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 void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 135                                           unsigned long consumed_new,
 136                                           struct lttng_ust_shm_handle *handle);
 137
 138 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 139                                       unsigned long consumed,
 140                                       struct lttng_ust_shm_handle *handle);
 141 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 142                                        struct lttng_ust_shm_handle *handle);
 143
 144 /*
 145  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 146  * to read sub-buffers sequentially.
 147  */
 148 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 149                                                   struct lttng_ust_shm_handle *handle)
 150 {
 151         int ret;
 152
 153         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 154                                        &buf->prod_snapshot, handle);
 155         if (ret)
 156                 return ret;
 157         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 158         return ret;
 159 }
 160
 161 static inline
 162 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 163                                      struct lttng_ust_shm_handle *handle)
 164 {
 165         struct channel *chan;
 166
 167         chan = shmp(handle, buf->backend.chan);
 168         if (!chan)
 169                 return;
 170         lib_ring_buffer_put_subbuf(buf, handle);
 171         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan),
 172                         handle);
 173 }
 174
 175 extern void channel_reset(struct channel *chan);
 176 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 177                                   struct lttng_ust_shm_handle *handle);
 178
 179 static inline
 180 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 181                                          struct lttng_ust_lib_ring_buffer *buf)
 182 {
 183         return v_read(config, &buf->offset);
 184 }
 185
 186 static inline
 187 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 188                                            struct lttng_ust_lib_ring_buffer *buf)
 189 {
 190         return uatomic_read(&buf->consumed);
 191 }
 192
 193 /*
 194  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 195  * ordering enforced with respect to trace teardown).
 196  */
 197 static inline
 198 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 199                                  struct lttng_ust_lib_ring_buffer *buf)
 200 {
 201         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 202         /*
 203          * Read finalized before counters.
 204          */
 205         cmm_smp_rmb();
 206         return finalized;
 207 }
 208
 209 static inline
 210 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 211 {
 212         return chan->finalized;
 213 }
 214
 215 static inline
 216 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 217 {
 218         return uatomic_read(&chan->record_disabled);
 219 }
 220
 221 static inline
 222 unsigned long lib_ring_buffer_get_read_data_size(
 223                                 const struct lttng_ust_lib_ring_buffer_config *config,
 224                                 struct lttng_ust_lib_ring_buffer *buf,
 225                                 struct lttng_ust_shm_handle *handle)
 226 {
 227         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 228 }
 229
 230 static inline
 231 unsigned long lib_ring_buffer_get_records_count(
 232                                 const struct lttng_ust_lib_ring_buffer_config *config,
 233                                 struct lttng_ust_lib_ring_buffer *buf)
 234 {
 235         return v_read(config, &buf->records_count);
 236 }
 237
 238 static inline
 239 unsigned long lib_ring_buffer_get_records_overrun(
 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_overrun);
 244 }
 245
 246 static inline
 247 unsigned long lib_ring_buffer_get_records_lost_full(
 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_lost_full);
 252 }
 253
 254 static inline
 255 unsigned long lib_ring_buffer_get_records_lost_wrap(
 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_wrap);
 260 }
 261
 262 static inline
 263 unsigned long lib_ring_buffer_get_records_lost_big(
 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_big);
 268 }
 269
 270 static inline
 271 unsigned long lib_ring_buffer_get_records_read(
 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->backend.records_read);
 276 }
 277
 278 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */