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, char **shm_path,
  69                                 int **wait_fd, char **wait_pipe_path,
  70                                 uint64_t **memory_map_size);
  71
  72 /* channel_handle_create - for consumer. */
  73 extern
  74 struct lttng_ust_shm_handle *channel_handle_create(int shm_fd, int wait_fd,
  75                                         uint64_t memory_map_size);
  76
  77 /* channel_handle_add_stream - for consumer. */
  78 extern
  79 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  80                 int shm_fd, int wait_fd, uint64_t memory_map_size);
  81
  82 /*
  83  * channel_destroy finalizes all channel's buffers, waits for readers to
  84  * release all references, and destroys the channel.
  85  */
  86 extern
  87 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  88                 int shadow);
  89
  90
  91 /* Buffer read operations */
  92
  93 /*
  94  * Iteration on channel cpumask needs to issue a read barrier to match the write
  95  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  96  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  97  * only performed at channel destruction.
  98  */
  99 #define for_each_channel_cpu(cpu, chan)                                 \
 100         for_each_possible_cpu(cpu)
 101
 102 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
 103                                 const struct lttng_ust_lib_ring_buffer_config *config,
 104                                 struct channel *chan, int cpu,
 105                                 struct lttng_ust_shm_handle *handle,
 106                                 int **shm_fd, char **shm_path,
 107                                 int **wait_fd, char **wait_pipe_path,
 108                                 uint64_t **memory_map_size);
 109 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 110                                      struct lttng_ust_shm_handle *handle,
 111                                      int shadow);
 112 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 113                                          struct lttng_ust_shm_handle *handle,
 114                                          int shadow);
 115
 116 /*
 117  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 118  */
 119 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 120                                     unsigned long *consumed,
 121                                     unsigned long *produced,
 122                                     struct lttng_ust_shm_handle *handle);
 123 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 124                                           unsigned long consumed_new,
 125                                           struct lttng_ust_shm_handle *handle);
 126
 127 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 128                                       unsigned long consumed,
 129                                       struct lttng_ust_shm_handle *handle);
 130 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 131                                        struct lttng_ust_shm_handle *handle);
 132
 133 /*
 134  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 135  * to read sub-buffers sequentially.
 136  */
 137 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 138                                                   struct lttng_ust_shm_handle *handle)
 139 {
 140         int ret;
 141
 142         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 143                                        &buf->prod_snapshot, handle);
 144         if (ret)
 145                 return ret;
 146         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 147         return ret;
 148 }
 149
 150 static inline
 151 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 152                                      struct lttng_ust_shm_handle *handle)
 153 {
 154         lib_ring_buffer_put_subbuf(buf, handle);
 155         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 156                                                         shmp(handle, buf->backend.chan)), handle);
 157 }
 158
 159 extern void channel_reset(struct channel *chan);
 160 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 161                                   struct lttng_ust_shm_handle *handle);
 162
 163 static inline
 164 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 165                                          struct lttng_ust_lib_ring_buffer *buf)
 166 {
 167         return v_read(config, &buf->offset);
 168 }
 169
 170 static inline
 171 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 172                                            struct lttng_ust_lib_ring_buffer *buf)
 173 {
 174         return uatomic_read(&buf->consumed);
 175 }
 176
 177 /*
 178  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 179  * ordering enforced with respect to trace teardown).
 180  */
 181 static inline
 182 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 183                                  struct lttng_ust_lib_ring_buffer *buf)
 184 {
 185         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 186         /*
 187          * Read finalized before counters.
 188          */
 189         cmm_smp_rmb();
 190         return finalized;
 191 }
 192
 193 static inline
 194 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 195 {
 196         return chan->finalized;
 197 }
 198
 199 static inline
 200 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 201 {
 202         return uatomic_read(&chan->record_disabled);
 203 }
 204
 205 static inline
 206 unsigned long lib_ring_buffer_get_read_data_size(
 207                                 const struct lttng_ust_lib_ring_buffer_config *config,
 208                                 struct lttng_ust_lib_ring_buffer *buf,
 209                                 struct lttng_ust_shm_handle *handle)
 210 {
 211         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 212 }
 213
 214 static inline
 215 unsigned long lib_ring_buffer_get_records_count(
 216                                 const struct lttng_ust_lib_ring_buffer_config *config,
 217                                 struct lttng_ust_lib_ring_buffer *buf)
 218 {
 219         return v_read(config, &buf->records_count);
 220 }
 221
 222 static inline
 223 unsigned long lib_ring_buffer_get_records_overrun(
 224                                 const struct lttng_ust_lib_ring_buffer_config *config,
 225                                 struct lttng_ust_lib_ring_buffer *buf)
 226 {
 227         return v_read(config, &buf->records_overrun);
 228 }
 229
 230 static inline
 231 unsigned long lib_ring_buffer_get_records_lost_full(
 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_lost_full);
 236 }
 237
 238 static inline
 239 unsigned long lib_ring_buffer_get_records_lost_wrap(
 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_lost_wrap);
 244 }
 245
 246 static inline
 247 unsigned long lib_ring_buffer_get_records_lost_big(
 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_big);
 252 }
 253
 254 static inline
 255 unsigned long lib_ring_buffer_get_records_read(
 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->backend.records_read);
 260 }
 261
 262 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */