| 1 | /* |
| 2 | * SPDX-License-Identifier: MIT |
| 3 | * |
| 4 | * Copyright (C) 2010-2021 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * |
| 6 | * Ring buffer configuration header. Note: after declaring the standard inline |
| 7 | * functions, clients should also include linux/ringbuffer/api.h. |
| 8 | */ |
| 9 | |
| 10 | #ifndef _LTTNG_RING_BUFFER_CONFIG_H |
| 11 | #define _LTTNG_RING_BUFFER_CONFIG_H |
| 12 | |
| 13 | #include <errno.h> |
| 14 | #include <lttng/ust-tracer.h> |
| 15 | #include <stdint.h> |
| 16 | #include <stddef.h> |
| 17 | #include <urcu/arch.h> |
| 18 | #include <string.h> |
| 19 | #include <lttng/align.h> |
| 20 | #include <lttng/ust-compiler.h> |
| 21 | |
| 22 | struct lttng_ust_lib_ring_buffer; |
| 23 | struct lttng_ust_lib_ring_buffer_channel; |
| 24 | struct lttng_ust_lib_ring_buffer_config; |
| 25 | struct lttng_ust_lib_ring_buffer_ctx; |
| 26 | struct lttng_ust_shm_handle; |
| 27 | |
| 28 | /* |
| 29 | * Ring buffer client callbacks. Only used by slow path, never on fast path. |
| 30 | * For the fast path, record_header_size(), ring_buffer_clock_read() should be |
| 31 | * provided as inline functions too. These may simply return 0 if not used by |
| 32 | * the client. |
| 33 | */ |
| 34 | struct lttng_ust_lib_ring_buffer_client_cb { |
| 35 | /* Mandatory callbacks */ |
| 36 | |
| 37 | /* A static inline version is also required for fast path */ |
| 38 | uint64_t (*ring_buffer_clock_read) (struct lttng_ust_lib_ring_buffer_channel *chan); |
| 39 | size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config, |
| 40 | struct lttng_ust_lib_ring_buffer_channel *chan, |
| 41 | size_t offset, |
| 42 | size_t *pre_header_padding, |
| 43 | struct lttng_ust_lib_ring_buffer_ctx *ctx, |
| 44 | void *client_ctx); |
| 45 | |
| 46 | /* Slow path only, at subbuffer switch */ |
| 47 | size_t (*subbuffer_header_size) (void); |
| 48 | void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc, |
| 49 | unsigned int subbuf_idx, |
| 50 | struct lttng_ust_shm_handle *handle); |
| 51 | void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc, |
| 52 | unsigned int subbuf_idx, unsigned long data_size, |
| 53 | struct lttng_ust_shm_handle *handle); |
| 54 | |
| 55 | /* Optional callbacks (can be set to NULL) */ |
| 56 | |
| 57 | /* Called at buffer creation/finalize */ |
| 58 | int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv, |
| 59 | int cpu, const char *name, |
| 60 | struct lttng_ust_shm_handle *handle); |
| 61 | /* |
| 62 | * Clients should guarantee that no new reader handle can be opened |
| 63 | * after finalize. |
| 64 | */ |
| 65 | void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf, |
| 66 | void *priv, int cpu, |
| 67 | struct lttng_ust_shm_handle *handle); |
| 68 | |
| 69 | /* |
| 70 | * Extract header length, payload length and timestamp from event |
| 71 | * record. Used by buffer iterators. Timestamp is only used by channel |
| 72 | * iterator. |
| 73 | */ |
| 74 | void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config, |
| 75 | struct lttng_ust_lib_ring_buffer_channel *chan, |
| 76 | struct lttng_ust_lib_ring_buffer *buf, |
| 77 | size_t offset, size_t *header_len, |
| 78 | size_t *payload_len, uint64_t *timestamp, |
| 79 | struct lttng_ust_shm_handle *handle); |
| 80 | /* |
| 81 | * Offset and size of content size field in client. |
| 82 | */ |
| 83 | void (*content_size_field) (const struct lttng_ust_lib_ring_buffer_config *config, |
| 84 | size_t *offset, size_t *length); |
| 85 | void (*packet_size_field) (const struct lttng_ust_lib_ring_buffer_config *config, |
| 86 | size_t *offset, size_t *length); |
| 87 | }; |
| 88 | |
| 89 | /* |
| 90 | * Ring buffer instance configuration. |
| 91 | * |
| 92 | * Declare as "static const" within the client object to ensure the inline fast |
| 93 | * paths can be optimized. |
| 94 | * |
| 95 | * alloc/sync pairs: |
| 96 | * |
| 97 | * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU : |
| 98 | * Per-cpu buffers with per-cpu synchronization. Tracing must be performed |
| 99 | * with preemption disabled (lib_ring_buffer_get_cpu() and |
| 100 | * lib_ring_buffer_put_cpu()). |
| 101 | * |
| 102 | * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL : |
| 103 | * Per-cpu buffer with global synchronization. Tracing can be performed with |
| 104 | * preemption enabled, statistically stays on the local buffers. |
| 105 | * |
| 106 | * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU : |
| 107 | * Should only be used for buffers belonging to a single thread or protected |
| 108 | * by mutual exclusion by the client. Note that periodical sub-buffer switch |
| 109 | * should be disabled in this kind of configuration. |
| 110 | * |
| 111 | * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL : |
| 112 | * Global shared buffer with global synchronization. |
| 113 | * |
| 114 | * wakeup: |
| 115 | * |
| 116 | * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the |
| 117 | * buffers and wake up readers if data is ready. Mainly useful for tracers which |
| 118 | * don't want to call into the wakeup code on the tracing path. Use in |
| 119 | * combination with "read_timer_interval" channel_create() argument. |
| 120 | * |
| 121 | * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is |
| 122 | * ready to read. Lower latencies before the reader is woken up. Mainly suitable |
| 123 | * for drivers. |
| 124 | * |
| 125 | * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client |
| 126 | * has the responsibility to perform wakeups. |
| 127 | */ |
| 128 | #define LTTNG_UST_RING_BUFFER_CONFIG_PADDING 20 |
| 129 | |
| 130 | enum lttng_ust_lib_ring_buffer_alloc_types { |
| 131 | RING_BUFFER_ALLOC_PER_CPU, |
| 132 | RING_BUFFER_ALLOC_GLOBAL, |
| 133 | }; |
| 134 | |
| 135 | enum lttng_ust_lib_ring_buffer_sync_types { |
| 136 | RING_BUFFER_SYNC_PER_CPU, /* Wait-free */ |
| 137 | RING_BUFFER_SYNC_GLOBAL, /* Lock-free */ |
| 138 | }; |
| 139 | |
| 140 | enum lttng_ust_lib_ring_buffer_mode_types { |
| 141 | RING_BUFFER_OVERWRITE = 0, /* Overwrite when buffer full */ |
| 142 | RING_BUFFER_DISCARD = 1, /* Discard when buffer full */ |
| 143 | }; |
| 144 | |
| 145 | enum lttng_ust_lib_ring_buffer_output_types { |
| 146 | RING_BUFFER_SPLICE, |
| 147 | RING_BUFFER_MMAP, |
| 148 | RING_BUFFER_READ, /* TODO */ |
| 149 | RING_BUFFER_ITERATOR, |
| 150 | RING_BUFFER_NONE, |
| 151 | }; |
| 152 | |
| 153 | enum lttng_ust_lib_ring_buffer_backend_types { |
| 154 | RING_BUFFER_PAGE, |
| 155 | RING_BUFFER_VMAP, /* TODO */ |
| 156 | RING_BUFFER_STATIC, /* TODO */ |
| 157 | }; |
| 158 | |
| 159 | enum lttng_ust_lib_ring_buffer_oops_types { |
| 160 | RING_BUFFER_NO_OOPS_CONSISTENCY, |
| 161 | RING_BUFFER_OOPS_CONSISTENCY, |
| 162 | }; |
| 163 | |
| 164 | enum lttng_ust_lib_ring_buffer_ipi_types { |
| 165 | RING_BUFFER_IPI_BARRIER, |
| 166 | RING_BUFFER_NO_IPI_BARRIER, |
| 167 | }; |
| 168 | |
| 169 | enum lttng_ust_lib_ring_buffer_wakeup_types { |
| 170 | RING_BUFFER_WAKEUP_BY_TIMER, /* wake up performed by timer */ |
| 171 | RING_BUFFER_WAKEUP_BY_WRITER, /* |
| 172 | * writer wakes up reader, |
| 173 | * not lock-free |
| 174 | * (takes spinlock). |
| 175 | */ |
| 176 | }; |
| 177 | |
| 178 | struct lttng_ust_lib_ring_buffer_config { |
| 179 | enum lttng_ust_lib_ring_buffer_alloc_types alloc; |
| 180 | enum lttng_ust_lib_ring_buffer_sync_types sync; |
| 181 | enum lttng_ust_lib_ring_buffer_mode_types mode; |
| 182 | enum lttng_ust_lib_ring_buffer_output_types output; |
| 183 | enum lttng_ust_lib_ring_buffer_backend_types backend; |
| 184 | enum lttng_ust_lib_ring_buffer_oops_types oops; |
| 185 | enum lttng_ust_lib_ring_buffer_ipi_types ipi; |
| 186 | enum lttng_ust_lib_ring_buffer_wakeup_types wakeup; |
| 187 | /* |
| 188 | * tsc_bits: timestamp bits saved at each record. |
| 189 | * 0 and 64 disable the timestamp compression scheme. |
| 190 | */ |
| 191 | unsigned int tsc_bits; |
| 192 | struct lttng_ust_lib_ring_buffer_client_cb cb; |
| 193 | /* |
| 194 | * client_type is used by the consumer process (which is in a |
| 195 | * different address space) to lookup the appropriate client |
| 196 | * callbacks and update the cb pointers. |
| 197 | */ |
| 198 | int client_type; |
| 199 | int _unused1; |
| 200 | const struct lttng_ust_lib_ring_buffer_client_cb *cb_ptr; |
| 201 | char padding[LTTNG_UST_RING_BUFFER_CONFIG_PADDING]; |
| 202 | }; |
| 203 | |
| 204 | /* |
| 205 | * Reservation flags. |
| 206 | * |
| 207 | * RING_BUFFER_RFLAG_FULL_TSC |
| 208 | * |
| 209 | * This flag is passed to record_header_size() and to the primitive used to |
| 210 | * write the record header. It indicates that the full 64-bit time value is |
| 211 | * needed in the record header. If this flag is not set, the record header needs |
| 212 | * only to contain "tsc_bits" bit of time value. |
| 213 | * |
| 214 | * Reservation flags can be added by the client, starting from |
| 215 | * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from |
| 216 | * record_header_size() to lib_ring_buffer_write_record_header(). |
| 217 | */ |
| 218 | #define RING_BUFFER_RFLAG_FULL_TSC (1U << 0) |
| 219 | #define RING_BUFFER_RFLAG_END (1U << 1) |
| 220 | |
| 221 | /* |
| 222 | * lib_ring_buffer_check_config() returns 0 on success. |
| 223 | * Used internally to check for valid configurations at channel creation. |
| 224 | */ |
| 225 | static inline lttng_ust_notrace |
| 226 | int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config, |
| 227 | unsigned int switch_timer_interval, |
| 228 | unsigned int read_timer_interval); |
| 229 | static inline |
| 230 | int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config, |
| 231 | unsigned int switch_timer_interval, |
| 232 | unsigned int read_timer_interval) |
| 233 | { |
| 234 | if (config->alloc == RING_BUFFER_ALLOC_GLOBAL |
| 235 | && config->sync == RING_BUFFER_SYNC_PER_CPU |
| 236 | && switch_timer_interval) |
| 237 | return -EINVAL; |
| 238 | return 0; |
| 239 | } |
| 240 | |
| 241 | #endif /* _LTTNG_RING_BUFFER_CONFIG_H */ |