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 /* Internal helpers */
  23 #include "frontend_internal.h"
  24
  25 /* Buffer creation/removal and setup operations */
  26
  27 /*
  28  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  29  * padding to let readers get those sub-buffers.  Used for live streaming.
  30  *
  31  * read_timer_interval is the time interval (in us) to wake up pending readers.
  32  *
  33  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  34  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  35  * be set to NULL for other backends.
  36  */
  37
  38 extern
  39 struct channel *channel_create(const struct lib_ring_buffer_config *config,
  40                                const char *name, void *priv,
  41                                void *buf_addr,
  42                                size_t subbuf_size, size_t num_subbuf,
  43                                unsigned int switch_timer_interval,
  44                                unsigned int read_timer_interval);
  45
  46 /*
  47  * channel_destroy returns the private data pointer. It finalizes all channel's
  48  * buffers, waits for readers to release all references, and destroys the
  49  * channel.
  50  */
  51 extern
  52 void *channel_destroy(struct channel *chan);
  53
  54
  55 /* Buffer read operations */
  56
  57 /*
  58  * Iteration on channel cpumask needs to issue a read barrier to match the write
  59  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  60  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  61  * only performed at channel destruction.
  62  */
  63 #define for_each_channel_cpu(cpu, chan)                                 \
  64         for ((cpu) = -1;                                                \
  65                 ({ (cpu) = cpumask_next(cpu, (chan)->backend.cpumask);  \
  66                    cmm_smp_read_barrier_depends(); (cpu) < nr_cpu_ids; });)
  67
  68 extern struct lib_ring_buffer *channel_get_ring_buffer(
  69                                 const struct lib_ring_buffer_config *config,
  70                                 struct channel *chan, int cpu);
  71 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf);
  72 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf);
  73
  74 /*
  75  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  76  */
  77 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
  78                                     unsigned long *consumed,
  79                                     unsigned long *produced);
  80 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
  81                                           unsigned long consumed_new);
  82
  83 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
  84                                       unsigned long consumed);
  85 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf);
  86
  87 /*
  88  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
  89  * to read sub-buffers sequentially.
  90  */
  91 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf)
  92 {
  93         int ret;
  94
  95         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
  96                                        &buf->prod_snapshot);
  97         if (ret)
  98                 return ret;
  99         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot);
 100         return ret;
 101 }
 102
 103 static inline void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf)
 104 {
 105         lib_ring_buffer_put_subbuf(buf);
 106         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 107                                                     buf->backend.chan));
 108 }
 109
 110 extern void channel_reset(struct channel *chan);
 111 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf);
 112
 113 static inline
 114 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 115                                          struct lib_ring_buffer *buf)
 116 {
 117         return v_read(config, &buf->offset);
 118 }
 119
 120 static inline
 121 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 122                                            struct lib_ring_buffer *buf)
 123 {
 124         return uatomic_read(&buf->consumed);
 125 }
 126
 127 /*
 128  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 129  * ordering enforced with respect to trace teardown).
 130  */
 131 static inline
 132 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 133                                  struct lib_ring_buffer *buf)
 134 {
 135         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 136         /*
 137          * Read finalized before counters.
 138          */
 139         cmm_smp_rmb();
 140         return finalized;
 141 }
 142
 143 static inline
 144 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 145 {
 146         return chan->finalized;
 147 }
 148
 149 static inline
 150 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 151 {
 152         return uatomic_read(&chan->record_disabled);
 153 }
 154
 155 static inline
 156 unsigned long lib_ring_buffer_get_read_data_size(
 157                                 const struct lib_ring_buffer_config *config,
 158                                 struct lib_ring_buffer *buf)
 159 {
 160         return subbuffer_get_read_data_size(config, &buf->backend);
 161 }
 162
 163 static inline
 164 unsigned long lib_ring_buffer_get_records_count(
 165                                 const struct lib_ring_buffer_config *config,
 166                                 struct lib_ring_buffer *buf)
 167 {
 168         return v_read(config, &buf->records_count);
 169 }
 170
 171 static inline
 172 unsigned long lib_ring_buffer_get_records_overrun(
 173                                 const struct lib_ring_buffer_config *config,
 174                                 struct lib_ring_buffer *buf)
 175 {
 176         return v_read(config, &buf->records_overrun);
 177 }
 178
 179 static inline
 180 unsigned long lib_ring_buffer_get_records_lost_full(
 181                                 const struct lib_ring_buffer_config *config,
 182                                 struct lib_ring_buffer *buf)
 183 {
 184         return v_read(config, &buf->records_lost_full);
 185 }
 186
 187 static inline
 188 unsigned long lib_ring_buffer_get_records_lost_wrap(
 189                                 const struct lib_ring_buffer_config *config,
 190                                 struct lib_ring_buffer *buf)
 191 {
 192         return v_read(config, &buf->records_lost_wrap);
 193 }
 194
 195 static inline
 196 unsigned long lib_ring_buffer_get_records_lost_big(
 197                                 const struct lib_ring_buffer_config *config,
 198                                 struct lib_ring_buffer *buf)
 199 {
 200         return v_read(config, &buf->records_lost_big);
 201 }
 202
 203 static inline
 204 unsigned long lib_ring_buffer_get_records_read(
 205                                 const struct lib_ring_buffer_config *config,
 206                                 struct lib_ring_buffer *buf)
 207 {
 208         return v_read(config, &buf->backend.records_read);
 209 }
 210
 211 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */