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 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 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf);
  71 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf);
  72
  73 /*
  74  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  75  */
  76 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
  77                                     unsigned long *consumed,
  78                                     unsigned long *produced);
  79 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
  80                                           unsigned long consumed_new);
  81
  82 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
  83                                       unsigned long consumed);
  84 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf);
  85
  86 /*
  87  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
  88  * to read sub-buffers sequentially.
  89  */
  90 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf)
  91 {
  92         int ret;
  93
  94         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
  95                                        &buf->prod_snapshot);
  96         if (ret)
  97                 return ret;
  98         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot);
  99         return ret;
 100 }
 101
 102 static inline void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf)
 103 {
 104         lib_ring_buffer_put_subbuf(buf);
 105         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 106                                                     shmp(buf->backend.chan)));
 107 }
 108
 109 extern void channel_reset(struct channel *chan);
 110 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf);
 111
 112 static inline
 113 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 114                                          struct lib_ring_buffer *buf)
 115 {
 116         return v_read(config, &buf->offset);
 117 }
 118
 119 static inline
 120 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 121                                            struct lib_ring_buffer *buf)
 122 {
 123         return uatomic_read(&buf->consumed);
 124 }
 125
 126 /*
 127  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 128  * ordering enforced with respect to trace teardown).
 129  */
 130 static inline
 131 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 132                                  struct lib_ring_buffer *buf)
 133 {
 134         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 135         /*
 136          * Read finalized before counters.
 137          */
 138         cmm_smp_rmb();
 139         return finalized;
 140 }
 141
 142 static inline
 143 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 144 {
 145         return chan->finalized;
 146 }
 147
 148 static inline
 149 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 150 {
 151         return uatomic_read(&chan->record_disabled);
 152 }
 153
 154 static inline
 155 unsigned long lib_ring_buffer_get_read_data_size(
 156                                 const struct lib_ring_buffer_config *config,
 157                                 struct lib_ring_buffer *buf)
 158 {
 159         return subbuffer_get_read_data_size(config, &buf->backend);
 160 }
 161
 162 static inline
 163 unsigned long lib_ring_buffer_get_records_count(
 164                                 const struct lib_ring_buffer_config *config,
 165                                 struct lib_ring_buffer *buf)
 166 {
 167         return v_read(config, &buf->records_count);
 168 }
 169
 170 static inline
 171 unsigned long lib_ring_buffer_get_records_overrun(
 172                                 const struct lib_ring_buffer_config *config,
 173                                 struct lib_ring_buffer *buf)
 174 {
 175         return v_read(config, &buf->records_overrun);
 176 }
 177
 178 static inline
 179 unsigned long lib_ring_buffer_get_records_lost_full(
 180                                 const struct lib_ring_buffer_config *config,
 181                                 struct lib_ring_buffer *buf)
 182 {
 183         return v_read(config, &buf->records_lost_full);
 184 }
 185
 186 static inline
 187 unsigned long lib_ring_buffer_get_records_lost_wrap(
 188                                 const struct lib_ring_buffer_config *config,
 189                                 struct lib_ring_buffer *buf)
 190 {
 191         return v_read(config, &buf->records_lost_wrap);
 192 }
 193
 194 static inline
 195 unsigned long lib_ring_buffer_get_records_lost_big(
 196                                 const struct lib_ring_buffer_config *config,
 197                                 struct lib_ring_buffer *buf)
 198 {
 199         return v_read(config, &buf->records_lost_big);
 200 }
 201
 202 static inline
 203 unsigned long lib_ring_buffer_get_records_read(
 204                                 const struct lib_ring_buffer_config *config,
 205                                 struct lib_ring_buffer *buf)
 206 {
 207         return v_read(config, &buf->backend.records_read);
 208 }
 209
 210 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */