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
  33 #include <urcu/list.h>
  34 #include <urcu/uatomic.h>
  35
  36 #include <lttng/ringbuffer-config.h>
  37 #include <usterr-signal-safe.h>
  38 #include "backend_types.h"
  39 #include "shm_internal.h"
  40 #include "vatomic.h"
  41
  42 /*
  43  * A switch is done during tracing or as a final flush after tracing (so it
  44  * won't write in the new sub-buffer).
  45  */
  46 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
  47
  48 /* channel: collection of per-cpu ring buffers. */
  49 struct channel {
  50         int record_disabled;
  51         unsigned long commit_count_mask;        /*
  52                                                  * Commit count mask, removing
  53                                                  * the MSBs corresponding to
  54                                                  * bits used to represent the
  55                                                  * subbuffer index.
  56                                                  */
  57
  58         unsigned long switch_timer_interval;    /* Buffer flush (jiffies) */
  59         unsigned long read_timer_interval;      /* Reader wakeup (jiffies) */
  60         //wait_queue_head_t read_wait;          /* reader wait queue */
  61         int finalized;                          /* Has channel been finalized */
  62         size_t priv_data_offset;
  63         /* Note: padding field is missing */
  64         /*
  65          * Associated backend contains a variable-length array. Needs to
  66          * be last member.
  67          */
  68         struct channel_backend backend;         /* Associated backend */
  69 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  70
  71 /* Per-subbuffer commit counters used on the hot path */
  72 #define RB_COMMIT_COUNT_HOT_PADDING     16
  73 struct commit_counters_hot {
  74         union v_atomic cc;              /* Commit counter */
  75         union v_atomic seq;             /* Consecutive commits */
  76         char padding[RB_COMMIT_COUNT_HOT_PADDING];
  77 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  78
  79 /* Per-subbuffer commit counters used only on cold paths */
  80 #define RB_COMMIT_COUNT_COLD_PADDING    24
  81 struct commit_counters_cold {
  82         union v_atomic cc_sb;           /* Incremented _once_ at sb switch */
  83         char padding[RB_COMMIT_COUNT_COLD_PADDING];
  84 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  85
  86 /* ring buffer state */
  87 #define RB_RING_BUFFER_PADDING          64
  88 struct lttng_ust_lib_ring_buffer {
  89         /* First 32 bytes cache-hot cacheline */
  90         union v_atomic offset;          /* Current offset in the buffer */
  91         DECLARE_SHMP(struct commit_counters_hot, commit_hot);
  92                                         /* Commit count per sub-buffer */
  93         long consumed;                  /*
  94                                          * Current offset in the buffer
  95                                          * standard atomic access (shared)
  96                                          */
  97         int record_disabled;
  98         /* End of first 32 bytes cacheline */
  99         union v_atomic last_tsc;        /*
 100                                          * Last timestamp written in the buffer.
 101                                          */
 102
 103         struct lttng_ust_lib_ring_buffer_backend backend;       /* Associated backend */
 104
 105         DECLARE_SHMP(struct commit_counters_cold, commit_cold);
 106                                         /* Commit count per sub-buffer */
 107         long active_readers;            /*
 108                                          * Active readers count
 109                                          * standard atomic access (shared)
 110                                          */
 111         long active_shadow_readers;
 112                                         /* Dropped records */
 113         union v_atomic records_lost_full;       /* Buffer full */
 114         union v_atomic records_lost_wrap;       /* Nested wrap-around */
 115         union v_atomic records_lost_big;        /* Events too big */
 116         union v_atomic records_count;   /* Number of records written */
 117         union v_atomic records_overrun; /* Number of overwritten records */
 118         //wait_queue_head_t read_wait;  /* reader buffer-level wait queue */
 119         int finalized;                  /* buffer has been finalized */
 120         //struct timer_list switch_timer;       /* timer for periodical switch */
 121         //struct timer_list read_timer; /* timer for read poll */
 122         unsigned long get_subbuf_consumed;      /* Read-side consumed */
 123         unsigned long prod_snapshot;    /* Producer count snapshot */
 124         unsigned long cons_snapshot;    /* Consumer count snapshot */
 125         unsigned int get_subbuf:1,      /* Sub-buffer being held by reader */
 126                 switch_timer_enabled:1, /* Protected by ring_buffer_nohz_lock */
 127                 read_timer_enabled:1;   /* Protected by ring_buffer_nohz_lock */
 128         /* shmp pointer to self */
 129         DECLARE_SHMP(struct lttng_ust_lib_ring_buffer, self);
 130         char padding[RB_RING_BUFFER_PADDING];
 131 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 132
 133 static inline
 134 void *channel_get_private(struct channel *chan)
 135 {
 136         return ((char *) chan) + chan->priv_data_offset;
 137 }
 138
 139 #ifndef __rb_same_type
 140 #define __rb_same_type(a, b)    __builtin_types_compatible_p(typeof(a), typeof(b))
 141 #endif
 142
 143 /*
 144  * Issue warnings and disable channels upon internal error.
 145  * Can receive struct lttng_ust_lib_ring_buffer or struct lttng_ust_lib_ring_buffer_backend
 146  * parameters.
 147  */
 148 #define CHAN_WARN_ON(c, cond)                                           \
 149         ({                                                              \
 150                 struct channel *__chan;                                 \
 151                 int _____ret = caa_unlikely(cond);                              \
 152                 if (_____ret) {                                         \
 153                         if (__rb_same_type(*(c), struct channel_backend))       \
 154                                 __chan = caa_container_of((void *) (c), \
 155                                                         struct channel, \
 156                                                         backend);       \
 157                         else if (__rb_same_type(*(c), struct channel))  \
 158                                 __chan = (void *) (c);                  \
 159                         else                                            \
 160                                 BUG_ON(1);                              \
 161                         uatomic_inc(&__chan->record_disabled);          \
 162                         WARN_ON(1);                                     \
 163                 }                                                       \
 164                 _____ret;                                               \
 165         })
 166
 167 #endif /* _LTTNG_RING_BUFFER_FRONTEND_TYPES_H */