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
  39 extern
  40 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  41                                 const char *name, void *priv,
  42                                 void *buf_addr,
  43                                 size_t subbuf_size, size_t num_subbuf,
  44                                 unsigned int switch_timer_interval,
  45                                 unsigned int read_timer_interval,
  46                                 int *shm_fd, int *wait_fd,
  47                                 uint64_t *memory_map_size);
  48
  49 /* channel_handle_create - for consumer. */
  50 extern
  51 struct lttng_ust_shm_handle *channel_handle_create(int shm_fd, int wait_fd,
  52                                         uint64_t memory_map_size);
  53
  54 /* channel_handle_add_stream - for consumer. */
  55 extern
  56 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  57                 int shm_fd, int wait_fd, uint64_t memory_map_size);
  58
  59 /*
  60  * channel_destroy returns the private data pointer. It finalizes all channel's
  61  * buffers, waits for readers to release all references, and destroys the
  62  * channel.
  63  */
  64 extern
  65 void *channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  66                 int shadow);
  67
  68
  69 /* Buffer read operations */
  70
  71 /*
  72  * Iteration on channel cpumask needs to issue a read barrier to match the write
  73  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  74  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  75  * only performed at channel destruction.
  76  */
  77 #define for_each_channel_cpu(cpu, chan)                                 \
  78         for_each_possible_cpu(cpu)
  79
  80 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  81                                 const struct lttng_ust_lib_ring_buffer_config *config,
  82                                 struct channel *chan, int cpu,
  83                                 struct lttng_ust_shm_handle *handle,
  84                                 int *shm_fd, int *wait_fd,
  85                                 uint64_t *memory_map_size);
  86 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
  87                                      struct lttng_ust_shm_handle *handle,
  88                                      int shadow);
  89 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
  90                                          struct lttng_ust_shm_handle *handle,
  91                                          int shadow);
  92
  93 /*
  94  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  95  */
  96 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
  97                                     unsigned long *consumed,
  98                                     unsigned long *produced,
  99                                     struct lttng_ust_shm_handle *handle);
 100 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 101                                           unsigned long consumed_new,
 102                                           struct lttng_ust_shm_handle *handle);
 103
 104 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 105                                       unsigned long consumed,
 106                                       struct lttng_ust_shm_handle *handle);
 107 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 108                                        struct lttng_ust_shm_handle *handle);
 109
 110 /*
 111  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 112  * to read sub-buffers sequentially.
 113  */
 114 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 115                                                   struct lttng_ust_shm_handle *handle)
 116 {
 117         int ret;
 118
 119         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 120                                        &buf->prod_snapshot, handle);
 121         if (ret)
 122                 return ret;
 123         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 124         return ret;
 125 }
 126
 127 static inline
 128 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 129                                      struct lttng_ust_shm_handle *handle)
 130 {
 131         lib_ring_buffer_put_subbuf(buf, handle);
 132         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 133                                                         shmp(handle, buf->backend.chan)), handle);
 134 }
 135
 136 extern void channel_reset(struct channel *chan);
 137 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 138                                   struct lttng_ust_shm_handle *handle);
 139
 140 static inline
 141 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 142                                          struct lttng_ust_lib_ring_buffer *buf)
 143 {
 144         return v_read(config, &buf->offset);
 145 }
 146
 147 static inline
 148 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 149                                            struct lttng_ust_lib_ring_buffer *buf)
 150 {
 151         return uatomic_read(&buf->consumed);
 152 }
 153
 154 /*
 155  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 156  * ordering enforced with respect to trace teardown).
 157  */
 158 static inline
 159 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 160                                  struct lttng_ust_lib_ring_buffer *buf)
 161 {
 162         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 163         /*
 164          * Read finalized before counters.
 165          */
 166         cmm_smp_rmb();
 167         return finalized;
 168 }
 169
 170 static inline
 171 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 172 {
 173         return chan->finalized;
 174 }
 175
 176 static inline
 177 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 178 {
 179         return uatomic_read(&chan->record_disabled);
 180 }
 181
 182 static inline
 183 unsigned long lib_ring_buffer_get_read_data_size(
 184                                 const struct lttng_ust_lib_ring_buffer_config *config,
 185                                 struct lttng_ust_lib_ring_buffer *buf,
 186                                 struct lttng_ust_shm_handle *handle)
 187 {
 188         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 189 }
 190
 191 static inline
 192 unsigned long lib_ring_buffer_get_records_count(
 193                                 const struct lttng_ust_lib_ring_buffer_config *config,
 194                                 struct lttng_ust_lib_ring_buffer *buf)
 195 {
 196         return v_read(config, &buf->records_count);
 197 }
 198
 199 static inline
 200 unsigned long lib_ring_buffer_get_records_overrun(
 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_overrun);
 205 }
 206
 207 static inline
 208 unsigned long lib_ring_buffer_get_records_lost_full(
 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_lost_full);
 213 }
 214
 215 static inline
 216 unsigned long lib_ring_buffer_get_records_lost_wrap(
 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_wrap);
 221 }
 222
 223 static inline
 224 unsigned long lib_ring_buffer_get_records_lost_big(
 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_big);
 229 }
 230
 231 static inline
 232 unsigned long lib_ring_buffer_get_records_read(
 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->backend.records_read);
 237 }
 238
 239 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */