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