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

#ifndef _LTTNG_RING_BUFFER_BACKEND_H
#define _LTTNG_RING_BUFFER_BACKEND_H

/*
 * libringbuffer/backend.h
 *
 * Ring buffer backend (API).
 *
 * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
 * the reader in flight recorder mode.
 */

#include <unistd.h>

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

/* Ring buffer backend API */

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

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);

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.
 */
extern void *
lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
			       size_t offset,
			       struct lttng_ust_shm_handle *handle);
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
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 lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
	struct channel_backend *chanb = &ctx->chan->backend;
	struct lttng_ust_shm_handle *handle = ctx->handle;
	size_t sbidx;
	size_t offset = ctx->buf_offset;
	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
	unsigned long sb_bindex, id;

	if (caa_unlikely(!len))
		return;
	offset &= chanb->buf_size - 1;
	sbidx = offset >> chanb->subbuf_size_order;
	id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
	sb_bindex = subbuffer_id_get_index(config, id);
	rpages = shmp_index(handle, bufb->array, sb_bindex);
	CHAN_WARN_ON(ctx->chan,
		     config->mode == RING_BUFFER_OVERWRITE
		     && subbuffer_id_is_noref(config, id));
	/*
	 * Underlying layer should never ask for writes across
	 * subbuffers.
	 */
	CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
	lib_ring_buffer_do_copy(config,
				shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)),
				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
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
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, int pad)
{
	struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
	struct channel_backend *chanb = &ctx->chan->backend;
	struct lttng_ust_shm_handle *handle = ctx->handle;
	size_t sbidx, count;
	size_t offset = ctx->buf_offset;
	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
	unsigned long sb_bindex, id;

	if (caa_unlikely(!len))
		return;
	offset &= chanb->buf_size - 1;
	sbidx = offset >> chanb->subbuf_size_order;
	id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
	sb_bindex = subbuffer_id_get_index(config, id);
	rpages = shmp_index(handle, bufb->array, sb_bindex);
	CHAN_WARN_ON(ctx->chan,
		     config->mode == RING_BUFFER_OVERWRITE
		     && subbuffer_id_is_noref(config, id));
	/*
	 * Underlying layer should never ask for writes across
	 * subbuffers.
	 */
	CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
	count = lib_ring_buffer_do_strcpy(config,
			shmp_index(handle, shmp(handle, rpages->shmp)->p,
				offset & (chanb->subbuf_size - 1)),
			src, len - 1);
	offset += count;
	/* Padding */
	if (caa_unlikely(count < len - 1)) {
		size_t pad_len = len - 1 - count;

		lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,
				offset & (chanb->subbuf_size - 1)),
			pad, pad_len);
		offset += pad_len;
	}
	/* Final '\0' */
	lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,
				offset & (chanb->subbuf_size - 1)),
			'\0', 1);
	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;
	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages;
	unsigned long records_unread = 0, sb_bindex, id;
	unsigned int i;

	for (i = 0; i < shmp(handle, bufb->chan)->backend.num_subbuf; i++) {
		id = shmp_index(handle, bufb->buf_wsb, i)->id;
		sb_bindex = subbuffer_id_get_index(config, id);
		pages = shmp_index(handle, bufb->array, sb_bindex);
		records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread);
	}
	if (config->mode == RING_BUFFER_OVERWRITE) {
		id = bufb->buf_rsb.id;
		sb_bindex = subbuffer_id_get_index(config, id);
		pages = shmp_index(handle, bufb->array, sb_bindex);
		records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread);
	}
	return records_unread;
}

#endif /* _LTTNG_RING_BUFFER_BACKEND_H */
Commit	Line	Data
e92f3e28 MD	1	#ifndef _LTTNG_RING_BUFFER_BACKEND_H
e92f3e28 MD	2	#define _LTTNG_RING_BUFFER_BACKEND_H
852c2936 MD	3
852c2936 MD	4	/*
e92f3e28	5	* libringbuffer/backend.h
852c2936 MD	6	*
	7	* Ring buffer backend (API).
	8	*
e92f3e28 MD	9	* Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	10	*
	11	* This library is free software; you can redistribute it and/or
	12	* modify it under the terms of the GNU Lesser General Public
	13	* License as published by the Free Software Foundation; only
	14	* version 2.1 of the License.
	15	*
	16	* This library is distributed in the hope that it will be useful,
	17	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	19	* Lesser General Public License for more details.
	20	*
	21	* You should have received a copy of the GNU Lesser General Public
	22	* License along with this library; if not, write to the Free Software
	23	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
852c2936 MD	24	*
	25	* Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
	26	* the reader in flight recorder mode.
	27	*/
	28
14641deb MD	29	#include <unistd.h>
14641deb MD	30
852c2936	31	/* Internal helpers */
4931a13e MD	32	#include "backend_internal.h"
4931a13e MD	33	#include "frontend_internal.h"
852c2936 MD	34
	35	/* Ring buffer backend API */
	36
	37	/* Ring buffer backend access (read/write) */
	38
4cfec15c	39	extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	40	size_t offset, void *dest, size_t len,
38fae1d3	41	struct lttng_ust_shm_handle *handle);
852c2936	42
4cfec15c	43	extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	44	size_t offset, void *dest, size_t len,
38fae1d3	45	struct lttng_ust_shm_handle *handle);
852c2936	46
852c2936 MD	47	/*
	48	* Return the address where a given offset is located.
	49	* Should be used to get the current subbuffer header pointer. Given we know
	50	* it's never on a page boundary, it's safe to write directly to this address,
	51	* as long as the write is never bigger than a page size.
	52	*/
	53	extern void *
4cfec15c	54	lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	55	size_t offset,
38fae1d3	56	struct lttng_ust_shm_handle *handle);
852c2936	57	extern void *
4cfec15c	58	lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
1d498196	59	size_t offset,
38fae1d3	60	struct lttng_ust_shm_handle *handle);
852c2936 MD	61
	62	/**
	63	* lib_ring_buffer_write - write data to a buffer backend
	64	* @config : ring buffer instance configuration
	65	* @ctx: ring buffer context. (input arguments only)
	66	* @src : source pointer to copy from
	67	* @len : length of data to copy
	68	*
	69	* This function copies "len" bytes of data from a source pointer to a buffer
	70	* backend, at the current context offset. This is more or less a buffer
	71	* backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
	72	* if copy is crossing a page boundary.
	73	*/
	74	static inline
4cfec15c MD	75	void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	76	struct lttng_ust_lib_ring_buffer_ctx *ctx,
852c2936 MD	77	const void *src, size_t len)
852c2936 MD	78	{
4cfec15c	79	struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
852c2936	80	struct channel_backend *chanb = &ctx->chan->backend;
38fae1d3	81	struct lttng_ust_shm_handle *handle = ctx->handle;
a6352fd4	82	size_t sbidx;
852c2936	83	size_t offset = ctx->buf_offset;
4cfec15c	84	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
852c2936 MD	85	unsigned long sb_bindex, id;
852c2936 MD	86
0bf3c920 MD	87	if (caa_unlikely(!len))
0bf3c920 MD	88	return;
852c2936 MD	89	offset &= chanb->buf_size - 1;
852c2936 MD	90	sbidx = offset >> chanb->subbuf_size_order;
4746ae29	91	id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
852c2936	92	sb_bindex = subbuffer_id_get_index(config, id);
4746ae29	93	rpages = shmp_index(handle, bufb->array, sb_bindex);
852c2936 MD	94	CHAN_WARN_ON(ctx->chan,
	95	config->mode == RING_BUFFER_OVERWRITE
	96	&& subbuffer_id_is_noref(config, id));
a6352fd4 MD	97	/*
	98	* Underlying layer should never ask for writes across
	99	* subbuffers.
	100	*/
	101	CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
	102	lib_ring_buffer_do_copy(config,
aead2025	103	shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)),
a6352fd4	104	src, len);
852c2936 MD	105	ctx->buf_offset += len;
	106	}
	107
a44c74d9 MD	108	/*
	109	* Copy up to @len string bytes from @src to @dest. Stop whenever a NULL
	110	* terminating character is found in @src. Returns the number of bytes
	111	* copied. Does not terminate @dest with NULL terminating character.
	112	*/
	113	static inline
	114	size_t lib_ring_buffer_do_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
	115	char dest, const char src, size_t len)
	116	{
	117	size_t count;
	118
	119	for (count = 0; count < len; count++) {
	120	char c;
	121
	122	/*
	123	* Only read source character once, in case it is
	124	* modified concurrently.
	125	*/
	126	c = CMM_LOAD_SHARED(src[count]);
	127	if (!c)
	128	break;
	129	lib_ring_buffer_do_copy(config, &dest[count], &c, 1);
	130	}
	131	return count;
	132	}
	133
	134	/**
	135	* lib_ring_buffer_strcpy - write string data to a buffer backend
	136	* @config : ring buffer instance configuration
	137	* @ctx: ring buffer context. (input arguments only)
	138	* @src : source pointer to copy from
	139	* @len : length of data to copy
	140	* @pad : character to use for padding
	141	*
	142	* This function copies @len - 1 bytes of string data from a source
	143	* pointer to a buffer backend, followed by a terminating '\0'
	144	* character, at the current context offset. This is more or less a
	145	* buffer backend-specific strncpy() operation. If a terminating '\0'
	146	* character is found in @src before @len - 1 characters are copied, pad
	147	* the buffer with @pad characters (e.g. '#').
	148	*/
	149	static inline
	150	void lib_ring_buffer_strcpy(const struct lttng_ust_lib_ring_buffer_config *config,
	151	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	152	const char *src, size_t len, int pad)
	153	{
	154	struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
	155	struct channel_backend *chanb = &ctx->chan->backend;
	156	struct lttng_ust_shm_handle *handle = ctx->handle;
	157	size_t sbidx, count;
	158	size_t offset = ctx->buf_offset;
	159	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
	160	unsigned long sb_bindex, id;
	161
	162	if (caa_unlikely(!len))
	163	return;
	164	offset &= chanb->buf_size - 1;
	165	sbidx = offset >> chanb->subbuf_size_order;
	166	id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
	167	sb_bindex = subbuffer_id_get_index(config, id);
	168	rpages = shmp_index(handle, bufb->array, sb_bindex);
	169	CHAN_WARN_ON(ctx->chan,
	170	config->mode == RING_BUFFER_OVERWRITE
	171	&& subbuffer_id_is_noref(config, id));
172	/*
173	* Underlying layer should never ask for writes across
174	* subbuffers.
175	*/
176	CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
177	count = lib_ring_buffer_do_strcpy(config,
178	shmp_index(handle, shmp(handle, rpages->shmp)->p,
179	offset & (chanb->subbuf_size - 1)),
180	src, len - 1);
181	offset += count;
182	/* Padding */
183	if (caa_unlikely(count < len - 1)) {
184	size_t pad_len = len - 1 - count;
185
186	lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,
187	offset & (chanb->subbuf_size - 1)),
188	pad, pad_len);
189	offset += pad_len;
190	}
191	/* Final '\0' */
192	lib_ring_buffer_do_memset(shmp_index(handle, shmp(handle, rpages->shmp)->p,
193	offset & (chanb->subbuf_size - 1)),
194	'\0', 1);
195	ctx->buf_offset += len;
196	}
197
852c2936 MD	198	/*
	199	* This accessor counts the number of unread records in a buffer.
	200	* It only provides a consistent value if no reads not writes are performed
	201	* concurrently.
	202	*/
	203	static inline
	204	unsigned long lib_ring_buffer_get_records_unread(
4cfec15c MD	205	const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	206	struct lttng_ust_lib_ring_buffer *buf,
38fae1d3	207	struct lttng_ust_shm_handle *handle)
852c2936	208	{
4cfec15c MD	209	struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
4cfec15c MD	210	struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages;
852c2936 MD	211	unsigned long records_unread = 0, sb_bindex, id;
	212	unsigned int i;
	213
1d498196	214	for (i = 0; i < shmp(handle, bufb->chan)->backend.num_subbuf; i++) {
4746ae29	215	id = shmp_index(handle, bufb->buf_wsb, i)->id;
852c2936	216	sb_bindex = subbuffer_id_get_index(config, id);
4746ae29	217	pages = shmp_index(handle, bufb->array, sb_bindex);
1d498196	218	records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread);
852c2936 MD	219	}
	220	if (config->mode == RING_BUFFER_OVERWRITE) {
	221	id = bufb->buf_rsb.id;
	222	sb_bindex = subbuffer_id_get_index(config, id);
4746ae29	223	pages = shmp_index(handle, bufb->array, sb_bindex);
1d498196	224	records_unread += v_read(config, &shmp(handle, pages->shmp)->records_unread);
852c2936 MD	225	}
	226	return records_unread;
	227	}
	228
e92f3e28	229	#endif /* _LTTNG_RING_BUFFER_BACKEND_H */