lib/ringbuffer/frontend_types.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * lib/ringbuffer/frontend_types.h
   4  *
   5  * Ring Buffer Library Synchronization Header (types).
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  10  */
  11
  12 #ifndef _LIB_RING_BUFFER_FRONTEND_TYPES_H
  13 #define _LIB_RING_BUFFER_FRONTEND_TYPES_H
  14
  15 #include <linux/kref.h>
  16 #include <wrapper/ringbuffer/config.h>
  17 #include <wrapper/ringbuffer/backend_types.h>
  18 #include <lib/prio_heap/lttng_prio_heap.h>      /* For per-CPU read-side iterator */
  19 #include <lttng-cpuhotplug.h>
  20
  21 /*
  22  * A switch is done during tracing or as a final flush after tracing (so it
  23  * won't write in the new sub-buffer).
  24  */
  25 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
  26
  27 /* channel-level read-side iterator */
  28 struct channel_iter {
  29         /* Prio heap of buffers. Lowest timestamps at the top. */
  30         struct lttng_ptr_heap heap;     /* Heap of struct lib_ring_buffer ptrs */
  31         struct list_head empty_head;    /* Empty buffers linked-list head */
  32         int read_open;                  /* Opened for reading ? */
  33         u64 last_qs;                    /* Last quiescent state timestamp */
  34         u64 last_timestamp;             /* Last timestamp (for WARN_ON) */
  35         int last_cpu;                   /* Last timestamp cpu */
  36         /*
  37          * read() file operation state.
  38          */
  39         unsigned long len_left;
  40 };
  41
  42 /* channel: collection of per-cpu ring buffers. */
  43 struct channel {
  44         atomic_t record_disabled;
  45         unsigned long commit_count_mask;        /*
  46                                                  * Commit count mask, removing
  47                                                  * the MSBs corresponding to
  48                                                  * bits used to represent the
  49                                                  * subbuffer index.
  50                                                  */
  51
  52         struct channel_backend backend;         /* Associated backend */
  53
  54         unsigned long switch_timer_interval;    /* Buffer flush (jiffies) */
  55         unsigned long read_timer_interval;      /* Reader wakeup (jiffies) */
  56 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
  57         struct lttng_cpuhp_node cpuhp_prepare;
  58         struct lttng_cpuhp_node cpuhp_online;
  59         struct lttng_cpuhp_node cpuhp_iter_online;
  60 #else
  61         struct notifier_block cpu_hp_notifier;  /* CPU hotplug notifier */
  62         struct notifier_block hp_iter_notifier; /* hotplug iterator notifier */
  63         unsigned int cpu_hp_enable:1;           /* Enable CPU hotplug notif. */
  64         unsigned int hp_iter_enable:1;          /* Enable hp iter notif. */
  65 #endif
  66         struct notifier_block tick_nohz_notifier; /* CPU nohz notifier */
  67         wait_queue_head_t read_wait;            /* reader wait queue */
  68         wait_queue_head_t hp_wait;              /* CPU hotplug wait queue */
  69         int finalized;                          /* Has channel been finalized */
  70         struct channel_iter iter;               /* Channel read-side iterator */
  71         struct kref ref;                        /* Reference count */
  72 };
  73
  74 /* Per-subbuffer commit counters used on the hot path */
  75 struct commit_counters_hot {
  76         union v_atomic cc;              /* Commit counter */
  77         union v_atomic seq;             /* Consecutive commits */
  78 };
  79
  80 /* Per-subbuffer commit counters used only on cold paths */
  81 struct commit_counters_cold {
  82         union v_atomic cc_sb;           /* Incremented _once_ at sb switch */
  83 };
  84
  85 /* Per-buffer read iterator */
  86 struct lib_ring_buffer_iter {
  87         u64 timestamp;                  /* Current record timestamp */
  88         size_t header_len;              /* Current record header length */
  89         size_t payload_len;             /* Current record payload length */
  90
  91         struct list_head empty_node;    /* Linked list of empty buffers */
  92         unsigned long consumed, read_offset, data_size;
  93         enum {
  94                 ITER_GET_SUBBUF = 0,
  95                 ITER_TEST_RECORD,
  96                 ITER_NEXT_RECORD,
  97                 ITER_PUT_SUBBUF,
  98         } state;
  99         unsigned int allocated:1;
 100         unsigned int read_open:1;       /* Opened for reading ? */
 101 };
 102
 103 /* ring buffer state */
 104 struct lib_ring_buffer {
 105         /* First 32 bytes cache-hot cacheline */
 106         union v_atomic offset;          /* Current offset in the buffer */
 107         struct commit_counters_hot *commit_hot;
 108                                         /* Commit count per sub-buffer */
 109         atomic_long_t consumed;         /*
 110                                          * Current offset in the buffer
 111                                          * standard atomic access (shared)
 112                                          */
 113         atomic_t record_disabled;
 114         /* End of first 32 bytes cacheline */
 115         union v_atomic last_tsc;        /*
 116                                          * Last timestamp written in the buffer.
 117                                          */
 118
 119         struct lib_ring_buffer_backend backend; /* Associated backend */
 120
 121         struct commit_counters_cold *commit_cold;
 122                                         /* Commit count per sub-buffer */
 123         u64 *ts_end;                    /*
 124                                          * timestamp_end per sub-buffer.
 125                                          * Time is sampled by the
 126                                          * switch_*_end() callbacks which
 127                                          * are the last space reservation
 128                                          * performed in the sub-buffer
 129                                          * before it can be fully
 130                                          * committed and delivered. This
 131                                          * time value is then read by
 132                                          * the deliver callback,
 133                                          * performed by the last commit
 134                                          * before the buffer becomes
 135                                          * readable.
 136                                          */
 137         atomic_long_t active_readers;   /*
 138                                          * Active readers count
 139                                          * standard atomic access (shared)
 140                                          */
 141                                         /* Dropped records */
 142         union v_atomic records_lost_full;       /* Buffer full */
 143         union v_atomic records_lost_wrap;       /* Nested wrap-around */
 144         union v_atomic records_lost_big;        /* Events too big */
 145         union v_atomic records_count;   /* Number of records written */
 146         union v_atomic records_overrun; /* Number of overwritten records */
 147         wait_queue_head_t read_wait;    /* reader buffer-level wait queue */
 148         wait_queue_head_t write_wait;   /* writer buffer-level wait queue (for metadata only) */
 149         int finalized;                  /* buffer has been finalized */
 150         struct timer_list switch_timer; /* timer for periodical switch */
 151         struct timer_list read_timer;   /* timer for read poll */
 152         raw_spinlock_t raw_tick_nohz_spinlock;  /* nohz entry lock/trylock */
 153         struct lib_ring_buffer_iter iter;       /* read-side iterator */
 154         unsigned long get_subbuf_consumed;      /* Read-side consumed */
 155         unsigned long prod_snapshot;    /* Producer count snapshot */
 156         unsigned long cons_snapshot;    /* Consumer count snapshot */
 157         unsigned int get_subbuf:1,      /* Sub-buffer being held by reader */
 158                 switch_timer_enabled:1, /* Protected by ring_buffer_nohz_lock */
 159                 read_timer_enabled:1,   /* Protected by ring_buffer_nohz_lock */
 160                 quiescent:1;
 161 };
 162
 163 static inline
 164 void *channel_get_private(struct channel *chan)
 165 {
 166         return chan->backend.priv;
 167 }
 168
 169 void lib_ring_buffer_lost_event_too_big(struct channel *chan);
 170
 171 /*
 172  * Issue warnings and disable channels upon internal error.
 173  * Can receive struct lib_ring_buffer or struct lib_ring_buffer_backend
 174  * parameters.
 175  */
 176 #define CHAN_WARN_ON(c, cond)                                           \
 177         ({                                                              \
 178                 struct channel *__chan;                                 \
 179                 int _____ret = unlikely(cond);                          \
 180                 if (_____ret) {                                         \
 181                         if (__same_type(*(c), struct channel_backend))  \
 182                                 __chan = container_of((void *) (c),     \
 183                                                         struct channel, \
 184                                                         backend);       \
 185                         else if (__same_type(*(c), struct channel))     \
 186                                 __chan = (void *) (c);                  \
 187                         else                                            \
 188                                 BUG_ON(1);                              \
 189                         atomic_inc(&__chan->record_disabled);           \
 190                         WARN_ON(1);                                     \
 191                 }                                                       \
 192                 _____ret;                                               \
 193         })
 194
 195 #endif /* _LIB_RING_BUFFER_FRONTEND_TYPES_H */