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
  69 /*
  70  * channel_destroy finalizes all channel's buffers, waits for readers to
  71  * release all references, and destroys the channel.
  72  */
  73 extern
  74 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  75                 int consumer);
  76
  77
  78 /* Buffer read operations */
  79
  80 /*
  81  * Iteration on channel cpumask needs to issue a read barrier to match the write
  82  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  83  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  84  * only performed at channel destruction.
  85  */
  86 #define for_each_channel_cpu(cpu, chan)                                 \
  87         for_each_possible_cpu(cpu)
  88
  89 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  90                                 const struct lttng_ust_lib_ring_buffer_config *config,
  91                                 struct channel *chan, int cpu,
  92                                 struct lttng_ust_shm_handle *handle,
  93                                 int *shm_fd, int *wait_fd,
  94                                 int *wakeup_fd,
  95                                 uint64_t *memory_map_size);
  96 extern
  97 int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
  98                         struct channel *chan,
  99                         struct lttng_ust_shm_handle *handle);
 100 extern
 101 int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 102                         struct channel *chan,
 103                         struct lttng_ust_shm_handle *handle);
 104 extern
 105 int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 106                 struct channel *chan,
 107                 struct lttng_ust_shm_handle *handle,
 108                 int cpu);
 109 extern
 110 int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config,
 111                 struct channel *chan,
 112                 struct lttng_ust_shm_handle *handle,
 113                 int cpu);
 114
 115 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 116                                      struct lttng_ust_shm_handle *handle);
 117 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
 118                                          struct lttng_ust_shm_handle *handle);
 119
 120 /*
 121  * Initialize signals for ring buffer. Should be called early e.g. by
 122  * main() in the program to affect all threads.
 123  */
 124 void lib_ringbuffer_signal_init(void);
 125
 126 /*
 127  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 128  */
 129 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 130                                     unsigned long *consumed,
 131                                     unsigned long *produced,
 132                                     struct lttng_ust_shm_handle *handle);
 133 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 134                                           unsigned long consumed_new,
 135                                           struct lttng_ust_shm_handle *handle);
 136
 137 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 138                                       unsigned long consumed,
 139                                       struct lttng_ust_shm_handle *handle);
 140 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 141                                        struct lttng_ust_shm_handle *handle);
 142
 143 /*
 144  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 145  * to read sub-buffers sequentially.
 146  */
 147 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 148                                                   struct lttng_ust_shm_handle *handle)
 149 {
 150         int ret;
 151
 152         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 153                                        &buf->prod_snapshot, handle);
 154         if (ret)
 155                 return ret;
 156         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 157         return ret;
 158 }
 159
 160 static inline
 161 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 162                                      struct lttng_ust_shm_handle *handle)
 163 {
 164         lib_ring_buffer_put_subbuf(buf, handle);
 165         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 166                                                         shmp(handle, buf->backend.chan)), handle);
 167 }
 168
 169 extern void channel_reset(struct channel *chan);
 170 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 171                                   struct lttng_ust_shm_handle *handle);
 172
 173 static inline
 174 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 175                                          struct lttng_ust_lib_ring_buffer *buf)
 176 {
 177         return v_read(config, &buf->offset);
 178 }
 179
 180 static inline
 181 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 182                                            struct lttng_ust_lib_ring_buffer *buf)
 183 {
 184         return uatomic_read(&buf->consumed);
 185 }
 186
 187 /*
 188  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 189  * ordering enforced with respect to trace teardown).
 190  */
 191 static inline
 192 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 193                                  struct lttng_ust_lib_ring_buffer *buf)
 194 {
 195         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 196         /*
 197          * Read finalized before counters.
 198          */
 199         cmm_smp_rmb();
 200         return finalized;
 201 }
 202
 203 static inline
 204 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 205 {
 206         return chan->finalized;
 207 }
 208
 209 static inline
 210 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 211 {
 212         return uatomic_read(&chan->record_disabled);
 213 }
 214
 215 static inline
 216 unsigned long lib_ring_buffer_get_read_data_size(
 217                                 const struct lttng_ust_lib_ring_buffer_config *config,
 218                                 struct lttng_ust_lib_ring_buffer *buf,
 219                                 struct lttng_ust_shm_handle *handle)
 220 {
 221         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 222 }
 223
 224 static inline
 225 unsigned long lib_ring_buffer_get_records_count(
 226                                 const struct lttng_ust_lib_ring_buffer_config *config,
 227                                 struct lttng_ust_lib_ring_buffer *buf)
 228 {
 229         return v_read(config, &buf->records_count);
 230 }
 231
 232 static inline
 233 unsigned long lib_ring_buffer_get_records_overrun(
 234                                 const struct lttng_ust_lib_ring_buffer_config *config,
 235                                 struct lttng_ust_lib_ring_buffer *buf)
 236 {
 237         return v_read(config, &buf->records_overrun);
 238 }
 239
 240 static inline
 241 unsigned long lib_ring_buffer_get_records_lost_full(
 242                                 const struct lttng_ust_lib_ring_buffer_config *config,
 243                                 struct lttng_ust_lib_ring_buffer *buf)
 244 {
 245         return v_read(config, &buf->records_lost_full);
 246 }
 247
 248 static inline
 249 unsigned long lib_ring_buffer_get_records_lost_wrap(
 250                                 const struct lttng_ust_lib_ring_buffer_config *config,
 251                                 struct lttng_ust_lib_ring_buffer *buf)
 252 {
 253         return v_read(config, &buf->records_lost_wrap);
 254 }
 255
 256 static inline
 257 unsigned long lib_ring_buffer_get_records_lost_big(
 258                                 const struct lttng_ust_lib_ring_buffer_config *config,
 259                                 struct lttng_ust_lib_ring_buffer *buf)
 260 {
 261         return v_read(config, &buf->records_lost_big);
 262 }
 263
 264 static inline
 265 unsigned long lib_ring_buffer_get_records_read(
 266                                 const struct lttng_ust_lib_ring_buffer_config *config,
 267                                 struct lttng_ust_lib_ring_buffer *buf)
 268 {
 269         return v_read(config, &buf->backend.records_read);
 270 }
 271
 272 #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */