libringbuffer/frontend_types.h

   1 #ifndef _LINUX_RING_BUFFER_FRONTEND_TYPES_H
   2 #define _LINUX_RING_BUFFER_FRONTEND_TYPES_H
   3
   4 /*
   5  * linux/ringbuffer/frontend_types.h
   6  *
   7  * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Ring Buffer Library Synchronization Header (types).
  10  *
  11  * Author:
  12  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  13  *
  14  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  15  *
  16  * Dual LGPL v2.1/GPL v2 license.
  17  */
  18
  19 #include <string.h>
  20
  21 #include <urcu/list.h>
  22 #include <urcu/uatomic.h>
  23
  24 #include "lttng/core.h"
  25
  26 #include <lttng/usterr-signal-safe.h>
  27 #include <lttng/ringbuffer-config.h>
  28 #include "backend_types.h"
  29 #include "shm_internal.h"
  30 #include "vatomic.h"
  31
  32 /*
  33  * A switch is done during tracing or as a final flush after tracing (so it
  34  * won't write in the new sub-buffer).
  35  */
  36 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
  37
  38 /* channel: collection of per-cpu ring buffers. */
  39 struct channel {
  40         int record_disabled;
  41         unsigned long commit_count_mask;        /*
  42                                                  * Commit count mask, removing
  43                                                  * the MSBs corresponding to
  44                                                  * bits used to represent the
  45                                                  * subbuffer index.
  46                                                  */
  47
  48         unsigned long switch_timer_interval;    /* Buffer flush (jiffies) */
  49         unsigned long read_timer_interval;      /* Reader wakeup (jiffies) */
  50         //wait_queue_head_t read_wait;          /* reader wait queue */
  51         int finalized;                          /* Has channel been finalized */
  52         size_t priv_data_offset;
  53         /*
  54          * Associated backend contains a variable-length array. Needs to
  55          * be last member.
  56          */
  57         struct channel_backend backend;         /* Associated backend */
  58 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  59
  60 /* Per-subbuffer commit counters used on the hot path */
  61 struct commit_counters_hot {
  62         union v_atomic cc;              /* Commit counter */
  63         union v_atomic seq;             /* Consecutive commits */
  64 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  65
  66 /* Per-subbuffer commit counters used only on cold paths */
  67 struct commit_counters_cold {
  68         union v_atomic cc_sb;           /* Incremented _once_ at sb switch */
  69 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
  70
  71 /* ring buffer state */
  72 struct lttng_ust_lib_ring_buffer {
  73         /* First 32 bytes cache-hot cacheline */
  74         union v_atomic offset;          /* Current offset in the buffer */
  75         DECLARE_SHMP(struct commit_counters_hot, commit_hot);
  76                                         /* Commit count per sub-buffer */
  77         long consumed;                  /*
  78                                          * Current offset in the buffer
  79                                          * standard atomic access (shared)
  80                                          */
  81         int record_disabled;
  82         /* End of first 32 bytes cacheline */
  83         union v_atomic last_tsc;        /*
  84                                          * Last timestamp written in the buffer.
  85                                          */
  86
  87         struct lttng_ust_lib_ring_buffer_backend backend;       /* Associated backend */
  88
  89         DECLARE_SHMP(struct commit_counters_cold, commit_cold);
  90                                         /* Commit count per sub-buffer */
  91         long active_readers;            /*
  92                                          * Active readers count
  93                                          * standard atomic access (shared)
  94                                          */
  95         long active_shadow_readers;
  96                                         /* Dropped records */
  97         union v_atomic records_lost_full;       /* Buffer full */
  98         union v_atomic records_lost_wrap;       /* Nested wrap-around */
  99         union v_atomic records_lost_big;        /* Events too big */
 100         union v_atomic records_count;   /* Number of records written */
 101         union v_atomic records_overrun; /* Number of overwritten records */
 102         //wait_queue_head_t read_wait;  /* reader buffer-level wait queue */
 103         int finalized;                  /* buffer has been finalized */
 104         //struct timer_list switch_timer;       /* timer for periodical switch */
 105         //struct timer_list read_timer; /* timer for read poll */
 106         unsigned long get_subbuf_consumed;      /* Read-side consumed */
 107         unsigned long prod_snapshot;    /* Producer count snapshot */
 108         unsigned long cons_snapshot;    /* Consumer count snapshot */
 109         int get_subbuf:1;               /* Sub-buffer being held by reader */
 110         int switch_timer_enabled:1;     /* Protected by ring_buffer_nohz_lock */
 111         int read_timer_enabled:1;       /* Protected by ring_buffer_nohz_lock */
 112         /* shmp pointer to self */
 113         DECLARE_SHMP(struct lttng_ust_lib_ring_buffer, self);
 114 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 115
 116 static inline
 117 void *channel_get_private(struct channel *chan)
 118 {
 119         return ((char *) chan) + chan->priv_data_offset;
 120 }
 121
 122 #ifndef __rb_same_type
 123 #define __rb_same_type(a, b)    __builtin_types_compatible_p(typeof(a), typeof(b))
 124 #endif
 125
 126 /*
 127  * Issue warnings and disable channels upon internal error.
 128  * Can receive struct lttng_ust_lib_ring_buffer or struct lttng_ust_lib_ring_buffer_backend
 129  * parameters.
 130  */
 131 #define CHAN_WARN_ON(c, cond)                                           \
 132         ({                                                              \
 133                 struct channel *__chan;                                 \
 134                 int _____ret = caa_unlikely(cond);                              \
 135                 if (_____ret) {                                         \
 136                         if (__rb_same_type(*(c), struct channel_backend))       \
 137                                 __chan = caa_container_of((void *) (c), \
 138                                                         struct channel, \
 139                                                         backend);       \
 140                         else if (__rb_same_type(*(c), struct channel))  \
 141                                 __chan = (void *) (c);                  \
 142                         else                                            \
 143                                 BUG_ON(1);                              \
 144                         uatomic_inc(&__chan->record_disabled);          \
 145                         WARN_ON(1);                                     \
 146                 }                                                       \
 147                 _____ret;                                               \
 148         })
 149
 150 #endif /* _LINUX_RING_BUFFER_FRONTEND_TYPES_H */