lib/ringbuffer/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 "../../wrapper/ringbuffer/config.h"
  20 #include "../../wrapper/ringbuffer/backend_types.h"
  21 #include "../../wrapper/prio_heap.h"    /* For per-CPU read-side iterator */
  22
  23 /*
  24  * A switch is done during tracing or as a final flush after tracing (so it
  25  * won't write in the new sub-buffer).
  26  */
  27 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
  28
  29 /* channel-level read-side iterator */
  30 struct channel_iter {
  31         /* Prio heap of buffers. Lowest timestamps at the top. */
  32         struct ptr_heap heap;           /* Heap of struct lib_ring_buffer ptrs */
  33         struct list_head empty_head;    /* Empty buffers linked-list head */
  34         int read_open;                  /* Opened for reading ? */
  35         u64 last_qs;                    /* Last quiescent state timestamp */
  36         u64 last_timestamp;             /* Last timestamp (for WARN_ON) */
  37         int last_cpu;                   /* Last timestamp cpu */
  38         /*
  39          * read() file operation state.
  40          */
  41         unsigned long len_left;
  42 };
  43
  44 /* channel: collection of per-cpu ring buffers. */
  45 struct channel {
  46         atomic_t record_disabled;
  47         unsigned long commit_count_mask;        /*
  48                                                  * Commit count mask, removing
  49                                                  * the MSBs corresponding to
  50                                                  * bits used to represent the
  51                                                  * subbuffer index.
  52                                                  */
  53
  54         struct channel_backend backend;         /* Associated backend */
  55
  56         unsigned long switch_timer_interval;    /* Buffer flush (jiffies) */
  57         unsigned long read_timer_interval;      /* Reader wakeup (jiffies) */
  58         struct notifier_block cpu_hp_notifier;  /* CPU hotplug notifier */
  59         struct notifier_block tick_nohz_notifier; /* CPU nohz notifier */
  60         struct notifier_block hp_iter_notifier; /* hotplug iterator notifier */
  61         int cpu_hp_enable:1;                    /* Enable CPU hotplug notif. */
  62         int hp_iter_enable:1;                   /* Enable hp iter notif. */
  63         wait_queue_head_t read_wait;            /* reader wait queue */
  64         struct channel_iter iter;               /* Channel read-side iterator */
  65         atomic_long_t read_ref;                 /* Reader reference count */
  66 };
  67
  68 /* Per-subbuffer commit counters used on the hot path */
  69 struct commit_counters_hot {
  70         union v_atomic cc;              /* Commit counter */
  71         union v_atomic seq;             /* Consecutive commits */
  72 };
  73
  74 /* Per-subbuffer commit counters used only on cold paths */
  75 struct commit_counters_cold {
  76         union v_atomic cc_sb;           /* Incremented _once_ at sb switch */
  77 };
  78
  79 /* Per-buffer read iterator */
  80 struct lib_ring_buffer_iter {
  81         u64 timestamp;                  /* Current record timestamp */
  82         size_t header_len;              /* Current record header length */
  83         size_t payload_len;             /* Current record payload length */
  84
  85         struct list_head empty_node;    /* Linked list of empty buffers */
  86         unsigned long consumed, read_offset, data_size;
  87         enum {
  88                 ITER_GET_SUBBUF = 0,
  89                 ITER_TEST_RECORD,
  90                 ITER_NEXT_RECORD,
  91                 ITER_PUT_SUBBUF,
  92         } state;
  93         int allocated:1;
  94         int read_open:1;                /* Opened for reading ? */
  95 };
  96
  97 /* ring buffer state */
  98 struct lib_ring_buffer {
  99         /* First 32 bytes cache-hot cacheline */
 100         union v_atomic offset;          /* Current offset in the buffer */
 101         struct commit_counters_hot *commit_hot;
 102                                         /* Commit count per sub-buffer */
 103         atomic_long_t consumed;         /*
 104                                          * Current offset in the buffer
 105                                          * standard atomic access (shared)
 106                                          */
 107         atomic_t 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 lib_ring_buffer_backend backend; /* Associated backend */
 114
 115         struct commit_counters_cold *commit_cold;
 116                                         /* Commit count per sub-buffer */
 117         atomic_long_t 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         struct timer_list switch_timer; /* timer for periodical switch */
 130         struct timer_list read_timer;   /* timer for read poll */
 131         raw_spinlock_t raw_tick_nohz_spinlock;  /* nohz entry lock/trylock */
 132         struct lib_ring_buffer_iter iter;       /* read-side iterator */
 133         unsigned long get_subbuf_consumed;      /* Read-side consumed */
 134         unsigned long prod_snapshot;    /* Producer count snapshot */
 135         unsigned long cons_snapshot;    /* Consumer count snapshot */
 136         int get_subbuf:1;               /* Sub-buffer being held by reader */
 137         int switch_timer_enabled:1;     /* Protected by ring_buffer_nohz_lock */
 138         int read_timer_enabled:1;       /* Protected by ring_buffer_nohz_lock */
 139 };
 140
 141 /*
 142  * Issue warnings and disable channels upon internal error.
 143  * Can receive struct lib_ring_buffer or struct lib_ring_buffer_backend
 144  * parameters.
 145  */
 146 #define CHAN_WARN_ON(c, cond)                                           \
 147         ({                                                              \
 148                 struct channel *__chan;                                 \
 149                 int _____ret = unlikely(cond);                          \
 150                 if (_____ret) {                                         \
 151                         if (__same_type(*(c), struct channel_backend))  \
 152                                 __chan = container_of((void *) (c),     \
 153                                                         struct channel, \
 154                                                         backend);       \
 155                         else if (__same_type(*(c), struct channel))     \
 156                                 __chan = (void *) (c);                  \
 157                         else                                            \
 158                                 BUG_ON(1);                              \
 159                         atomic_inc(&__chan->record_disabled);           \
 160                         WARN_ON(1);                                     \
 161                 }                                                       \
 162                 _____ret;                                               \
 163         })
 164
 165 #endif /* _LINUX_RING_BUFFER_FRONTEND_TYPES_H */