include/ringbuffer/config.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * ringbuffer/config.h
   4  *
   5  * Ring buffer configuration header. Note: after declaring the standard inline
   6  * functions, clients should also include linux/ringbuffer/api.h.
   7  *
   8  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  */
  10
  11 #ifndef _LIB_RING_BUFFER_CONFIG_H
  12 #define _LIB_RING_BUFFER_CONFIG_H
  13
  14 #include <linux/types.h>
  15 #include <linux/percpu.h>
  16 #include <lttng/align.h>
  17 #include <lttng/tracer-core.h>
  18
  19 struct lttng_kernel_ring_buffer;
  20 struct lttng_kernel_ring_buffer_channel;
  21 struct lttng_kernel_ring_buffer_config;
  22 struct lttng_kernel_ring_buffer_ctx;
  23 struct lttng_kernel_ring_buffer_ctx_private;
  24
  25 /*
  26  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  27  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  28  * provided as inline functions too.  These may simply return 0 if not used by
  29  * the client.
  30  */
  31 struct lttng_kernel_ring_buffer_client_cb {
  32         /* Mandatory callbacks */
  33
  34         /* A static inline version is also required for fast path */
  35         u64 (*ring_buffer_clock_read) (struct lttng_kernel_ring_buffer_channel *chan);
  36         size_t (*record_header_size) (const struct lttng_kernel_ring_buffer_config *config,
  37                                       struct lttng_kernel_ring_buffer_channel *chan, size_t offset,
  38                                       size_t *pre_header_padding,
  39                                       struct lttng_kernel_ring_buffer_ctx *ctx,
  40                                       void *client_ctx);
  41
  42         /* Slow path only, at subbuffer switch */
  43         size_t (*subbuffer_header_size) (void);
  44         void (*buffer_begin) (struct lttng_kernel_ring_buffer *buf, u64 tsc,
  45                               unsigned int subbuf_idx);
  46         void (*buffer_end) (struct lttng_kernel_ring_buffer *buf, u64 tsc,
  47                             unsigned int subbuf_idx, unsigned long data_size,
  48                             const struct lttng_kernel_ring_buffer_ctx *ctx);
  49
  50         /* Optional callbacks (can be set to NULL) */
  51
  52         /* Called at buffer creation/finalize */
  53         int (*buffer_create) (struct lttng_kernel_ring_buffer *buf, void *priv,
  54                               int cpu, const char *name);
  55         /*
  56          * Clients should guarantee that no new reader handle can be opened
  57          * after finalize.
  58          */
  59         void (*buffer_finalize) (struct lttng_kernel_ring_buffer *buf, void *priv, int cpu);
  60
  61         /*
  62          * Extract header length, payload length and timestamp from event
  63          * record. Used by buffer iterators. Timestamp is only used by channel
  64          * iterator.
  65          */
  66         void (*record_get) (const struct lttng_kernel_ring_buffer_config *config,
  67                             struct lttng_kernel_ring_buffer_channel *chan, struct lttng_kernel_ring_buffer *buf,
  68                             size_t offset, size_t *header_len,
  69                             size_t *payload_len, u64 *timestamp);
  70 };
  71
  72 /*
  73  * Ring buffer instance configuration.
  74  *
  75  * Declare as "static const" within the client object to ensure the inline fast
  76  * paths can be optimized.
  77  *
  78  * alloc/sync pairs:
  79  *
  80  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  81  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  82  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  83  *   lib_ring_buffer_put_cpu()).
  84  *
  85  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
  86  *   Per-cpu buffer with global synchronization. Tracing can be performed with
  87  *   preemption enabled, statistically stays on the local buffers.
  88  *
  89  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
  90  *   Should only be used for buffers belonging to a single thread or protected
  91  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
  92  *   should be disabled in this kind of configuration.
  93  *
  94  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
  95  *   Global shared buffer with global synchronization.
  96  *
  97  * wakeup:
  98  *
  99  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the
 100  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 101  * don't want to call into the wakeup code on the tracing path. Use in
 102  * combination with "read_timer_interval" channel_create() argument.
 103  *
 104  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 105  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 106  * for drivers. Going through an "irq_work" allows triggering this type of wakeup
 107  * even from NMI context: the wakeup will be slightly delayed until the next
 108  * interrupts are handled.
 109  *
 110  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 111  * has the responsibility to perform wakeups.
 112  */
 113 struct lttng_kernel_ring_buffer_config {
 114         enum {
 115                 RING_BUFFER_ALLOC_PER_CPU,
 116                 RING_BUFFER_ALLOC_GLOBAL,
 117         } alloc;
 118         enum {
 119                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 120                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 121         } sync;
 122         enum {
 123                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 124                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 125         } mode;
 126         enum {
 127                 RING_BUFFER_SPLICE,
 128                 RING_BUFFER_MMAP,
 129                 RING_BUFFER_READ,               /* TODO */
 130                 RING_BUFFER_ITERATOR,
 131                 RING_BUFFER_NONE,
 132         } output;
 133         enum {
 134                 RING_BUFFER_PAGE,
 135                 RING_BUFFER_VMAP,               /* TODO */
 136                 RING_BUFFER_STATIC,             /* TODO */
 137         } backend;
 138         enum {
 139                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 140                 RING_BUFFER_OOPS_CONSISTENCY,
 141         } oops;
 142         enum {
 143                 RING_BUFFER_IPI_BARRIER,
 144                 RING_BUFFER_NO_IPI_BARRIER,
 145         } ipi;
 146         enum {
 147                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 148                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 149                                                  * writer wakes up reader through
 150                                                  * irq_work.
 151                                                  */
 152         } wakeup;
 153         /*
 154          * tsc_bits: timestamp bits saved at each record.
 155          *   0 and 64 disable the timestamp compression scheme.
 156          */
 157         unsigned int tsc_bits;
 158         struct lttng_kernel_ring_buffer_client_cb cb;
 159 };
 160
 161 /*
 162  * ring buffer private context
 163  *
 164  * Private context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 165  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 166  * lib_ring_buffer_write().
 167  *
 168  * Get struct lttng_kernel_ring_buffer_ctx parent with container_of().
 169  */
 170
 171 struct lttng_kernel_ring_buffer_ctx_private {
 172         /* input received by lib_ring_buffer_reserve(). */
 173         struct lttng_kernel_ring_buffer_channel *chan;                  /* ring buffer channel */
 174
 175         /* output from lib_ring_buffer_reserve() */
 176         int reserve_cpu;                        /* processor id updated by the reserve */
 177         size_t slot_size;                       /* size of the reserved slot */
 178         unsigned long buf_offset;               /* offset following the record header */
 179         unsigned long pre_offset;               /*
 180                                                  * Initial offset position _before_
 181                                                  * the record is written. Positioned
 182                                                  * prior to record header alignment
 183                                                  * padding.
 184                                                  */
 185         u64 tsc;                                /* time-stamp counter value */
 186         unsigned int rflags;                    /* reservation flags */
 187
 188         struct lttng_kernel_ring_buffer *buf;   /*
 189                                                  * buffer corresponding to processor id
 190                                                  * for this channel
 191                                                  */
 192         struct lttng_kernel_ring_buffer_backend_pages *backend_pages;
 193
 194         /*
 195          * Records lost counts are only loaded into these fields before
 196          * reserving the last bytes from the ring buffer.
 197          */
 198         unsigned long records_lost_full;
 199         unsigned long records_lost_wrap;
 200         unsigned long records_lost_big;
 201 };
 202
 203 /*
 204  * ring buffer context
 205  *
 206  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 207  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 208  * lib_ring_buffer_write().
 209  */
 210 struct lttng_kernel_ring_buffer_ctx {
 211         /* Private ring buffer context, set by reserve callback. */
 212         struct lttng_kernel_ring_buffer_ctx_private priv;
 213
 214         /* input received by lib_ring_buffer_reserve(), saved here. */
 215         void *client_priv;              /* Ring buffer client private data */
 216
 217         size_t data_size;               /* size of payload */
 218         int largest_align;              /*
 219                                          * alignment of the largest element
 220                                          * in the payload
 221                                          */
 222         struct lttng_kernel_probe_ctx *probe_ctx;       /* Probe context */
 223 };
 224
 225 /**
 226  * lib_ring_buffer_ctx_init - initialize ring buffer context
 227  * @ctx: ring buffer context to initialize
 228  * @client_priv: client private data
 229  * @data_size: size of record data payload. It must be greater than 0.
 230  * @largest_align: largest alignment within data payload types
 231  */
 232 static inline
 233 void lib_ring_buffer_ctx_init(struct lttng_kernel_ring_buffer_ctx *ctx,
 234                               void *client_priv,
 235                               size_t data_size, int largest_align,
 236                               struct lttng_kernel_probe_ctx *probe_ctx)
 237 {
 238         ctx->client_priv = client_priv;
 239         ctx->data_size = data_size;
 240         ctx->largest_align = largest_align;
 241         ctx->probe_ctx = probe_ctx;
 242 }
 243
 244 /*
 245  * Reservation flags.
 246  *
 247  * RING_BUFFER_RFLAG_FULL_TSC
 248  *
 249  * This flag is passed to record_header_size() and to the primitive used to
 250  * write the record header. It indicates that the full 64-bit time value is
 251  * needed in the record header. If this flag is not set, the record header needs
 252  * only to contain "tsc_bits" bit of time value.
 253  *
 254  * Reservation flags can be added by the client, starting from
 255  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 256  * record_header_size() to lib_ring_buffer_write_record_header().
 257  */
 258 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 259 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 260
 261 #ifndef LTTNG_TRACER_CORE_H
 262 #error "lttng/tracer-core.h is needed for RING_BUFFER_ALIGN define"
 263 #endif
 264
 265 /*
 266  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 267  * compile-time. We have to duplicate the "config->align" information and the
 268  * definition here because config->align is used both in the slow and fast
 269  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 270  */
 271 #ifdef RING_BUFFER_ALIGN
 272
 273 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 274
 275 /*
 276  * Calculate the offset needed to align the type.
 277  * size_of_type must be non-zero.
 278  */
 279 static inline
 280 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 281 {
 282         return offset_align(align_drift, size_of_type);
 283 }
 284
 285 #else
 286
 287 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 288
 289 /*
 290  * Calculate the offset needed to align the type.
 291  * size_of_type must be non-zero.
 292  */
 293 static inline
 294 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 295 {
 296         return 0;
 297 }
 298
 299 #endif
 300
 301 /**
 302  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 303  * @ctx: ring buffer context.
 304  */
 305 static inline
 306 void lib_ring_buffer_align_ctx(struct lttng_kernel_ring_buffer_ctx *ctx,
 307                            size_t alignment)
 308 {
 309         ctx->priv.buf_offset += lib_ring_buffer_align(ctx->priv.buf_offset,
 310                                                  alignment);
 311 }
 312
 313 /*
 314  * lib_ring_buffer_check_config() returns 0 on success.
 315  * Used internally to check for valid configurations at channel creation.
 316  */
 317 static inline
 318 int lib_ring_buffer_check_config(const struct lttng_kernel_ring_buffer_config *config,
 319                              unsigned int switch_timer_interval,
 320                              unsigned int read_timer_interval)
 321 {
 322         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 323             && config->sync == RING_BUFFER_SYNC_PER_CPU
 324             && switch_timer_interval)
 325                 return -EINVAL;
 326         return 0;
 327 }
 328
 329 #include <ringbuffer/vatomic.h>
 330
 331 #endif /* _LIB_RING_BUFFER_CONFIG_H */