalized before counters.
 211          */
 212         cmm_smp_rmb();
 213         return finalized;
 214 }
 215
 216 static inline
 217 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 218 {
 219         return chan->finalized;
 220 }
 221
 222 static inline
 223 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 224 {
 225         return uatomic_read(&chan->record_disabled);
 226 }
 227
 228 static inline
 229 unsigned long lib_ring_buffer_get_read_data_size(
 230                                 const struct lttng_ust_lib_ring_buffer_config *config,
 231                                 struct lttng_ust_lib_ring_buffer *buf,
 232                                 struct lttng_ust_shm_handle *handle)
 233 {
 234         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 235 }
 236
 237 static inline
 238 unsigned long lib_ring_buffer_get_records_count(
 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_count);
 243 }
 244
 245 static inline
 246 unsigned long lib_ring_buffer_get_records_overrun(
 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_overrun);
 251 }
 252
 253 static inline
 254 unsigned long lib_ring_buffer_get_records_lost_full(
 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_full);
 259 }
 260
 261 static inline
 262 unsigned long lib_ring_buffer_get_records_lost_wrap(
 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->records_lost_wrap);
 267 }
 268
 269 static inline
 270 unsigned long lib_ring_buffer_get_records_lost_big(
 271                                 const struct lttng_ust_lib_ring_buffer_config *config,
 272                                 struct lttng_ust_lib_ring_buffer *buf)
 273 {
 274         return v_read(config, &buf->records_lost_big);
 275 }
 276
 277 static inline
 278 unsigned long lib_ring_buffer_get_records_read(
 279                                 const struct lttng_ust_lib_ring_buffer_config *config,
 280                                 struct lttng_ust_lib_ring_buffer *buf)
 281 {
 282         return v_read(config, &buf->backend.records_read);
 283 }
 284
 285 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */