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                                 int64_t blocking_timeout);
  70
  71 /*
  72  * channel_destroy finalizes all channel's buffers, waits for readers to
  73  * release all references, and destroys the channel.
  74  */
  75 extern
  76 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  77                 int consumer);
  78
  79
  80 /* Buffer read operations */
  81
  82 /*
  83  * Iteration on channel cpumask needs to issue a read barrier to match the write
  84  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  85  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  86  * only performed at channel destruction.
  87  */
  88 #define for_each_channel_cpu(cpu, chan)                                 \
  89         for_each_possible_cpu(cpu)
  90
  91 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  92                                 const struct lttng_ust_lib_ring_buffer_config *config,
  93                                 struct channel *chan, int cpu,
  94                                 struct lttng_ust_shm_handle *handle,
  95                                 int *shm_fd, int *wait_fd,
  96                                 int *wakeup_fd,
  97                                 uint64_t *memory_map_size);
  98 extern
  99 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 100                         struct channel *chan,
 101                         struct lttng_ust_shm_handle *handle);
 102 extern
 103 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 104                         struct channel *chan,
 105                         struct lttng_ust_shm_handle *handle);
 106 extern
 107 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 108                 struct channel *chan,
 109                 struct lttng_ust_shm_handle *handle,
 110                 int cpu);
 111 extern
 112 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 113                 struct channel *chan,
 114                 struct lttng_ust_shm_handle *handle,
 115                 int cpu);
 116
 117 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 118                                      struct lttng_ust_shm_handle *handle);
 119 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 120                                          struct lttng_ust_shm_handle *handle);
 121
 122 /*
 123  * Initialize signals for ring buffer. Should be called early e.g. by
 124  * main() in the program to affect all threads.
 125  */
 126 void lib_ringbuffer_signal_init(void);
 127
 128 /*
 129  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 130  */
 131 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 132                                     unsigned long *consumed,
 133                                     unsigned long *produced,
 134                                     struct lttng_ust_shm_handle *handle);
 135 extern int lib_ring_buffer_snapshot_sample_positions(
 136                                     struct lttng_ust_lib_ring_buffer *buf,
 137                                     unsigned long *consumed,
 138                                     unsigned long *produced,
 139                                     struct lttng_ust_shm_handle *handle);
 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 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 145                                       unsigned long consumed,
 146                                       struct lttng_ust_shm_handle *handle);
 147 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 148                                        struct lttng_ust_shm_handle *handle);
 149
 150 /*
 151  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 152  * to read sub-buffers sequentially.
 153  */
 154 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 155                                                   struct lttng_ust_shm_handle *handle)
 156 {
 157         int ret;
 158
 159         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 160                                        &buf->prod_snapshot, handle);
 161         if (ret)
 162                 return ret;
 163         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 164         return ret;
 165 }
 166
 167 static inline
 168 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 169                                      struct lttng_ust_shm_handle *handle)
 170 {
 171         struct channel *chan;
 172
 173         chan = shmp(handle, buf->backend.chan);
 174         if (!chan)
 175                 return;
 176         lib_ring_buffer_put_subbuf(buf, handle);
 177         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 178                         handle);
 179 }
 180
 181 extern void channel_reset(struct channel *chan);
 182 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 183                                   struct lttng_ust_shm_handle *handle);
 184
 185 static inline
 186 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 187                                          struct lttng_ust_lib_ring_buffer *buf)
 188 {
 189         return v_read(config, &buf->offset);
 190 }
 191
 192 static inline
 193 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 194                                            struct lttng_ust_lib_ring_buffer *buf)
 195 {
 196         return uatomic_read(&buf->consumed);
 197 }
 198
 199 /*
 200  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 201  * ordering enforced with respect to trace teardown).
 202  */
 203 static inline
 204 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 205                                  struct lttng_ust_lib_ring_buffer *buf)
 206 {
 207         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 208         /*
 209          * Read finalized before counters.
 210          */
 211         cmm_smp_rmb();
 212         return finalized;
 213 }
 214
 215 static inline
 216 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 217 {
 218         return chan->finalized;
 219 }
 220
 221 static inline
 222 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 223 {
 224         return uatomic_read(&chan->record_disabled);
 225 }
 226
 227 static inline
 228 unsigned long lib_ring_buffer_get_read_data_size(
 229                                 const struct lttng_ust_lib_ring_buffer_config *config,
 230                                 struct lttng_ust_lib_ring_buffer *buf,
 231                                 struct lttng_ust_shm_handle *handle)
 232 {
 233         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 234 }
 235
 236 static inline
 237 unsigned long lib_ring_buffer_get_records_count(
 238                                 const struct lttng_ust_lib_ring_buffer_config *config,
 239                                 struct lttng_ust_lib_ring_buffer *buf)
 240 {
 241         return v_read(config, &buf->records_count);
 242 }
 243
 244 static inline
 245 unsigned long lib_ring_buffer_get_records_overrun(
 246                                 const struct lttng_ust_lib_ring_buffer_config *config,
 247                                 struct lttng_ust_lib_ring_buffer *buf)
 248 {
 249         return v_read(config, &buf->records_overrun);
 250 }
 251
 252 static inline
 253 unsigned long lib_ring_buffer_get_records_lost_full(
 254                                 const struct lttng_ust_lib_ring_buffer_config *config,
 255                                 struct lttng_ust_lib_ring_buffer *buf)
 256 {
 257         return v_read(config, &buf->records_lost_full);
 258 }
 259
 260 static inline
 261 unsigned long lib_ring_buffer_get_records_lost_wrap(
 262                                 const struct lttng_ust_lib_ring_buffer_config *config,
 263                                 struct lttng_ust_lib_ring_buffer *buf)
 264 {
 265         return v_read(config, &buf->records_lost_wrap);
 266 }
 267
 268 static inline
 269 unsigned long lib_ring_buffer_get_records_lost_big(
 270                                 const struct lttng_ust_lib_ring_buffer_config *config,
 271                                 struct lttng_ust_lib_ring_buffer *buf)
 272 {
 273         return v_read(config, &buf->records_lost_big);
 274 }
 275
 276 static inline
 277 unsigned long lib_ring_buffer_get_records_read(
 278                                 const struct lttng_ust_lib_ring_buffer_config *config,
 279                                 struct lttng_ust_lib_ring_buffer *buf)
 280 {
 281         return v_read(config, &buf->backend.records_read);
 282 }
 283
 284 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */