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  * priv_data (output) is set to a pointer into a "priv_data_len"-sized
  39  * memory area for client-specific data. This memory is managed by lib
  40  * ring buffer. priv_data_align is the alignment required for the
  41  * private data area.
  42  */
  43
  44 extern
  45 struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
  46                                 const char *name,
  47                                 void **priv_data,
  48                                 size_t priv_data_align,
  49                                 size_t priv_data_size,
  50                                 void *buf_addr,
  51                                 size_t subbuf_size, size_t num_subbuf,
  52                                 unsigned int switch_timer_interval,
  53                                 unsigned int read_timer_interval,
  54                                 int *shm_fd, int *wait_fd,
  55                                 uint64_t *memory_map_size);
  56
  57 /* channel_handle_create - for consumer. */
  58 extern
  59 struct lttng_ust_shm_handle *channel_handle_create(int shm_fd, int wait_fd,
  60                                         uint64_t memory_map_size);
  61
  62 /* channel_handle_add_stream - for consumer. */
  63 extern
  64 int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
  65                 int shm_fd, int wait_fd, uint64_t memory_map_size);
  66
  67 /*
  68  * channel_destroy finalizes all channel's buffers, waits for readers to
  69  * release all references, and destroys the channel.
  70  */
  71 extern
  72 void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
  73                 int shadow);
  74
  75
  76 /* Buffer read operations */
  77
  78 /*
  79  * Iteration on channel cpumask needs to issue a read barrier to match the write
  80  * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu
  81  * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is
  82  * only performed at channel destruction.
  83  */
  84 #define for_each_channel_cpu(cpu, chan)                                 \
  85         for_each_possible_cpu(cpu)
  86
  87 extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
  88                                 const struct lttng_ust_lib_ring_buffer_config *config,
  89                                 struct channel *chan, int cpu,
  90                                 struct lttng_ust_shm_handle *handle,
  91                                 int *shm_fd, int *wait_fd,
  92                                 uint64_t *memory_map_size);
  93 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
  94                                      struct lttng_ust_shm_handle *handle,
  95                                      int shadow);
  96 extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
  97                                          struct lttng_ust_shm_handle *handle,
  98                                          int shadow);
  99
 100 /*
 101  * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer.
 102  */
 103 extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
 104                                     unsigned long *consumed,
 105                                     unsigned long *produced,
 106                                     struct lttng_ust_shm_handle *handle);
 107 extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
 108                                           unsigned long consumed_new,
 109                                           struct lttng_ust_shm_handle *handle);
 110
 111 extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 112                                       unsigned long consumed,
 113                                       struct lttng_ust_shm_handle *handle);
 114 extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 115                                        struct lttng_ust_shm_handle *handle);
 116
 117 /*
 118  * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers
 119  * to read sub-buffers sequentially.
 120  */
 121 static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 122                                                   struct lttng_ust_shm_handle *handle)
 123 {
 124         int ret;
 125
 126         ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot,
 127                                        &buf->prod_snapshot, handle);
 128         if (ret)
 129                 return ret;
 130         ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle);
 131         return ret;
 132 }
 133
 134 static inline
 135 void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf,
 136                                      struct lttng_ust_shm_handle *handle)
 137 {
 138         lib_ring_buffer_put_subbuf(buf, handle);
 139         lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot,
 140                                                         shmp(handle, buf->backend.chan)), handle);
 141 }
 142
 143 extern void channel_reset(struct channel *chan);
 144 extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
 145                                   struct lttng_ust_shm_handle *handle);
 146
 147 static inline
 148 unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config,
 149                                          struct lttng_ust_lib_ring_buffer *buf)
 150 {
 151         return v_read(config, &buf->offset);
 152 }
 153
 154 static inline
 155 unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config,
 156                                            struct lttng_ust_lib_ring_buffer *buf)
 157 {
 158         return uatomic_read(&buf->consumed);
 159 }
 160
 161 /*
 162  * Must call lib_ring_buffer_is_finalized before reading counters (memory
 163  * ordering enforced with respect to trace teardown).
 164  */
 165 static inline
 166 int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config,
 167                                  struct lttng_ust_lib_ring_buffer *buf)
 168 {
 169         int finalized = CMM_ACCESS_ONCE(buf->finalized);
 170         /*
 171          * Read finalized before counters.
 172          */
 173         cmm_smp_rmb();
 174         return finalized;
 175 }
 176
 177 static inline
 178 int lib_ring_buffer_channel_is_finalized(const struct channel *chan)
 179 {
 180         return chan->finalized;
 181 }
 182
 183 static inline
 184 int lib_ring_buffer_channel_is_disabled(const struct channel *chan)
 185 {
 186         return uatomic_read(&chan->record_disabled);
 187 }
 188
 189 static inline
 190 unsigned long lib_ring_buffer_get_read_data_size(
 191                                 const struct lttng_ust_lib_ring_buffer_config *config,
 192                                 struct lttng_ust_lib_ring_buffer *buf,
 193                                 struct lttng_ust_shm_handle *handle)
 194 {
 195         return subbuffer_get_read_data_size(config, &buf->backend, handle);
 196 }
 197
 198 static inline
 199 unsigned long lib_ring_buffer_get_records_count(
 200                                 const struct lttng_ust_lib_ring_buffer_config *config,
 201                                 struct lttng_ust_lib_ring_buffer *buf)
 202 {
 203         return v_read(config, &buf->records_count);
 204 }
 205
 206 static inline
 207 unsigned long lib_ring_buffer_get_records_overrun(
 208                                 const struct lttng_ust_lib_ring_buffer_config *config,
 209                                 struct lttng_ust_lib_ring_buffer *buf)
 210 {
 211         return v_read(config, &buf->records_overrun);
 212 }
 213
 214 static inline
 215 unsigned long lib_ring_buffer_get_records_lost_full(
 216                                 const struct lttng_ust_lib_ring_buffer_config *config,
 217                                 struct lttng_ust_lib_ring_buffer *buf)
 218 {
 219         return v_read(config, &buf->records_lost_full);
 220 }
 221
 222 static inline
 223 unsigned long lib_ring_buffer_get_records_lost_wrap(
 224                                 const struct lttng_ust_lib_ring_buffer_config *config,
 225                                 struct lttng_ust_lib_ring_buffer *buf)
 226 {
 227         return v_read(config, &buf->records_lost_wrap);
 228 }
 229
 230 static inline
 231 unsigned long lib_ring_buffer_get_records_lost_big(
 232                                 const struct lttng_ust_lib_ring_buffer_config *config,
 233                                 struct lttng_ust_lib_ring_buffer *buf)
 234 {
 235         return v_read(config, &buf->records_lost_big);
 236 }
 237
 238 static inline
 239 unsigned long lib_ring_buffer_get_records_read(
 240                                 const struct lttng_ust_lib_ring_buffer_config *config,
 241                                 struct lttng_ust_lib_ring_buffer *buf)
 242 {
 243         return v_read(config, &buf->backend.records_read);
 244 }
 245
 246 #endif /* _LINUX_RING_BUFFER_FRONTEND_H */