libringbuffer/frontend_types.h

   1 #ifndef _LTTNG_RING_BUFFER_FRONTEND_TYPES_H
   2 #define _LTTNG_RING_BUFFER_FRONTEND_TYPES_H
   3
   4 /*
   5  * libringbuffer/frontend_types.h
   6  *
   7  * Ring Buffer Library Synchronization Header (types).
   8  *
   9  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; only
  14  * version 2.1 of the License.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  24  *
  25  * Author:
  26  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  27  *
  28  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  29  */
  30
  31 #include <string.h>
  32 #include <time.h>       /* for timer_t */
  33
  34 #include <urcu/list.h>
  35 #include <urcu/uatomic.h>
  36
  37 #include <lttng/ringbuffer-config.h>
  38 #include <usterr-signal-safe.h>
  39 #include "backend_types.h"
  40 #include "shm_internal.h"
  41 #include "shm_types.h"
  42 #include "vatomic.h"
  43
  44 /*
  45  * A switch is done during tracing or as a final flush after tracing (so it
  46  * won't write in the new sub-buffer).
  47  */
  48 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
  49
  50 /* channel: collection of per-cpu ring buffers. */
  51 #define RB_CHANNEL_PADDING              32
  52 struct channel {
  53         int record_disabled;
  54         unsigned long commit_count_mask;        /*
  55                                                  * Commit count mask, removing
  56                                                  * the MSBs corresponding to
  57                                                  * bits used to represent the
  58                                                  * subbuffer index.
  59                                                  */
  60
  61         unsigned long switch_timer_interval;    /* Buffer flush (us) */
  62         timer_t switch_timer;
  63         int switch_timer_enabled;
  64
  65         unsigned long read_timer_interval;      /* Reader wakeup (us) */
  66         timer_t read_timer;
  67         int read_timer_enabled;
  68
  69         int finalized;                          /* Has channel been finalized */
  70         size_t priv_data_offset;
  71         unsigned int nr_streams;                /* Number of streams */
  72         struct lttng_ust_shm_handle *handle;
  73         char padding[RB_CHANNEL_PADDING];
  74         /*
  75          * Associated backend contains a variable-length array. Needs to
  76          * be last member.
  77          */
  78         struct channel_backend backend;         /* Associated backend */
  79 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  80
  81 /* Per-subbuffer commit counters used on the hot path */
  82 #define RB_COMMIT_COUNT_HOT_PADDING     16
  83 struct commit_counters_hot {
  84         union v_atomic cc;              /* Commit counter */
  85         union v_atomic seq;             /* Consecutive commits */
  86         char padding[RB_COMMIT_COUNT_HOT_PADDING];
  87 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  88
  89 /* Per-subbuffer commit counters used only on cold paths */
  90 #define RB_COMMIT_COUNT_COLD_PADDING    24
  91 struct commit_counters_cold {
  92         union v_atomic cc_sb;           /* Incremented _once_ at sb switch */
  93         char padding[RB_COMMIT_COUNT_COLD_PADDING];
  94 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  95
  96 /* ring buffer state */
  97 #define RB_RING_BUFFER_PADDING          64
  98 struct lttng_ust_lib_ring_buffer {
  99         /* First 32 bytes cache-hot cacheline */
 100         union v_atomic offset;          /* Current offset in the buffer */
 101         DECLARE_SHMP(struct commit_counters_hot, commit_hot);
 102                                         /* Commit count per sub-buffer */
 103         long consumed;                  /*
 104                                          * Current offset in the buffer
 105                                          * standard atomic access (shared)
 106                                          */
 107         int record_disabled;
 108         /* End of first 32 bytes cacheline */
 109         union v_atomic last_tsc;        /*
 110                                          * Last timestamp written in the buffer.
 111                                          */
 112
 113         struct lttng_ust_lib_ring_buffer_backend backend;       /* Associated backend */
 114
 115         DECLARE_SHMP(struct commit_counters_cold, commit_cold);
 116                                         /* Commit count per sub-buffer */
 117         long active_readers;            /*
 118                                          * Active readers count
 119                                          * standard atomic access (shared)
 120                                          */
 121                                         /* Dropped records */
 122         union v_atomic records_lost_full;       /* Buffer full */
 123         union v_atomic records_lost_wrap;       /* Nested wrap-around */
 124         union v_atomic records_lost_big;        /* Events too big */
 125         union v_atomic records_count;   /* Number of records written */
 126         union v_atomic records_overrun; /* Number of overwritten records */
 127         //wait_queue_head_t read_wait;  /* reader buffer-level wait queue */
 128         int finalized;                  /* buffer has been finalized */
 129         unsigned long get_subbuf_consumed;      /* Read-side consumed */
 130         unsigned long prod_snapshot;    /* Producer count snapshot */
 131         unsigned long cons_snapshot;    /* Consumer count snapshot */
 132         unsigned int get_subbuf:1;      /* Sub-buffer being held by reader */
 133         /* shmp pointer to self */
 134         DECLARE_SHMP(struct lttng_ust_lib_ring_buffer, self);
 135         char padding[RB_RING_BUFFER_PADDING];
 136 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 137
 138 static inline
 139 void *channel_get_private(struct channel *chan)
 140 {
 141         return ((char *) chan) + chan->priv_data_offset;
 142 }
 143
 144 #ifndef __rb_same_type
 145 #define __rb_same_type(a, b)    __builtin_types_compatible_p(typeof(a), typeof(b))
 146 #endif
 147
 148 /*
 149  * Issue warnings and disable channels upon internal error.
 150  * Can receive struct lttng_ust_lib_ring_buffer or struct lttng_ust_lib_ring_buffer_backend
 151  * parameters.
 152  */
 153 #define CHAN_WARN_ON(c, cond)                                           \
 154         ({                                                              \
 155                 struct channel *__chan;                                 \
 156                 int _____ret = caa_unlikely(cond);                              \
 157                 if (_____ret) {                                         \
 158                         if (__rb_same_type(*(c), struct channel_backend))       \
 159                                 __chan = caa_container_of((void *) (c), \
 160                                                         struct channel, \
 161                                                         backend);       \
 162                         else if (__rb_same_type(*(c), struct channel))  \
 163                                 __chan = (void *) (c);                  \
 164                         else                                            \
 165                                 BUG_ON(1);                              \
 166                         uatomic_inc(&__chan->record_disabled);          \
 167                         WARN_ON(1);                                     \
 168                 }                                                       \
 169                 _____ret = _____ret; /* For clang "unused result". */   \
 170         })
 171
 172 #endif /* _LTTNG_RING_BUFFER_FRONTEND_TYPES_H */