[lttng-ust.git] / libringbuffer / backend.h

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Ring buffer backend (API).
 *
 * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
 * the reader in flight recorder mode.
 */

#ifndef _LTTNG_RING_BUFFER_BACKEND_H
#define _LTTNG_RING_BUFFER_BACKEND_H

#include <stddef.h>
#include <unistd.h>

/* Internal helpers */
#include "backend_internal.h"
#include "frontend_internal.h"

/* Ring buffer backend API */

/* Ring buffer backend access (read/write) */

__attribute__((visibility("hidden")))
extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb,
				   size_t offset, void *dest, size_t len,
				   struct lttng_ust_shm_handle *handle);

__attribute__((visibility("hidden")))
extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb,
				     size_t offset, void *dest, size_t len,
				     struct lttng_ust_shm_handle *handle);

/*
 * Return the address where a given offset is located.
 * Should be used to get the current subbuffer header pointer. Given we know
 * it's never on a page boundary, it's safe to write directly to this address,
 * as long as the write is never bigger than a page size.
 */
__attribute__((visibility("hidden")))
extern void *
lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
			       size_t offset,
			       struct lttng_ust_shm_handle *handle);

__attribute__((visibility("hidden")))
extern void *
lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
				    size_t offset,
				    struct lttng_ust_shm_handle *handle);

/**
 * lib_ring_buffer_write - write data to a buffer backend
 * @config : ring buffer instance configuration
 * @ctx: ring buffer context. (input arguments only)
 * @src : source pointer to copy from
 * @len : length of data to copy
 *
 * This function copies "len" bytes of data from a source pointer to a buffer
 * backend, at the current context offset. This is more or less a buffer
 * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
 * if copy is crossing a page boundary.
 */
static inline __attribute__((always_inline))
void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,
			   struct lttng_ust_lib_ring_buffer_ctx *ctx,
			   const void *src, size_t len)
{
	struct channel_backend *chanb = &ctx->chan->backend;
	struct lttng_ust_shm_handle *handle = ctx->chan->handle;
	size_t offset = ctx->buf_offset;
	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
	void *p;

	if (caa_unlikely(!len))
		return;
	/*
	 * Underlying layer should never ask for writes across
	 * subbuffers.
	 */
	CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
	backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
	if (caa_unlikely(!backend_pages)) {
		if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
			return;
	}
	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	if (caa_unlikely(!p))
		return;
	lib_ring_buffer_do_copy(config, p, src, len);
	ctx->buf_offset += len;
}

/*
 * Copy up to @len string bytes from @src to @dest. Stop whenever a NULL
 * terminating character is found in @src. Returns the number of bytes
 * copied. Does *not* terminate @dest with NULL terminating character.
 */
static inline __attribute__((always_inline))
size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
		char *dest, const char *src, size_t len)
{
	size_t count;

	for (count = 0; count < len; count++) {
		char c;

		/*
		 * Only read source character once, in case it is
		 * modified concurrently.
		 */
		c = CMM_LOAD_SHARED(src[count]);
		if (!c)
			break;
		lib_ring_buffer_do_copy(config, &dest[count], &c, 1);
	}
	return count;
}

/**
 * lib_ring_buffer_strcpy - write string data to a buffer backend
 * @config : ring buffer instance configuration
 * @ctx: ring buffer context. (input arguments only)
 * @src : source pointer to copy from
 * @len : length of data to copy
 * @pad : character to use for padding
 *
 * This function copies @len - 1 bytes of string data from a source
 * pointer to a buffer backend, followed by a terminating '\0'
 * character, at the current context offset. This is more or less a
 * buffer backend-specific strncpy() operation. If a terminating '\0'
 * character is found in @src before @len - 1 characters are copied, pad
 * the buffer with @pad characters (e.g. '#').
 */
static inline __attribute__((always_inline))
void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
			   struct lttng_ust_lib_ring_buffer_ctx *ctx,
			   const char *src, size_t len, char pad)
{
	struct channel_backend *chanb = &ctx->chan->backend;
	struct lttng_ust_shm_handle *handle = ctx->chan->handle;
	size_t count;
	size_t offset = ctx->buf_offset;
	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
	void *p;

	if (caa_unlikely(!len))
		return;
	/*
	 * Underlying layer should never ask for writes across
	 * subbuffers.
	 */
	CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
	backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
	if (caa_unlikely(!backend_pages)) {
		if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
			return;
	}
	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	if (caa_unlikely(!p))
		return;

	count = lib_ring_buffer_do_strcpy(config, p, src, len - 1);
	offset += count;
	/* Padding */
	if (caa_unlikely(count < len - 1)) {
		size_t pad_len = len - 1 - count;

		p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
		if (caa_unlikely(!p))
			return;
		lib_ring_buffer_do_memset(p, pad, pad_len);
		offset += pad_len;
	}
	/* Final '\0' */
	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	if (caa_unlikely(!p))
		return;
	lib_ring_buffer_do_memset(p, '\0', 1);
	ctx->buf_offset += len;
}

/**
 * lib_ring_buffer_pstrcpy - write to a buffer backend P-string
 * @config : ring buffer instance configuration
 * @ctx: ring buffer context. (input arguments only)
 * @src : source pointer to copy from
 * @len : length of data to copy
 * @pad : character to use for padding
 *
 * This function copies up to @len bytes of data from a source pointer
 * to a Pascal String into the buffer backend. If a terminating '\0'
 * character is found in @src before @len characters are copied, pad the
 * buffer with @pad characters (e.g.  '\0').
 *
 * The length of the pascal strings in the ring buffer is explicit: it
 * is either the array or sequence length.
 */
static inline __attribute__((always_inline))
void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config,
			   struct lttng_ust_lib_ring_buffer_ctx *ctx,
			   const char *src, size_t len, char pad)
{
	struct channel_backend *chanb = &ctx->chan->backend;
	struct lttng_ust_shm_handle *handle = ctx->chan->handle;
	size_t count;
	size_t offset = ctx->buf_offset;
	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
	void *p;

	if (caa_unlikely(!len))
		return;
	/*
	 * Underlying layer should never ask for writes across
	 * subbuffers.
	 */
	CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
	backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
	if (caa_unlikely(!backend_pages)) {
		if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
			return;
	}
	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	if (caa_unlikely(!p))
		return;

	count = lib_ring_buffer_do_strcpy(config, p, src, len);
	offset += count;
	/* Padding */
	if (caa_unlikely(count < len)) {
		size_t pad_len = len - count;

		p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
		if (caa_unlikely(!p))
			return;
		lib_ring_buffer_do_memset(p, pad, pad_len);
	}
	ctx->buf_offset += len;
}

/*
 * This accessor counts the number of unread records in a buffer.
 * It only provides a consistent value if no reads not writes are performed
 * concurrently.
 */
static inline
unsigned long lib_ring_buffer_get_records_unread(
				const struct lttng_ust_lib_ring_buffer_config *config,
				struct lttng_ust_lib_ring_buffer *buf,
				struct lttng_ust_shm_handle *handle)
{
	struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
	unsigned long records_unread = 0, sb_bindex;
	unsigned int i;
	struct lttng_ust_lib_ring_buffer_channel *chan;

	chan = shmp(handle, bufb->chan);
	if (!chan)
		return 0;
	for (i = 0; i < chan->backend.num_subbuf; i++) {
		struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb;
		struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
		struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;

		wsb = shmp_index(handle, bufb->buf_wsb, i);
		if (!wsb)
			return 0;
		sb_bindex = subbuffer_id_get_index(config, wsb->id);
		rpages = shmp_index(handle, bufb->array, sb_bindex);
		if (!rpages)
			return 0;
		backend_pages = shmp(handle, rpages->shmp);
		if (!backend_pages)
			return 0;
		records_unread += v_read(config, &backend_pages->records_unread);
	}
	if (config->mode == RING_BUFFER_OVERWRITE) {
		struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
		struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;

		sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
		rpages = shmp_index(handle, bufb->array, sb_bindex);
		if (!rpages)
			return 0;
		backend_pages = shmp(handle, rpages->shmp);
		if (!backend_pages)
			return 0;
		records_unread += v_read(config, &backend_pages->records_unread);
	}
	return records_unread;
}

#endif /* _LTTNG_RING_BUFFER_BACKEND_H */
Commit	Line	Data
852c2936	1	/*
c0c0989a	2	* SPDX-License-Identifier: LGPL-2.1-only
852c2936	3	*
e92f3e28 MD	4	* Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
e92f3e28 MD	5	*
c0c0989a	6	* Ring buffer backend (API).
852c2936 MD	7	*
	8	* Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
	9	* the reader in flight recorder mode.
	10	*/
	11
c0c0989a MJ	12	#ifndef _LTTNG_RING_BUFFER_BACKEND_H
	13	#define _LTTNG_RING_BUFFER_BACKEND_H
	14
b4051ad8	15	#include <stddef.h>
14641deb MD	16	#include <unistd.h>
14641deb MD	17
852c2936	18	/* Internal helpers */
4931a13e MD	19	#include "backend_internal.h"
4931a13e MD	20	#include "frontend_internal.h"
852c2936 MD	21
	22	/* Ring buffer backend API */
	23
	24	/* Ring buffer backend access (read/write) */
	25
ddabe860	26	__attribute__((visibility("hidden")))
4cfec15c	27	extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	28	size_t offset, void *dest, size_t len,
38fae1d3	29	struct lttng_ust_shm_handle *handle);
852c2936	30
ddabe860	31	__attribute__((visibility("hidden")))
4cfec15c	32	extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	33	size_t offset, void *dest, size_t len,
38fae1d3	34	struct lttng_ust_shm_handle *handle);
852c2936	35
852c2936 MD	36	/*
	37	* Return the address where a given offset is located.
	38	* Should be used to get the current subbuffer header pointer. Given we know
	39	* it's never on a page boundary, it's safe to write directly to this address,
	40	* as long as the write is never bigger than a page size.
	41	*/
ddabe860	42	__attribute__((visibility("hidden")))
852c2936	43	extern void *
4cfec15c	44	lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	45	size_t offset,
38fae1d3	46	struct lttng_ust_shm_handle *handle);
ddabe860 MJ	47
ddabe860 MJ	48	__attribute__((visibility("hidden")))
852c2936	49	extern void *
4cfec15c	50	lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	51	size_t offset,
38fae1d3	52	struct lttng_ust_shm_handle *handle);
852c2936 MD	53
	54	/**
	55	* lib_ring_buffer_write - write data to a buffer backend
	56	* @config : ring buffer instance configuration
	57	* @ctx: ring buffer context. (input arguments only)
	58	* @src : source pointer to copy from
	59	* @len : length of data to copy
	60	*
	61	* This function copies "len" bytes of data from a source pointer to a buffer
	62	* backend, at the current context offset. This is more or less a buffer
	63	* backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
	64	* if copy is crossing a page boundary.
	65	*/
00d0f8eb	66	static inline __attribute__((always_inline))
4cfec15c MD	67	void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	68	struct lttng_ust_lib_ring_buffer_ctx *ctx,
852c2936 MD	69	const void *src, size_t len)
852c2936 MD	70	{
852c2936	71	struct channel_backend *chanb = &ctx->chan->backend;
aab8b172	72	struct lttng_ust_shm_handle *handle = ctx->chan->handle;
852c2936	73	size_t offset = ctx->buf_offset;
15500a1b MD	74	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
15500a1b MD	75	void *p;
852c2936	76
0bf3c920 MD	77	if (caa_unlikely(!len))
0bf3c920 MD	78	return;
a6352fd4 MD	79	/*
	80	* Underlying layer should never ask for writes across
	81	* subbuffers.
	82	*/
a3492932 MD	83	CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
	84	backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
	85	if (caa_unlikely(!backend_pages)) {
	86	if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
	87	return;
	88	}
15500a1b MD	89	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	90	if (caa_unlikely(!p))
	91	return;
	92	lib_ring_buffer_do_copy(config, p, src, len);
852c2936 MD	93	ctx->buf_offset += len;
	94	}
	95
a44c74d9 MD	96	/*
	97	* Copy up to @len string bytes from @src to @dest. Stop whenever a NULL
	98	* terminating character is found in @src. Returns the number of bytes
	99	* copied. Does not terminate @dest with NULL terminating character.
	100	*/
00d0f8eb	101	static inline __attribute__((always_inline))
a44c74d9 MD	102	size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
	103	char dest, const char src, size_t len)
	104	{
	105	size_t count;
	106
	107	for (count = 0; count < len; count++) {
	108	char c;
	109
	110	/*
	111	* Only read source character once, in case it is
	112	* modified concurrently.
	113	*/
	114	c = CMM_LOAD_SHARED(src[count]);
	115	if (!c)
	116	break;
	117	lib_ring_buffer_do_copy(config, &dest[count], &c, 1);
	118	}
	119	return count;
	120	}
	121
	122	/**
	123	* lib_ring_buffer_strcpy - write string data to a buffer backend
	124	* @config : ring buffer instance configuration
	125	* @ctx: ring buffer context. (input arguments only)
	126	* @src : source pointer to copy from
	127	* @len : length of data to copy
	128	* @pad : character to use for padding
	129	*
	130	* This function copies @len - 1 bytes of string data from a source
	131	* pointer to a buffer backend, followed by a terminating '\0'
	132	* character, at the current context offset. This is more or less a
	133	* buffer backend-specific strncpy() operation. If a terminating '\0'
	134	* character is found in @src before @len - 1 characters are copied, pad
	135	* the buffer with @pad characters (e.g. '#').
	136	*/
00d0f8eb	137	static inline __attribute__((always_inline))
a44c74d9 MD	138	void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
a44c74d9 MD	139	struct lttng_ust_lib_ring_buffer_ctx *ctx,
b4c8bf2f	140	const char *src, size_t len, char pad)
a44c74d9	141	{
a44c74d9	142	struct channel_backend *chanb = &ctx->chan->backend;
aab8b172	143	struct lttng_ust_shm_handle *handle = ctx->chan->handle;
a3492932	144	size_t count;
a44c74d9	145	size_t offset = ctx->buf_offset;
a3492932 MD	146	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
a3492932 MD	147	void *p;
a44c74d9 MD	148
	149	if (caa_unlikely(!len))
	150	return;
a44c74d9 MD	151	/*
	152	* Underlying layer should never ask for writes across
	153	* subbuffers.
	154	*/
a3492932 MD	155	CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
	156	backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
	157	if (caa_unlikely(!backend_pages)) {
	158	if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
	159	return;
	160	}
	161	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	162	if (caa_unlikely(!p))
	163	return;
	164
	165	count = lib_ring_buffer_do_strcpy(config, p, src, len - 1);
a44c74d9 MD	166	offset += count;
	167	/* Padding */
	168	if (caa_unlikely(count < len - 1)) {
	169	size_t pad_len = len - 1 - count;
	170
a3492932 MD	171	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	172	if (caa_unlikely(!p))
	173	return;
	174	lib_ring_buffer_do_memset(p, pad, pad_len);
a44c74d9 MD	175	offset += pad_len;
	176	}
	177	/* Final '\0' */
a3492932 MD	178	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	179	if (caa_unlikely(!p))
	180	return;
	181	lib_ring_buffer_do_memset(p, '\0', 1);
a44c74d9 MD	182	ctx->buf_offset += len;
	183	}
	184
879f9b0a MD	185	/**
	186	* lib_ring_buffer_pstrcpy - write to a buffer backend P-string
	187	* @config : ring buffer instance configuration
	188	* @ctx: ring buffer context. (input arguments only)
	189	* @src : source pointer to copy from
	190	* @len : length of data to copy
	191	* @pad : character to use for padding
	192	*
	193	* This function copies up to @len bytes of data from a source pointer
	194	* to a Pascal String into the buffer backend. If a terminating '\0'
	195	* character is found in @src before @len characters are copied, pad the
	196	* buffer with @pad characters (e.g. '\0').
	197	*
	198	* The length of the pascal strings in the ring buffer is explicit: it
	199	* is either the array or sequence length.
	200	*/
	201	static inline __attribute__((always_inline))
	202	void lib_ring_buffer_pstrcpy(const struct lttng_ust_lib_ring_buffer_config *config,
	203	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	204	const char *src, size_t len, char pad)
	205	{
	206	struct channel_backend *chanb = &ctx->chan->backend;
aab8b172	207	struct lttng_ust_shm_handle *handle = ctx->chan->handle;
879f9b0a MD	208	size_t count;
	209	size_t offset = ctx->buf_offset;
	210	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
	211	void *p;
	212
	213	if (caa_unlikely(!len))
	214	return;
	215	/*
	216	* Underlying layer should never ask for writes across
	217	* subbuffers.
	218	*/
	219	CHAN_WARN_ON(chanb, (offset & (chanb->buf_size - 1)) + len > chanb->buf_size);
	220	backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
	221	if (caa_unlikely(!backend_pages)) {
	222	if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
	223	return;
	224	}
	225	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	226	if (caa_unlikely(!p))
	227	return;
	228
	229	count = lib_ring_buffer_do_strcpy(config, p, src, len);
	230	offset += count;
	231	/* Padding */
	232	if (caa_unlikely(count < len)) {
	233	size_t pad_len = len - count;
	234
	235	p = shmp_index(handle, backend_pages->p, offset & (chanb->subbuf_size - 1));
	236	if (caa_unlikely(!p))
	237	return;
	238	lib_ring_buffer_do_memset(p, pad, pad_len);
	239	}
	240	ctx->buf_offset += len;
	241	}
	242
852c2936 MD	243	/*
	244	* This accessor counts the number of unread records in a buffer.
	245	* It only provides a consistent value if no reads not writes are performed
	246	* concurrently.
	247	*/
	248	static inline
	249	unsigned long lib_ring_buffer_get_records_unread(
4cfec15c MD	250	const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	251	struct lttng_ust_lib_ring_buffer *buf,
38fae1d3	252	struct lttng_ust_shm_handle *handle)
852c2936	253	{
4cfec15c	254	struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
15500a1b	255	unsigned long records_unread = 0, sb_bindex;
852c2936	256	unsigned int i;
5198080d	257	struct lttng_ust_lib_ring_buffer_channel *chan;
852c2936	258
15500a1b MD	259	chan = shmp(handle, bufb->chan);
	260	if (!chan)
	261	return 0;
	262	for (i = 0; i < chan->backend.num_subbuf; i++) {
	263	struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb;
	264	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
	265	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
	266
	267	wsb = shmp_index(handle, bufb->buf_wsb, i);
	268	if (!wsb)
	269	return 0;
	270	sb_bindex = subbuffer_id_get_index(config, wsb->id);
	271	rpages = shmp_index(handle, bufb->array, sb_bindex);
	272	if (!rpages)
	273	return 0;
	274	backend_pages = shmp(handle, rpages->shmp);
	275	if (!backend_pages)
	276	return 0;
	277	records_unread += v_read(config, &backend_pages->records_unread);
852c2936 MD	278	}
852c2936 MD	279	if (config->mode == RING_BUFFER_OVERWRITE) {
15500a1b MD	280	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
	281	struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
	282
	283	sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
	284	rpages = shmp_index(handle, bufb->array, sb_bindex);
	285	if (!rpages)
	286	return 0;
	287	backend_pages = shmp(handle, rpages->shmp);
	288	if (!backend_pages)
	289	return 0;
	290	records_unread += v_read(config, &backend_pages->records_unread);
852c2936 MD	291	}
	292	return records_unread;
	293	}
	294
e92f3e28	295	#endif /* _LTTNG_RING_BUFFER_BACKEND_H */