libringbuffer/frontend_types.h

   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 (types).
   7  *
   8  * See ring_buffer_frontend.c for more information on wait-free algorithms.
   9  */
  10
  11 #ifndef _LTTNG_RING_BUFFER_FRONTEND_TYPES_H
  12 #define _LTTNG_RING_BUFFER_FRONTEND_TYPES_H
  13
  14 #include <stdint.h>
  15 #include <string.h>
  16 #include <time.h>       /* for timer_t */
  17
  18 #include <urcu/list.h>
  19 #include <urcu/uatomic.h>
  20
  21 #include <lttng/ringbuffer-context.h>
  22 #include "ringbuffer-config.h"
  23 #include <usterr-signal-safe.h>
  24 #include "backend_types.h"
  25 #include "shm_internal.h"
  26 #include "shm_types.h"
  27 #include "vatomic.h"
  28
  29 /*
  30  * A switch is done during tracing or as a final flush after tracing (so it
  31  * won't write in the new sub-buffer).
  32  */
  33 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
  34
  35 /* channel: collection of per-cpu ring buffers. */
  36 #define RB_CHANNEL_PADDING              32
  37 struct lttng_ust_lib_ring_buffer_channel {
  38         int record_disabled;
  39         unsigned long commit_count_mask;        /*
  40                                                  * Commit count mask, removing
  41                                                  * the MSBs corresponding to
  42                                                  * bits used to represent the
  43                                                  * subbuffer index.
  44                                                  */
  45
  46         unsigned long switch_timer_interval;    /* Buffer flush (us) */
  47         timer_t switch_timer;
  48         int switch_timer_enabled;
  49
  50         unsigned long read_timer_interval;      /* Reader wakeup (us) */
  51         timer_t read_timer;
  52         int read_timer_enabled;
  53
  54         int finalized;                          /* Has channel been finalized */
  55         size_t priv_data_offset;
  56         unsigned int nr_streams;                /* Number of streams */
  57         struct lttng_ust_shm_handle *handle;
  58         /* Extended options. */
  59         union {
  60                 struct {
  61                         int32_t blocking_timeout_ms;
  62                 } s;
  63                 char padding[RB_CHANNEL_PADDING];
  64         } u;
  65         /*
  66          * Associated backend contains a variable-length array. Needs to
  67          * be last member.
  68          */
  69         struct channel_backend backend;         /* Associated backend */
  70 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  71
  72 /* Per-subbuffer commit counters used on the hot path */
  73 #define RB_COMMIT_COUNT_HOT_PADDING     16
  74 struct commit_counters_hot {
  75         union v_atomic cc;              /* Commit counter */
  76         union v_atomic seq;             /* Consecutive commits */
  77         char padding[RB_COMMIT_COUNT_HOT_PADDING];
  78 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  79
  80 /* Per-subbuffer commit counters used only on cold paths */
  81 #define RB_COMMIT_COUNT_COLD_PADDING    24
  82 struct commit_counters_cold {
  83         union v_atomic cc_sb;           /* Incremented _once_ at sb switch */
  84         char padding[RB_COMMIT_COUNT_COLD_PADDING];
  85 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  86
  87 /* ring buffer state */
  88 #define RB_CRASH_DUMP_ABI_LEN           256
  89 #define RB_RING_BUFFER_PADDING          60
  90
  91 #define RB_CRASH_DUMP_ABI_MAGIC_LEN     16
  92
  93 /*
  94  * The 128-bit magic number is xor'd in the process data so it does not
  95  * cause a false positive when searching for buffers by scanning memory.
  96  * The actual magic number is:
  97  *   0x17, 0x7B, 0xF1, 0x77, 0xBF, 0x17, 0x7B, 0xF1,
  98  *   0x77, 0xBF, 0x17, 0x7B, 0xF1, 0x77, 0xBF, 0x17,
  99  */
 100 #define RB_CRASH_DUMP_ABI_MAGIC_XOR                                     \
 101         {                                                               \
 102                 0x17 ^ 0xFF, 0x7B ^ 0xFF, 0xF1 ^ 0xFF, 0x77 ^ 0xFF,     \
 103                 0xBF ^ 0xFF, 0x17 ^ 0xFF, 0x7B ^ 0xFF, 0xF1 ^ 0xFF,     \
 104                 0x77 ^ 0xFF, 0xBF ^ 0xFF, 0x17 ^ 0xFF, 0x7B ^ 0xFF,     \
 105                 0xF1 ^ 0xFF, 0x77 ^ 0xFF, 0xBF ^ 0xFF, 0x17 ^ 0xFF,     \
 106         }
 107
 108 #define RB_CRASH_ENDIAN                 0x1234
 109
 110 #define RB_CRASH_DUMP_ABI_MAJOR         0
 111 #define RB_CRASH_DUMP_ABI_MINOR         0
 112
 113 enum lttng_crash_type {
 114         LTTNG_CRASH_TYPE_UST = 0,
 115         LTTNG_CRASH_TYPE_KERNEL = 1,
 116 };
 117
 118 struct lttng_crash_abi {
 119         uint8_t magic[RB_CRASH_DUMP_ABI_MAGIC_LEN];
 120         uint64_t mmap_length;   /* Overall lenght of crash record */
 121         uint16_t endian;        /*
 122                                  * { 0x12, 0x34 }: big endian
 123                                  * { 0x34, 0x12 }: little endian
 124                                  */
 125         uint16_t major;         /* Major number. */
 126         uint16_t minor;         /* Minor number. */
 127         uint8_t word_size;      /* Word size (bytes). */
 128         uint8_t layout_type;    /* enum lttng_crash_type */
 129
 130         struct {
 131                 uint32_t prod_offset;
 132                 uint32_t consumed_offset;
 133                 uint32_t commit_hot_array;
 134                 uint32_t commit_hot_seq;
 135                 uint32_t buf_wsb_array;
 136                 uint32_t buf_wsb_id;
 137                 uint32_t sb_array;
 138                 uint32_t sb_array_shmp_offset;
 139                 uint32_t sb_backend_p_offset;
 140                 uint32_t content_size;
 141                 uint32_t packet_size;
 142         } __attribute__((packed)) offset;
 143         struct {
 144                 uint8_t prod_offset;
 145                 uint8_t consumed_offset;
 146                 uint8_t commit_hot_seq;
 147                 uint8_t buf_wsb_id;
 148                 uint8_t sb_array_shmp_offset;
 149                 uint8_t sb_backend_p_offset;
 150                 uint8_t content_size;
 151                 uint8_t packet_size;
 152         } __attribute__((packed)) length;
 153         struct {
 154                 uint32_t commit_hot_array;
 155                 uint32_t buf_wsb_array;
 156                 uint32_t sb_array;
 157         } __attribute__((packed)) stride;
 158
 159         uint64_t buf_size;      /* Size of the buffer */
 160         uint64_t subbuf_size;   /* Sub-buffer size */
 161         uint64_t num_subbuf;    /* Number of sub-buffers for writer */
 162         uint32_t mode;          /* Buffer mode: 0: overwrite, 1: discard */
 163 } __attribute__((packed));
 164
 165 struct lttng_ust_lib_ring_buffer {
 166         /* First 32 bytes are for the buffer crash dump ABI */
 167         struct lttng_crash_abi crash_abi;
 168
 169         /* 32 bytes cache-hot cacheline */
 170         union v_atomic __attribute__((aligned(32))) offset;
 171                                         /* Current offset in the buffer */
 172         DECLARE_SHMP(struct commit_counters_hot, commit_hot);
 173                                         /* Commit count per sub-buffer */
 174         long consumed;                  /*
 175                                          * Current offset in the buffer
 176                                          * standard atomic access (shared)
 177                                          */
 178         int record_disabled;
 179         /* End of cache-hot 32 bytes cacheline */
 180
 181         union v_atomic last_tsc;        /*
 182                                          * Last timestamp written in the buffer.
 183                                          */
 184
 185         struct lttng_ust_lib_ring_buffer_backend backend;
 186                                         /* Associated backend */
 187
 188         DECLARE_SHMP(struct commit_counters_cold, commit_cold);
 189                                         /* Commit count per sub-buffer */
 190         DECLARE_SHMP(uint64_t, ts_end); /*
 191                                          * timestamp_end per sub-buffer.
 192                                          * Time is sampled by the
 193                                          * switch_*_end() callbacks
 194                                          * which are the last space
 195                                          * reservation performed in the
 196                                          * sub-buffer before it can be
 197                                          * fully committed and
 198                                          * delivered. This time value is
 199                                          * then read by the deliver
 200                                          * callback, performed by the
 201                                          * last commit before the buffer
 202                                          * becomes readable.
 203                                          */
 204         long active_readers;            /*
 205                                          * Active readers count
 206                                          * standard atomic access (shared)
 207                                          */
 208                                         /* Dropped records */
 209         union v_atomic records_lost_full;       /* Buffer full */
 210         union v_atomic records_lost_wrap;       /* Nested wrap-around */
 211         union v_atomic records_lost_big;        /* Events too big */
 212         union v_atomic records_count;   /* Number of records written */
 213         union v_atomic records_overrun; /* Number of overwritten records */
 214         //wait_queue_head_t read_wait;  /* reader buffer-level wait queue */
 215         int finalized;                  /* buffer has been finalized */
 216         unsigned long get_subbuf_consumed;      /* Read-side consumed */
 217         unsigned long prod_snapshot;    /* Producer count snapshot */
 218         unsigned long cons_snapshot;    /* Consumer count snapshot */
 219         unsigned int get_subbuf:1;      /* Sub-buffer being held by reader */
 220         /* shmp pointer to self */
 221         DECLARE_SHMP(struct lttng_ust_lib_ring_buffer, self);
 222         char padding[RB_RING_BUFFER_PADDING];
 223 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 224
 225 static inline
 226 void *channel_get_private(struct lttng_ust_lib_ring_buffer_channel *chan)
 227 {
 228         return ((char *) chan) + chan->priv_data_offset;
 229 }
 230
 231 #ifndef __rb_same_type
 232 #define __rb_same_type(a, b)    __builtin_types_compatible_p(typeof(a), typeof(b))
 233 #endif
 234
 235 /*
 236  * Issue warnings and disable channels upon internal error.
 237  * Can receive struct lttng_ust_lib_ring_buffer or struct lttng_ust_lib_ring_buffer_backend
 238  * parameters.
 239  */
 240 #define CHAN_WARN_ON(c, cond)                                           \
 241         ({                                                              \
 242                 struct lttng_ust_lib_ring_buffer_channel *__chan;       \
 243                 int _____ret = caa_unlikely(cond);                              \
 244                 if (_____ret) {                                         \
 245                         if (__rb_same_type(*(c), struct channel_backend))       \
 246                                 __chan = caa_container_of((void *) (c), \
 247                                         struct lttng_ust_lib_ring_buffer_channel, \
 248                                         backend);                       \
 249                         else if (__rb_same_type(*(c),                   \
 250                                         struct lttng_ust_lib_ring_buffer_channel)) \
 251                                 __chan = (void *) (c);                  \
 252                         else                                            \
 253                                 BUG_ON(1);                              \
 254                         uatomic_inc(&__chan->record_disabled);          \
 255                         WARN_ON(1);                                     \
 256                 }                                                       \
 257                 _____ret = _____ret; /* For clang "unused result". */   \
 258         })
 259
 260 #endif /* _LTTNG_RING_BUFFER_FRONTEND_TYPES_H */