lib/ringbuffer/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 <linux/pipe_fs_i.h>
  20 #include <linux/rcupdate.h>
  21 #include <linux/cpumask.h>
  22 #include <linux/module.h>
  23 #include <linux/bitops.h>
  24 #include <linux/splice.h>
  25 #include <linux/string.h>
  26 #include <linux/timer.h>
  27 #include <linux/sched.h>
  28 #include <linux/cache.h>
  29 #include <linux/time.h>
  30 #include <linux/slab.h>
  31 #include <linux/init.h>
  32 #include <linux/stat.h>
  33 #include <linux/cpu.h>
  34 #include <linux/fs.h>
  35
  36 #include <asm/atomic.h>
  37 #include <asm/local.h>
  38
  39 /* Internal helpers */
  40 #include "../../wrapper/ringbuffer/frontend_internal.h"
  41
  42 /* Buffer creation/removal and setup operations */
  43
  44 /*
  45  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  46  * padding to let readers get those sub-buffers.  Used for live streaming.
  47  *
  48  * read_timer_interval is the time interval (in us) to wake up pending readers.
  49  *
  50  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  51  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  52  * be set to NULL for other backends.
  53  */
  54
  55 extern
  56 struct channel *channel_create(const struct lib_ring_buffer_config *config,
  57                                const char *name, void *priv,
  58                                void *buf_addr,
  59                                size_t subbuf_size, size_t num_subbuf,
  60                                unsigned int switch_timer_interval,
  61                                unsigned int read_timer_interval);
  62
  63 /*
  64  * channel_destroy returns the private data pointer. It finalizes all channel's
  65  * buffers, waits for readers to release all references, and destroys the
  66  * channel.
  67  */
  68 extern
  69 void *channel_destroy(struct channel *chan);
  70
  71
  72 /* Buffer read operations */
  73
  74 /*
  75  * Iteration on channel cpumask needs to issue a read barrier to match the write
  76  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  77  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  78  * only performed at channel destruction.
  79  */
  80 #define for_each_channel_cpu(cpu, chan)                                 \
  81         for ((cpu) = -1;                                                \
  82                 ({ (cpu) = cpumask_next(cpu, (chan)->backend.cpumask);  \
  83                    smp_read_barrier_depends(); (cpu) < nr_cpu_ids; });)
  84
  85 extern struct lib_ring_buffer *channel_get_ring_buffer(
  86                                 const struct lib_ring_buffer_config *config,
  87                                 struct channel *chan, int cpu);
  88 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf);
  89 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf);
  90
  91 /*
  92  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
  93  */
  94 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
  95                                     unsigned long *consumed,
  96                                     unsigned long *produced);
  97 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
  98                                           unsigned long consumed_new);
  99
 100 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
 101                                       unsigned long consumed);
 102 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf);
 103
 104 /*
 105  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 106  * to read sub-buffers sequentially.
 107  */
 108 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf)
 109 {
 110         int ret;
 111
 112         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 113                                        &buf->prod_snapshot);
 114         if (ret)
 115                 return ret;
 116         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot);
 117         return ret;
 118 }
 119
 120 static inline void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf)
 121 {
 122         lib_ring_buffer_put_subbuf(buf);
 123         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 124                                                     buf->backend.chan));
 125 }
 126
 127 extern void channel_reset(struct channel *chan);
 128 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf);
 129
 130 static inline
 131 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 132                                          struct lib_ring_buffer *buf)
 133 {
 134         return v_read(config, &buf->offset);
 135 }
 136
 137 static inline
 138 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 139                                            struct lib_ring_buffer *buf)
 140 {
 141         return atomic_long_read(&buf->consumed);
 142 }
 143
 144 /*
 145  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 146  * ordering enforced with respect to trace teardown).
 147  */
 148 static inline
 149 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 150                                  struct lib_ring_buffer *buf)
 151 {
 152         int finalized = ACCESS_ONCE(buf->finalized);
 153         /*
 154          * Read finalized before counters.
 155          */
 156         smp_rmb();
 157         return finalized;
 158 }
 159
 160 static inline
 161 unsigned long lib_ring_buffer_get_read_data_size(
 162                                 const struct lib_ring_buffer_config *config,
 163                                 struct lib_ring_buffer *buf)
 164 {
 165         return subbuffer_get_read_data_size(config, &buf->backend);
 166 }
 167
 168 static inline
 169 unsigned long lib_ring_buffer_get_records_count(
 170                                 const struct lib_ring_buffer_config *config,
 171                                 struct lib_ring_buffer *buf)
 172 {
 173         return v_read(config, &buf->records_count);
 174 }
 175
 176 static inline
 177 unsigned long lib_ring_buffer_get_records_overrun(
 178                                 const struct lib_ring_buffer_config *config,
 179                                 struct lib_ring_buffer *buf)
 180 {
 181         return v_read(config, &buf->records_overrun);
 182 }
 183
 184 static inline
 185 unsigned long lib_ring_buffer_get_records_lost_full(
 186                                 const struct lib_ring_buffer_config *config,
 187                                 struct lib_ring_buffer *buf)
 188 {
 189         return v_read(config, &buf->records_lost_full);
 190 }
 191
 192 static inline
 193 unsigned long lib_ring_buffer_get_records_lost_wrap(
 194                                 const struct lib_ring_buffer_config *config,
 195                                 struct lib_ring_buffer *buf)
 196 {
 197         return v_read(config, &buf->records_lost_wrap);
 198 }
 199
 200 static inline
 201 unsigned long lib_ring_buffer_get_records_lost_big(
 202                                 const struct lib_ring_buffer_config *config,
 203                                 struct lib_ring_buffer *buf)
 204 {
 205         return v_read(config, &buf->records_lost_big);
 206 }
 207
 208 static inline
 209 unsigned long lib_ring_buffer_get_records_read(
 210                                 const struct lib_ring_buffer_config *config,
 211                                 struct lib_ring_buffer *buf)
 212 {
 213         return v_read(config, &buf->backend.records_read);
 214 }
 215
 216 static inline
 217 void *channel_get_private(struct channel *chan)
 218 {
 219         return chan->backend.priv;
 220 }
 221
 222 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */