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 shm_handle *channel_create(const struct 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
  47 /*
  48  * channel_destroy returns the private data pointer. It finalizes all channel's
  49  * buffers, waits for readers to release all references, and destroys the
  50  * channel.
  51  */
  52 extern
  53 void *channel_destroy(struct channel *chan, struct shm_handle *handle);
  54
  55
  56 /* Buffer read operations */
  57
  58 /*
  59  * Iteration on channel cpumask needs to issue a read barrier to match the write
  60  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  61  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  62  * only performed at channel destruction.
  63  */
  64 #define for_each_channel_cpu(cpu, chan)                                 \
  65         for_each_possible_cpu(cpu)
  66
  67 extern struct lib_ring_buffer *channel_get_ring_buffer(
  68                                 const struct lib_ring_buffer_config *config,
  69                                 struct channel *chan, int cpu,
  70                                 struct shm_handle *handle,
  71                                 int *shm_fd, int *wait_fd,
  72                                 uint64_t *memory_map_size);
  73 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf,
  74                                      struct shm_handle *handle);
  75 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf,
  76                                          struct shm_handle *handle);
  77
  78 /*
  79  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  80  */
  81 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
  82                                     unsigned long *consumed,
  83                                     unsigned long *produced,
  84                                     struct shm_handle *handle);
  85 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
  86                                           unsigned long consumed_new,
  87                                           struct shm_handle *handle);
  88
  89 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
  90                                       unsigned long consumed,
  91                                       struct shm_handle *handle);
  92 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf,
  93                                        struct shm_handle *handle);
  94
  95 /*
  96  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
  97  * to read sub-buffers sequentially.
  98  */
  99 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf,
 100                                                   struct shm_handle *handle)
 101 {
 102         int ret;
 103
 104         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 105                                        &buf->prod_snapshot, handle);
 106         if (ret)
 107                 return ret;
 108         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 109         return ret;
 110 }
 111
 112 static inline
 113 void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf,
 114                                      struct shm_handle *handle)
 115 {
 116         lib_ring_buffer_put_subbuf(buf, handle);
 117         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 118                                                         shmp(handle, buf->backend.chan)), handle);
 119 }
 120
 121 extern void channel_reset(struct channel *chan);
 122 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf,
 123                                   struct shm_handle *handle);
 124
 125 static inline
 126 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 127                                          struct lib_ring_buffer *buf)
 128 {
 129         return v_read(config, &buf->offset);
 130 }
 131
 132 static inline
 133 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 134                                            struct lib_ring_buffer *buf)
 135 {
 136         return uatomic_read(&buf->consumed);
 137 }
 138
 139 /*
 140  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 141  * ordering enforced with respect to trace teardown).
 142  */
 143 static inline
 144 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 145                                  struct lib_ring_buffer *buf)
 146 {
 147         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 148         /*
 149          * Read finalized before counters.
 150          */
 151         cmm_smp_rmb();
 152         return finalized;
 153 }
 154
 155 static inline
 156 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 157 {
 158         return chan->finalized;
 159 }
 160
 161 static inline
 162 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 163 {
 164         return uatomic_read(&chan->record_disabled);
 165 }
 166
 167 static inline
 168 unsigned long lib_ring_buffer_get_read_data_size(
 169                                 const struct lib_ring_buffer_config *config,
 170                                 struct lib_ring_buffer *buf,
 171                                 struct shm_handle *handle)
 172 {
 173         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 174 }
 175
 176 static inline
 177 unsigned long lib_ring_buffer_get_records_count(
 178                                 const struct lib_ring_buffer_config *config,
 179                                 struct lib_ring_buffer *buf)
 180 {
 181         return v_read(config, &buf->records_count);
 182 }
 183
 184 static inline
 185 unsigned long lib_ring_buffer_get_records_overrun(
 186                                 const struct lib_ring_buffer_config *config,
 187                                 struct lib_ring_buffer *buf)
 188 {
 189         return v_read(config, &buf->records_overrun);
 190 }
 191
 192 static inline
 193 unsigned long lib_ring_buffer_get_records_lost_full(
 194                                 const struct lib_ring_buffer_config *config,
 195                                 struct lib_ring_buffer *buf)
 196 {
 197         return v_read(config, &buf->records_lost_full);
 198 }
 199
 200 static inline
 201 unsigned long lib_ring_buffer_get_records_lost_wrap(
 202                                 const struct lib_ring_buffer_config *config,
 203                                 struct lib_ring_buffer *buf)
 204 {
 205         return v_read(config, &buf->records_lost_wrap);
 206 }
 207
 208 static inline
 209 unsigned long lib_ring_buffer_get_records_lost_big(
 210                                 const struct lib_ring_buffer_config *config,
 211                                 struct lib_ring_buffer *buf)
 212 {
 213         return v_read(config, &buf->records_lost_big);
 214 }
 215
 216 static inline
 217 unsigned long lib_ring_buffer_get_records_read(
 218                                 const struct lib_ring_buffer_config *config,
 219                                 struct lib_ring_buffer *buf)
 220 {
 221         return v_read(config, &buf->backend.records_read);
 222 }
 223
 224 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */