| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * |
| 6 | * Ring Buffer Library Synchronization Header (API). |
| 7 | * |
| 8 | * See ring_buffer_frontend.c for more information on wait-free algorithms. |
| 9 | */ |
| 10 | |
| 11 | #ifndef _LTTNG_RING_BUFFER_FRONTEND_H |
| 12 | #define _LTTNG_RING_BUFFER_FRONTEND_H |
| 13 | |
| 14 | #include <stddef.h> |
| 15 | #include <stdint.h> |
| 16 | |
| 17 | #include <urcu/compiler.h> |
| 18 | #include <urcu/uatomic.h> |
| 19 | |
| 20 | #include "smp.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 | * priv_data (output) is set to a pointer into a "priv_data_len"-sized |
| 38 | * memory area for client-specific data. This memory is managed by lib |
| 39 | * ring buffer. priv_data_align is the alignment required for the |
| 40 | * private data area. |
| 41 | */ |
| 42 | |
| 43 | __attribute__((visibility("hidden"))) |
| 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 *priv_data_init, |
| 51 | void *buf_addr, |
| 52 | size_t subbuf_size, size_t num_subbuf, |
| 53 | unsigned int switch_timer_interval, |
| 54 | unsigned int read_timer_interval, |
| 55 | const int *stream_fds, int nr_stream_fds, |
| 56 | int64_t blocking_timeout); |
| 57 | |
| 58 | /* |
| 59 | * channel_destroy finalizes all channel's buffers, waits for readers to |
| 60 | * release all references, and destroys the channel. |
| 61 | */ |
| 62 | __attribute__((visibility("hidden"))) |
| 63 | extern |
| 64 | void channel_destroy(struct lttng_ust_lib_ring_buffer_channel *chan, |
| 65 | struct lttng_ust_shm_handle *handle, |
| 66 | int consumer); |
| 67 | |
| 68 | |
| 69 | /* Buffer read operations */ |
| 70 | |
| 71 | /* |
| 72 | * Iteration on channel cpumask needs to issue a read barrier to match the write |
| 73 | * barrier in cpu hotplug. It orders the cpumask read before read of per-cpu |
| 74 | * buffer data. The per-cpu buffer is never removed by cpu hotplug; teardown is |
| 75 | * only performed at channel destruction. |
| 76 | */ |
| 77 | #define for_each_channel_cpu(cpu, chan) \ |
| 78 | for_each_possible_cpu(cpu) |
| 79 | |
| 80 | __attribute__((visibility("hidden"))) |
| 81 | extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer( |
| 82 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 83 | struct lttng_ust_lib_ring_buffer_channel *chan, int cpu, |
| 84 | struct lttng_ust_shm_handle *handle, |
| 85 | int *shm_fd, int *wait_fd, |
| 86 | int *wakeup_fd, |
| 87 | uint64_t *memory_map_size); |
| 88 | |
| 89 | __attribute__((visibility("hidden"))) |
| 90 | extern |
| 91 | int ring_buffer_channel_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config, |
| 92 | struct lttng_ust_lib_ring_buffer_channel *chan, |
| 93 | struct lttng_ust_shm_handle *handle); |
| 94 | |
| 95 | __attribute__((visibility("hidden"))) |
| 96 | extern |
| 97 | int ring_buffer_channel_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config, |
| 98 | struct lttng_ust_lib_ring_buffer_channel *chan, |
| 99 | struct lttng_ust_shm_handle *handle); |
| 100 | |
| 101 | __attribute__((visibility("hidden"))) |
| 102 | extern |
| 103 | int ring_buffer_stream_close_wait_fd(const struct lttng_ust_lib_ring_buffer_config *config, |
| 104 | struct lttng_ust_lib_ring_buffer_channel *chan, |
| 105 | struct lttng_ust_shm_handle *handle, |
| 106 | int cpu); |
| 107 | |
| 108 | __attribute__((visibility("hidden"))) |
| 109 | extern |
| 110 | int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_lib_ring_buffer_config *config, |
| 111 | struct lttng_ust_lib_ring_buffer_channel *chan, |
| 112 | struct lttng_ust_shm_handle *handle, |
| 113 | int cpu); |
| 114 | |
| 115 | __attribute__((visibility("hidden"))) |
| 116 | extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf, |
| 117 | struct lttng_ust_shm_handle *handle); |
| 118 | |
| 119 | __attribute__((visibility("hidden"))) |
| 120 | extern void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf, |
| 121 | struct lttng_ust_shm_handle *handle); |
| 122 | |
| 123 | /* |
| 124 | * Initialize signals for ring buffer. Should be called early e.g. by |
| 125 | * main() in the program to affect all threads. |
| 126 | */ |
| 127 | __attribute__((visibility("hidden"))) |
| 128 | void lib_ringbuffer_signal_init(void); |
| 129 | |
| 130 | /* |
| 131 | * Read sequence: snapshot, many get_subbuf/put_subbuf, move_consumer. |
| 132 | */ |
| 133 | __attribute__((visibility("hidden"))) |
| 134 | extern int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf, |
| 135 | unsigned long *consumed, |
| 136 | unsigned long *produced, |
| 137 | struct lttng_ust_shm_handle *handle); |
| 138 | |
| 139 | __attribute__((visibility("hidden"))) |
| 140 | extern int lib_ring_buffer_snapshot_sample_positions( |
| 141 | struct lttng_ust_lib_ring_buffer *buf, |
| 142 | unsigned long *consumed, |
| 143 | unsigned long *produced, |
| 144 | struct lttng_ust_shm_handle *handle); |
| 145 | |
| 146 | __attribute__((visibility("hidden"))) |
| 147 | extern void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf, |
| 148 | unsigned long consumed_new, |
| 149 | struct lttng_ust_shm_handle *handle); |
| 150 | |
| 151 | __attribute__((visibility("hidden"))) |
| 152 | extern int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf, |
| 153 | unsigned long consumed, |
| 154 | struct lttng_ust_shm_handle *handle); |
| 155 | __attribute__((visibility("hidden"))) |
| 156 | extern void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf, |
| 157 | struct lttng_ust_shm_handle *handle); |
| 158 | |
| 159 | /* |
| 160 | * lib_ring_buffer_get_next_subbuf/lib_ring_buffer_put_next_subbuf are helpers |
| 161 | * to read sub-buffers sequentially. |
| 162 | */ |
| 163 | static inline int lib_ring_buffer_get_next_subbuf(struct lttng_ust_lib_ring_buffer *buf, |
| 164 | struct lttng_ust_shm_handle *handle) |
| 165 | { |
| 166 | int ret; |
| 167 | |
| 168 | ret = lib_ring_buffer_snapshot(buf, &buf->cons_snapshot, |
| 169 | &buf->prod_snapshot, handle); |
| 170 | if (ret) |
| 171 | return ret; |
| 172 | ret = lib_ring_buffer_get_subbuf(buf, buf->cons_snapshot, handle); |
| 173 | return ret; |
| 174 | } |
| 175 | |
| 176 | static inline |
| 177 | void lib_ring_buffer_put_next_subbuf(struct lttng_ust_lib_ring_buffer *buf, |
| 178 | struct lttng_ust_shm_handle *handle) |
| 179 | { |
| 180 | struct lttng_ust_lib_ring_buffer_channel *chan; |
| 181 | |
| 182 | chan = shmp(handle, buf->backend.chan); |
| 183 | if (!chan) |
| 184 | return; |
| 185 | lib_ring_buffer_put_subbuf(buf, handle); |
| 186 | lib_ring_buffer_move_consumer(buf, subbuf_align(buf->cons_snapshot, chan), |
| 187 | handle); |
| 188 | } |
| 189 | |
| 190 | __attribute__((visibility("hidden"))) |
| 191 | extern void channel_reset(struct lttng_ust_lib_ring_buffer_channel *chan); |
| 192 | |
| 193 | __attribute__((visibility("hidden"))) |
| 194 | extern void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf, |
| 195 | struct lttng_ust_shm_handle *handle); |
| 196 | |
| 197 | static inline |
| 198 | unsigned long lib_ring_buffer_get_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
| 199 | struct lttng_ust_lib_ring_buffer *buf) |
| 200 | { |
| 201 | return v_read(config, &buf->offset); |
| 202 | } |
| 203 | |
| 204 | static inline |
| 205 | unsigned long lib_ring_buffer_get_consumed(const struct lttng_ust_lib_ring_buffer_config *config, |
| 206 | struct lttng_ust_lib_ring_buffer *buf) |
| 207 | { |
| 208 | return uatomic_read(&buf->consumed); |
| 209 | } |
| 210 | |
| 211 | /* |
| 212 | * Must call lib_ring_buffer_is_finalized before reading counters (memory |
| 213 | * ordering enforced with respect to trace teardown). |
| 214 | */ |
| 215 | static inline |
| 216 | int lib_ring_buffer_is_finalized(const struct lttng_ust_lib_ring_buffer_config *config, |
| 217 | struct lttng_ust_lib_ring_buffer *buf) |
| 218 | { |
| 219 | int finalized = CMM_ACCESS_ONCE(buf->finalized); |
| 220 | /* |
| 221 | * Read finalized before counters. |
| 222 | */ |
| 223 | cmm_smp_rmb(); |
| 224 | return finalized; |
| 225 | } |
| 226 | |
| 227 | static inline |
| 228 | int lib_ring_buffer_channel_is_finalized(const struct lttng_ust_lib_ring_buffer_channel *chan) |
| 229 | { |
| 230 | return chan->finalized; |
| 231 | } |
| 232 | |
| 233 | static inline |
| 234 | int lib_ring_buffer_channel_is_disabled(const struct lttng_ust_lib_ring_buffer_channel *chan) |
| 235 | { |
| 236 | return uatomic_read(&chan->record_disabled); |
| 237 | } |
| 238 | |
| 239 | static inline |
| 240 | unsigned long lib_ring_buffer_get_read_data_size( |
| 241 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 242 | struct lttng_ust_lib_ring_buffer *buf, |
| 243 | struct lttng_ust_shm_handle *handle) |
| 244 | { |
| 245 | return subbuffer_get_read_data_size(config, &buf->backend, handle); |
| 246 | } |
| 247 | |
| 248 | static inline |
| 249 | unsigned long lib_ring_buffer_get_records_count( |
| 250 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 251 | struct lttng_ust_lib_ring_buffer *buf) |
| 252 | { |
| 253 | return v_read(config, &buf->records_count); |
| 254 | } |
| 255 | |
| 256 | static inline |
| 257 | unsigned long lib_ring_buffer_get_records_overrun( |
| 258 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 259 | struct lttng_ust_lib_ring_buffer *buf) |
| 260 | { |
| 261 | return v_read(config, &buf->records_overrun); |
| 262 | } |
| 263 | |
| 264 | static inline |
| 265 | unsigned long lib_ring_buffer_get_records_lost_full( |
| 266 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 267 | struct lttng_ust_lib_ring_buffer *buf) |
| 268 | { |
| 269 | return v_read(config, &buf->records_lost_full); |
| 270 | } |
| 271 | |
| 272 | static inline |
| 273 | unsigned long lib_ring_buffer_get_records_lost_wrap( |
| 274 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 275 | struct lttng_ust_lib_ring_buffer *buf) |
| 276 | { |
| 277 | return v_read(config, &buf->records_lost_wrap); |
| 278 | } |
| 279 | |
| 280 | static inline |
| 281 | unsigned long lib_ring_buffer_get_records_lost_big( |
| 282 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 283 | struct lttng_ust_lib_ring_buffer *buf) |
| 284 | { |
| 285 | return v_read(config, &buf->records_lost_big); |
| 286 | } |
| 287 | |
| 288 | static inline |
| 289 | unsigned long lib_ring_buffer_get_records_read( |
| 290 | const struct lttng_ust_lib_ring_buffer_config *config, |
| 291 | struct lttng_ust_lib_ring_buffer *buf) |
| 292 | { |
| 293 | return v_read(config, &buf->backend.records_read); |
| 294 | } |
| 295 | |
| 296 | #endif /* _LTTNG_RING_BUFFER_FRONTEND_H */ |