lib/ringbuffer/frontend.h

   1 #ifndef _LIB_RING_BUFFER_FRONTEND_H
   2 #define _LIB_RING_BUFFER_FRONTEND_H
   3
   4 /*
   5  * lib/ringbuffer/frontend.h
   6  *
   7  * Ring Buffer Library Synchronization Header (API).
   8  *
   9  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; only
  14  * version 2.1 of the License.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  24  *
  25  * Author:
  26  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  27  *
  28  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  29  */
  30
  31 #include <linux/pipe_fs_i.h>
  32 #include <linux/rcupdate.h>
  33 #include <linux/cpumask.h>
  34 #include <linux/module.h>
  35 #include <linux/bitops.h>
  36 #include <linux/splice.h>
  37 #include <linux/string.h>
  38 #include <linux/timer.h>
  39 #include <linux/sched.h>
  40 #include <linux/cache.h>
  41 #include <linux/time.h>
  42 #include <linux/slab.h>
  43 #include <linux/init.h>
  44 #include <linux/stat.h>
  45 #include <linux/cpu.h>
  46 #include <linux/fs.h>
  47
  48 #include <asm/atomic.h>
  49 #include <asm/local.h>
  50
  51 /* Internal helpers */
  52 #include <wrapper/ringbuffer/frontend_internal.h>
  53
  54 /* Buffer creation/removal and setup operations */
  55
  56 /*
  57  * switch_timer_interval is the time interval (in us) to fill sub-buffers with
  58  * padding to let readers get those sub-buffers.  Used for live streaming.
  59  *
  60  * read_timer_interval is the time interval (in us) to wake up pending readers.
  61  *
  62  * buf_addr is a pointer the the beginning of the preallocated buffer contiguous
  63  * address mapping. It is used only by RING_BUFFER_STATIC configuration. It can
  64  * be set to NULL for other backends.
  65  */
  66
  67 extern
  68 struct channel *channel_create(const struct lib_ring_buffer_config *config,
  69                                const char *name, void *priv,
  70                                void *buf_addr,
  71                                size_t subbuf_size, size_t num_subbuf,
  72                                unsigned int switch_timer_interval,
  73                                unsigned int read_timer_interval);
  74
  75 /*
  76  * channel_destroy returns the private data pointer. It finalizes all channel's
  77  * buffers, waits for readers to release all references, and destroys the
  78  * channel.
  79  */
  80 extern
  81 void *channel_destroy(struct channel *chan);
  82
  83
  84 /* Buffer read operations */
  85
  86 /*
  87  * Iteration on channel cpumask needs to issue a read barrier to match the write
  88  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  89  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  90  * only performed at channel destruction.
  91  */
  92 #define for_each_channel_cpu(cpu, chan)                                 \
  93         for ((cpu) = -1;                                                \
  94                 ({ (cpu) = cpumask_next(cpu, (chan)->backend.cpumask);  \
  95                    smp_read_barrier_depends(); (cpu) < nr_cpu_ids; });)
  96
  97 extern struct lib_ring_buffer *channel_get_ring_buffer(
  98                                 const struct lib_ring_buffer_config *config,
  99                                 struct channel *chan, int cpu);
 100 extern int lib_ring_buffer_open_read(struct lib_ring_buffer *buf);
 101 extern void lib_ring_buffer_release_read(struct lib_ring_buffer *buf);
 102
 103 /*
 104  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 105  */
 106 extern int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
 107                                     unsigned long *consumed,
 108                                     unsigned long *produced);
 109 extern void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
 110                                           unsigned long consumed_new);
 111
 112 extern int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
 113                                       unsigned long consumed);
 114 extern void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf);
 115
 116 /*
 117  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 118  * to read sub-buffers sequentially.
 119  */
 120 static inline int lib_ring_buffer_get_next_subbuf(struct lib_ring_buffer *buf)
 121 {
 122         int ret;
 123
 124         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 125                                        &buf->prod_snapshot);
 126         if (ret)
 127                 return ret;
 128         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot);
 129         return ret;
 130 }
 131
 132 static inline void lib_ring_buffer_put_next_subbuf(struct lib_ring_buffer *buf)
 133 {
 134         lib_ring_buffer_put_subbuf(buf);
 135         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 136                                                     buf->backend.chan));
 137 }
 138
 139 extern void channel_reset(struct channel *chan);
 140 extern void lib_ring_buffer_reset(struct lib_ring_buffer *buf);
 141
 142 static inline
 143 unsigned long lib_ring_buffer_get_offset(const struct lib_ring_buffer_config *config,
 144                                          struct lib_ring_buffer *buf)
 145 {
 146         return v_read(config, &buf->offset);
 147 }
 148
 149 static inline
 150 unsigned long lib_ring_buffer_get_consumed(const struct lib_ring_buffer_config *config,
 151                                            struct lib_ring_buffer *buf)
 152 {
 153         return atomic_long_read(&buf->consumed);
 154 }
 155
 156 /*
 157  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 158  * ordering enforced with respect to trace teardown).
 159  */
 160 static inline
 161 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
 162                                  struct lib_ring_buffer *buf)
 163 {
 164         int finalized = ACCESS_ONCE(buf->finalized);
 165         /*
 166          * Read finalized before counters.
 167          */
 168         smp_rmb();
 169         return finalized;
 170 }
 171
 172 static inline
 173 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 174 {
 175         return chan->finalized;
 176 }
 177
 178 static inline
 179 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 180 {
 181         return atomic_read(&chan->record_disabled);
 182 }
 183
 184 static inline
 185 unsigned long lib_ring_buffer_get_read_data_size(
 186                                 const struct lib_ring_buffer_config *config,
 187                                 struct lib_ring_buffer *buf)
 188 {
 189         return subbuffer_get_read_data_size(config, &buf->backend);
 190 }
 191
 192 static inline
 193 unsigned long lib_ring_buffer_get_records_count(
 194                                 const struct lib_ring_buffer_config *config,
 195                                 struct lib_ring_buffer *buf)
 196 {
 197         return v_read(config, &buf->records_count);
 198 }
 199
 200 static inline
 201 unsigned long lib_ring_buffer_get_records_overrun(
 202                                 const struct lib_ring_buffer_config *config,
 203                                 struct lib_ring_buffer *buf)
 204 {
 205         return v_read(config, &buf->records_overrun);
 206 }
 207
 208 static inline
 209 unsigned long lib_ring_buffer_get_records_lost_full(
 210                                 const struct lib_ring_buffer_config *config,
 211                                 struct lib_ring_buffer *buf)
 212 {
 213         return v_read(config, &buf->records_lost_full);
 214 }
 215
 216 static inline
 217 unsigned long lib_ring_buffer_get_records_lost_wrap(
 218                                 const struct lib_ring_buffer_config *config,
 219                                 struct lib_ring_buffer *buf)
 220 {
 221         return v_read(config, &buf->records_lost_wrap);
 222 }
 223
 224 static inline
 225 unsigned long lib_ring_buffer_get_records_lost_big(
 226                                 const struct lib_ring_buffer_config *config,
 227                                 struct lib_ring_buffer *buf)
 228 {
 229         return v_read(config, &buf->records_lost_big);
 230 }
 231
 232 static inline
 233 unsigned long lib_ring_buffer_get_records_read(
 234                                 const struct lib_ring_buffer_config *config,
 235                                 struct lib_ring_buffer *buf)
 236 {
 237         return v_read(config, &buf->backend.records_read);
 238 }
 239
 240 #endif /* _LIB_RING_BUFFER_FRONTEND_H */