libringbuffer/frontend.h

   1 #ifndef _LINUX_RING_BUFFER_FRONTEND_H
   2 #define _LINUX_RING_BUFFER_FRONTEND_H
   3
   4 /*
   5  * linux/ringbuffer/frontend.h
   6  *
   7  * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Ring Buffer Library Synchronization Header (API).
  10  *
  11  * Author:
  12  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  13  *
  14  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  15  *
  16  * Dual LGPL v2.1/GPL v2 license.
  17  */
  18
  19 #include <urcu/compiler.h>
  20 #include <urcu/uatomic.h>
  21
  22 #include "smp.h"
  23 /* Internal helpers */
  24 #include "frontend_internal.h"
  25
  26 /* Buffer creation/removal and setup operations */
  27
  28 /*
  29  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  30  * padding to let readers get those sub-buffers.  Used for live streaming.
  31  *
  32  * read_timer_interval is the time interval (in us) to wake up pending readers.
  33  *
  34  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  35  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  36  * be set to NULL for other backends.
  37  *
  38  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  39  * memory area for client-specific data. This memory is managed by lib
  40  * ring buffer. priv_data_align is the alignment required for the
  41  * private data area.
  42  */
  43
  44 extern
  45 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  46                                 const char *name,
  47                                 void **priv_data,
  48                                 size_t priv_data_align,
  49                                 size_t priv_data_size,
  50                                 void *priv_data_init,
  51                                 void *buf_addr,
  52                                 size_t subbuf_size, size_t num_subbuf,
  53                                 unsigned int switch_timer_interval,
  54                                 unsigned int read_timer_interval,
  55                                 int **shm_fd, int **wait_fd,
  56                                 uint64_t **memory_map_size);
  57
  58 /* channel_handle_create - for consumer. */
  59 extern
  60 struct lttng_ust_shm_handle *channel_handle_create(int shm_fd, int wait_fd,
  61                                         uint64_t memory_map_size);
  62
  63 /* channel_handle_add_stream - for consumer. */
  64 extern
  65 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  66                 int shm_fd, int wait_fd, uint64_t memory_map_size);
  67
  68 /*
  69  * channel_destroy finalizes all channel's buffers, waits for readers to
  70  * release all references, and destroys the channel.
  71  */
  72 extern
  73 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  74                 int shadow);
  75
  76
  77 /* Buffer read operations */
  78
  79 /*
  80  * Iteration on channel cpumask needs to issue a read barrier to match the write
  81  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  82  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  83  * only performed at channel destruction.
  84  */
  85 #define for_each_channel_cpu(cpu, chan)                                 \
  86         for_each_possible_cpu(cpu)
  87
  88 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  89                                 const struct lttng_ust_lib_ring_buffer_config *config,
  90                                 struct channel *chan, int cpu,
  91                                 struct lttng_ust_shm_handle *handle,
  92                                 int **shm_fd, int **wait_fd,
  93                                 uint64_t **memory_map_size);
  94 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
  95                                      struct lttng_ust_shm_handle *handle,
  96                                      int shadow);
  97 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
  98                                          struct lttng_ust_shm_handle *handle,
  99                                          int shadow);
 100
 101 /*
 102  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 103  */
 104 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 105                                     unsigned long *consumed,
 106                                     unsigned long *produced,
 107                                     struct lttng_ust_shm_handle *handle);
 108 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 109                                           unsigned long consumed_new,
 110                                           struct lttng_ust_shm_handle *handle);
 111
 112 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 113                                       unsigned long consumed,
 114                                       struct lttng_ust_shm_handle *handle);
 115 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 116                                        struct lttng_ust_shm_handle *handle);
 117
 118 /*
 119  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 120  * to read sub-buffers sequentially.
 121  */
 122 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 123                                                   struct lttng_ust_shm_handle *handle)
 124 {
 125         int ret;
 126
 127         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 128                                        &buf->prod_snapshot, handle);
 129         if (ret)
 130                 return ret;
 131         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 132         return ret;
 133 }
 134
 135 static inline
 136 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 137                                      struct lttng_ust_shm_handle *handle)
 138 {
 139         lib_ring_buffer_put_subbuf(buf, handle);
 140         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 141                                                         shmp(handle, buf->backend.chan)), handle);
 142 }
 143
 144 extern void channel_reset(struct channel *chan);
 145 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 146                                   struct lttng_ust_shm_handle *handle);
 147
 148 static inline
 149 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 150                                          struct lttng_ust_lib_ring_buffer *buf)
 151 {
 152         return v_read(config, &buf->offset);
 153 }
 154
 155 static inline
 156 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 157                                            struct lttng_ust_lib_ring_buffer *buf)
 158 {
 159         return uatomic_read(&buf->consumed);
 160 }
 161
 162 /*
 163  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 164  * ordering enforced with respect to trace teardown).
 165  */
 166 static inline
 167 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 168                                  struct lttng_ust_lib_ring_buffer *buf)
 169 {
 170         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 171         /*
 172          * Read finalized before counters.
 173          */
 174         cmm_smp_rmb();
 175         return finalized;
 176 }
 177
 178 static inline
 179 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 180 {
 181         return chan->finalized;
 182 }
 183
 184 static inline
 185 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 186 {
 187         return uatomic_read(&chan->record_disabled);
 188 }
 189
 190 static inline
 191 unsigned long lib_ring_buffer_get_read_data_size(
 192                                 const struct lttng_ust_lib_ring_buffer_config *config,
 193                                 struct lttng_ust_lib_ring_buffer *buf,
 194                                 struct lttng_ust_shm_handle *handle)
 195 {
 196         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 197 }
 198
 199 static inline
 200 unsigned long lib_ring_buffer_get_records_count(
 201                                 const struct lttng_ust_lib_ring_buffer_config *config,
 202                                 struct lttng_ust_lib_ring_buffer *buf)
 203 {
 204         return v_read(config, &buf->records_count);
 205 }
 206
 207 static inline
 208 unsigned long lib_ring_buffer_get_records_overrun(
 209                                 const struct lttng_ust_lib_ring_buffer_config *config,
 210                                 struct lttng_ust_lib_ring_buffer *buf)
 211 {
 212         return v_read(config, &buf->records_overrun);
 213 }
 214
 215 static inline
 216 unsigned long lib_ring_buffer_get_records_lost_full(
 217                                 const struct lttng_ust_lib_ring_buffer_config *config,
 218                                 struct lttng_ust_lib_ring_buffer *buf)
 219 {
 220         return v_read(config, &buf->records_lost_full);
 221 }
 222
 223 static inline
 224 unsigned long lib_ring_buffer_get_records_lost_wrap(
 225                                 const struct lttng_ust_lib_ring_buffer_config *config,
 226                                 struct lttng_ust_lib_ring_buffer *buf)
 227 {
 228         return v_read(config, &buf->records_lost_wrap);
 229 }
 230
 231 static inline
 232 unsigned long lib_ring_buffer_get_records_lost_big(
 233                                 const struct lttng_ust_lib_ring_buffer_config *config,
 234                                 struct lttng_ust_lib_ring_buffer *buf)
 235 {
 236         return v_read(config, &buf->records_lost_big);
 237 }
 238
 239 static inline
 240 unsigned long lib_ring_buffer_get_records_read(
 241                                 const struct lttng_ust_lib_ring_buffer_config *config,
 242                                 struct lttng_ust_lib_ring_buffer *buf)
 243 {
 244         return v_read(config, &buf->backend.records_read);
 245 }
 246
 247 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */