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 char *shm_path);
  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         lib_ring_buffer_put_subbuf(buf, handle);
 166         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 167                                                         shmp(handle, buf->backend.chan)), handle);
 168 }
 169
 170 extern void channel_reset(struct channel *chan);
 171 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 172                                   struct lttng_ust_shm_handle *handle);
 173
 174 static inline
 175 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 176                                          struct lttng_ust_lib_ring_buffer *buf)
 177 {
 178         return v_read(config, &buf->offset);
 179 }
 180
 181 static inline
 182 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 183                                            struct lttng_ust_lib_ring_buffer *buf)
 184 {
 185         return uatomic_read(&buf->consumed);
 186 }
 187
 188 /*
 189  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 190  * ordering enforced with respect to trace teardown).
 191  */
 192 static inline
 193 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 194                                  struct lttng_ust_lib_ring_buffer *buf)
 195 {
 196         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 197         /*
 198          * Read finalized before counters.
 199          */
 200         cmm_smp_rmb();
 201         return finalized;
 202 }
 203
 204 static inline
 205 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 206 {
 207         return chan->finalized;
 208 }
 209
 210 static inline
 211 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 212 {
 213         return uatomic_read(&chan->record_disabled);
 214 }
 215
 216 static inline
 217 unsigned long lib_ring_buffer_get_read_data_size(
 218                                 const struct lttng_ust_lib_ring_buffer_config *config,
 219                                 struct lttng_ust_lib_ring_buffer *buf,
 220                                 struct lttng_ust_shm_handle *handle)
 221 {
 222         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 223 }
 224
 225 static inline
 226 unsigned long lib_ring_buffer_get_records_count(
 227                                 const struct lttng_ust_lib_ring_buffer_config *config,
 228                                 struct lttng_ust_lib_ring_buffer *buf)
 229 {
 230         return v_read(config, &buf->records_count);
 231 }
 232
 233 static inline
 234 unsigned long lib_ring_buffer_get_records_overrun(
 235                                 const struct lttng_ust_lib_ring_buffer_config *config,
 236                                 struct lttng_ust_lib_ring_buffer *buf)
 237 {
 238         return v_read(config, &buf->records_overrun);
 239 }
 240
 241 static inline
 242 unsigned long lib_ring_buffer_get_records_lost_full(
 243                                 const struct lttng_ust_lib_ring_buffer_config *config,
 244                                 struct lttng_ust_lib_ring_buffer *buf)
 245 {
 246         return v_read(config, &buf->records_lost_full);
 247 }
 248
 249 static inline
 250 unsigned long lib_ring_buffer_get_records_lost_wrap(
 251                                 const struct lttng_ust_lib_ring_buffer_config *config,
 252                                 struct lttng_ust_lib_ring_buffer *buf)
 253 {
 254         return v_read(config, &buf->records_lost_wrap);
 255 }
 256
 257 static inline
 258 unsigned long lib_ring_buffer_get_records_lost_big(
 259                                 const struct lttng_ust_lib_ring_buffer_config *config,
 260                                 struct lttng_ust_lib_ring_buffer *buf)
 261 {
 262         return v_read(config, &buf->records_lost_big);
 263 }
 264
 265 static inline
 266 unsigned long lib_ring_buffer_get_records_read(
 267                                 const struct lttng_ust_lib_ring_buffer_config *config,
 268                                 struct lttng_ust_lib_ring_buffer *buf)
 269 {
 270         return v_read(config, &buf->backend.records_read);
 271 }
 272
 273 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */