include/lttng/ringbuffer-abi.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Wait-free ring buffer ABI.
   7  */
   8
   9 #ifndef _LTTNG_RING_BUFFER_ABI_H
  10 #define _LTTNG_RING_BUFFER_ABI_H
  11
  12 #define _UST_CMD(minor)                         (minor)
  13 #define _UST_CMDR(minor, type)                  (minor)
  14 #define _UST_CMDW(minor, type)                  (minor)
  15
  16 /*
  17  * Use RING_BUFFER_GET_NEXT_SUBBUF / RING_BUFFER_PUT_NEXT_SUBBUF to read and
  18  * consume sub-buffers sequentially.
  19  *
  20  * Reading sub-buffers without consuming them can be performed with:
  21  *
  22  * RING_BUFFER_SNAPSHOT
  23  * RING_BUFFER_SNAPSHOT_GET_CONSUMED
  24  * RING_BUFFER_SNAPSHOT_GET_PRODUCED
  25  *
  26  * to get the offset range to consume, and then by passing each sub-buffer
  27  * offset to RING_BUFFER_GET_SUBBUF, read the sub-buffer, and then release it
  28  * with RING_BUFFER_PUT_SUBBUF.
  29  *
  30  * Note that the "snapshot" API can be used to read the sub-buffer in reverse
  31  * order, which is useful for flight recorder snapshots.
  32  */
  33
  34 /* Get a snapshot of the current ring buffer producer and consumer positions */
  35 #define RING_BUFFER_SNAPSHOT                    _UST_CMD(0x00)
  36 /* Get the consumer position (iteration start) */
  37 #define RING_BUFFER_SNAPSHOT_GET_CONSUMED       _UST_CMDR(0x01, unsigned long)
  38 /* Get the producer position (iteration end) */
  39 #define RING_BUFFER_SNAPSHOT_GET_PRODUCED       _UST_CMDR(0x02, unsigned long)
  40 /* Get exclusive read access to the specified sub-buffer position */
  41 #define RING_BUFFER_GET_SUBBUF                  _UST_CMDW(0x03, unsigned long)
  42 /* Release exclusive sub-buffer access */
  43 #define RING_BUFFER_PUT_SUBBUF                  _UST_CMD(0x04)
  44
  45 /* Get exclusive read access to the next sub-buffer that can be read. */
  46 #define RING_BUFFER_GET_NEXT_SUBBUF             _UST_CMD(0x05)
  47 /* Release exclusive sub-buffer access, move consumer forward. */
  48 #define RING_BUFFER_PUT_NEXT_SUBBUF             _UST_CMD(0x06)
  49 /* returns the size of the current sub-buffer, without padding (for mmap). */
  50 #define RING_BUFFER_GET_SUBBUF_SIZE             _UST_CMDR(0x07, unsigned long)
  51 /* returns the size of the current sub-buffer, with padding (for splice). */
  52 #define RING_BUFFER_GET_PADDED_SUBBUF_SIZE      _UST_CMDR(0x08, unsigned long)
  53 /* returns the maximum size for sub-buffers. */
  54 #define RING_BUFFER_GET_MAX_SUBBUF_SIZE         _UST_CMDR(0x09, unsigned long)
  55 /* returns the length to mmap. */
  56 #define RING_BUFFER_GET_MMAP_LEN                _UST_CMDR(0x0A, unsigned long)
  57 /* returns the offset of the subbuffer belonging to the mmap reader. */
  58 #define RING_BUFFER_GET_MMAP_READ_OFFSET        _UST_CMDR(0x0B, unsigned long)
  59 /* flush the current sub-buffer */
  60 #define RING_BUFFER_FLUSH                       _UST_CMD(0x0C)
  61
  62 #endif /* _LTTNG_RING_BUFFER_ABI_H */