[lttng-modules.git] / lib / ringbuffer / backend_internal.h

#ifndef _LIB_RING_BUFFER_BACKEND_INTERNAL_H
#define _LIB_RING_BUFFER_BACKEND_INTERNAL_H

/*
 * lib/ringbuffer/backend_internal.h
 *
 * Ring buffer backend (internal helpers).
 *
 * Copyright (C) 2008-2012 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
 */

#include <wrapper/ringbuffer/config.h>
#include <wrapper/ringbuffer/backend_types.h>
#include <wrapper/ringbuffer/frontend_types.h>
#include <linux/string.h>
#include <linux/uaccess.h>

/* Ring buffer backend API presented to the frontend */

/* Ring buffer and channel backend create/free */

int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb,
				   struct channel_backend *chan, int cpu);
void channel_backend_unregister_notifiers(struct channel_backend *chanb);
void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb);
int channel_backend_init(struct channel_backend *chanb,
			 const char *name,
			 const struct lib_ring_buffer_config *config,
			 void *priv, size_t subbuf_size,
			 size_t num_subbuf);
void channel_backend_free(struct channel_backend *chanb);

void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb);
void channel_backend_reset(struct channel_backend *chanb);

int lib_ring_buffer_backend_init(void);
void lib_ring_buffer_backend_exit(void);

extern void _lib_ring_buffer_write(struct lib_ring_buffer_backend *bufb,
				   size_t offset, const void *src, size_t len,
				   size_t pagecpy);
extern void _lib_ring_buffer_memset(struct lib_ring_buffer_backend *bufb,
				    size_t offset, int c, size_t len,
				    size_t pagecpy);
extern void _lib_ring_buffer_strcpy(struct lib_ring_buffer_backend *bufb,
				   size_t offset, const char *src, size_t len,
				   size_t pagecpy, int pad);
extern void _lib_ring_buffer_copy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
					    size_t offset, const void *src,
					    size_t len, size_t pagecpy);
extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
		size_t offset, const char __user *src, size_t len,
		size_t pagecpy, int pad);

/*
 * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be
 * exchanged atomically.
 *
 * Top half word, except lowest bit, belongs to "offset", which is used to keep
 * to count the produced buffers.  For overwrite mode, this provides the
 * consumer with the capacity to read subbuffers in order, handling the
 * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit
 * systems) concurrently with a single execution of get_subbuf (between offset
 * sampling and subbuffer ID exchange).
 */

#define HALF_ULONG_BITS		(BITS_PER_LONG >> 1)

#define SB_ID_OFFSET_SHIFT	(HALF_ULONG_BITS + 1)
#define SB_ID_OFFSET_COUNT	(1UL << SB_ID_OFFSET_SHIFT)
#define SB_ID_OFFSET_MASK	(~(SB_ID_OFFSET_COUNT - 1))
/*
 * Lowest bit of top word half belongs to noref. Used only for overwrite mode.
 */
#define SB_ID_NOREF_SHIFT	(SB_ID_OFFSET_SHIFT - 1)
#define SB_ID_NOREF_COUNT	(1UL << SB_ID_NOREF_SHIFT)
#define SB_ID_NOREF_MASK	SB_ID_NOREF_COUNT
/*
 * In overwrite mode: lowest half of word is used for index.
 * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit.
 * In producer-consumer mode: whole word used for index.
 */
#define SB_ID_INDEX_SHIFT	0
#define SB_ID_INDEX_COUNT	(1UL << SB_ID_INDEX_SHIFT)
#define SB_ID_INDEX_MASK	(SB_ID_NOREF_COUNT - 1)

/*
 * Construct the subbuffer id from offset, index and noref. Use only the index
 * for producer-consumer mode (offset and noref are only used in overwrite
 * mode).
 */
static inline
unsigned long subbuffer_id(const struct lib_ring_buffer_config *config,
			   unsigned long offset, unsigned long noref,
			   unsigned long index)
{
	if (config->mode == RING_BUFFER_OVERWRITE)
		return (offset << SB_ID_OFFSET_SHIFT)
		       | (noref << SB_ID_NOREF_SHIFT)
		       | index;
	else
		return index;
}

/*
 * Compare offset with the offset contained within id. Return 1 if the offset
 * bits are identical, else 0.
 */
static inline
int subbuffer_id_compare_offset(const struct lib_ring_buffer_config *config,
				unsigned long id, unsigned long offset)
{
	return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT);
}

static inline
unsigned long subbuffer_id_get_index(const struct lib_ring_buffer_config *config,
				     unsigned long id)
{
	if (config->mode == RING_BUFFER_OVERWRITE)
		return id & SB_ID_INDEX_MASK;
	else
		return id;
}

static inline
unsigned long subbuffer_id_is_noref(const struct lib_ring_buffer_config *config,
				    unsigned long id)
{
	if (config->mode == RING_BUFFER_OVERWRITE)
		return !!(id & SB_ID_NOREF_MASK);
	else
		return 1;
}

/*
 * Only used by reader on subbuffer ID it has exclusive access to. No volatile
 * needed.
 */
static inline
void subbuffer_id_set_noref(const struct lib_ring_buffer_config *config,
			    unsigned long *id)
{
	if (config->mode == RING_BUFFER_OVERWRITE)
		*id |= SB_ID_NOREF_MASK;
}

static inline
void subbuffer_id_set_noref_offset(const struct lib_ring_buffer_config *config,
				   unsigned long *id, unsigned long offset)
{
	unsigned long tmp;

	if (config->mode == RING_BUFFER_OVERWRITE) {
		tmp = *id;
		tmp &= ~SB_ID_OFFSET_MASK;
		tmp |= offset << SB_ID_OFFSET_SHIFT;
		tmp |= SB_ID_NOREF_MASK;
		/* Volatile store, read concurrently by readers. */
		ACCESS_ONCE(*id) = tmp;
	}
}

/* No volatile access, since already used locally */
static inline
void subbuffer_id_clear_noref(const struct lib_ring_buffer_config *config,
			      unsigned long *id)
{
	if (config->mode == RING_BUFFER_OVERWRITE)
		*id &= ~SB_ID_NOREF_MASK;
}

/*
 * For overwrite mode, cap the number of subbuffers per buffer to:
 * 2^16 on 32-bit architectures
 * 2^32 on 64-bit architectures
 * This is required to fit in the index part of the ID. Return 0 on success,
 * -EPERM on failure.
 */
static inline
int subbuffer_id_check_index(const struct lib_ring_buffer_config *config,
			     unsigned long num_subbuf)
{
	if (config->mode == RING_BUFFER_OVERWRITE)
		return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0;
	else
		return 0;
}

/*
 * The ring buffer can count events recorded and overwritten per buffer,
 * but it is disabled by default due to its performance overhead.
 */
#ifdef LTTNG_RING_BUFFER_COUNT_EVENTS
static inline
void subbuffer_count_record(const struct lib_ring_buffer_config *config,
			    struct lib_ring_buffer_backend *bufb,
			    unsigned long idx)
{
	unsigned long sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	v_inc(config, &bufb->array[sb_bindex]->records_commit);
}
#else /* LTTNG_RING_BUFFER_COUNT_EVENTS */
static inline
void subbuffer_count_record(const struct lib_ring_buffer_config *config,
			    struct lib_ring_buffer_backend *bufb,
			    unsigned long idx)
{
}
#endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */

/*
 * Reader has exclusive subbuffer access for record consumption. No need to
 * perform the decrement atomically.
 */
static inline
void subbuffer_consume_record(const struct lib_ring_buffer_config *config,
			      struct lib_ring_buffer_backend *bufb)
{
	unsigned long sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
	CHAN_WARN_ON(bufb->chan,
		     !v_read(config, &bufb->array[sb_bindex]->records_unread));
	/* Non-atomic decrement protected by exclusive subbuffer access */
	_v_dec(config, &bufb->array[sb_bindex]->records_unread);
	v_inc(config, &bufb->records_read);
}

static inline
unsigned long subbuffer_get_records_count(
				const struct lib_ring_buffer_config *config,
				struct lib_ring_buffer_backend *bufb,
				unsigned long idx)
{
	unsigned long sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	return v_read(config, &bufb->array[sb_bindex]->records_commit);
}

/*
 * Must be executed at subbuffer delivery when the writer has _exclusive_
 * subbuffer access. See lib_ring_buffer_check_deliver() for details.
 * lib_ring_buffer_get_records_count() must be called to get the records
 * count before this function, because it resets the records_commit
 * count.
 */
static inline
unsigned long subbuffer_count_records_overrun(
				const struct lib_ring_buffer_config *config,
				struct lib_ring_buffer_backend *bufb,
				unsigned long idx)
{
	struct lib_ring_buffer_backend_pages *pages;
	unsigned long overruns, sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	pages = bufb->array[sb_bindex];
	overruns = v_read(config, &pages->records_unread);
	v_set(config, &pages->records_unread,
	      v_read(config, &pages->records_commit));
	v_set(config, &pages->records_commit, 0);

	return overruns;
}

static inline
void subbuffer_set_data_size(const struct lib_ring_buffer_config *config,
			     struct lib_ring_buffer_backend *bufb,
			     unsigned long idx,
			     unsigned long data_size)
{
	struct lib_ring_buffer_backend_pages *pages;
	unsigned long sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	pages = bufb->array[sb_bindex];
	pages->data_size = data_size;
}

static inline
unsigned long subbuffer_get_read_data_size(
				const struct lib_ring_buffer_config *config,
				struct lib_ring_buffer_backend *bufb)
{
	struct lib_ring_buffer_backend_pages *pages;
	unsigned long sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
	pages = bufb->array[sb_bindex];
	return pages->data_size;
}

static inline
unsigned long subbuffer_get_data_size(
				const struct lib_ring_buffer_config *config,
				struct lib_ring_buffer_backend *bufb,
				unsigned long idx)
{
	struct lib_ring_buffer_backend_pages *pages;
	unsigned long sb_bindex;

	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	pages = bufb->array[sb_bindex];
	return pages->data_size;
}

static inline
void subbuffer_inc_packet_count(const struct lib_ring_buffer_config *config,
				struct lib_ring_buffer_backend *bufb,
				unsigned long idx)
{
	bufb->buf_cnt[idx].seq_cnt++;
}

/**
 * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by
 *                               writer.
 */
static inline
void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config,
				 struct lib_ring_buffer_backend *bufb,
				 unsigned long idx)
{
	unsigned long id, new_id;

	if (config->mode != RING_BUFFER_OVERWRITE)
		return;

	/*
	 * Performing a volatile access to read the sb_pages, because we want to
	 * read a coherent version of the pointer and the associated noref flag.
	 */
	id = ACCESS_ONCE(bufb->buf_wsb[idx].id);
	for (;;) {
		/* This check is called on the fast path for each record. */
		if (likely(!subbuffer_id_is_noref(config, id))) {
			/*
			 * Store after load dependency ordering the writes to
			 * the subbuffer after load and test of the noref flag
			 * matches the memory barrier implied by the cmpxchg()
			 * in update_read_sb_index().
			 */
			return;	/* Already writing to this buffer */
		}
		new_id = id;
		subbuffer_id_clear_noref(config, &new_id);
		new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id);
		if (likely(new_id == id))
			break;
		id = new_id;
	}
}

/**
 * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset,
 *                                    called by writer.
 */
static inline
void lib_ring_buffer_set_noref_offset(const struct lib_ring_buffer_config *config,
				      struct lib_ring_buffer_backend *bufb,
				      unsigned long idx, unsigned long offset)
{
	if (config->mode != RING_BUFFER_OVERWRITE)
		return;

	/*
	 * Because ring_buffer_set_noref() is only called by a single thread
	 * (the one which updated the cc_sb value), there are no concurrent
	 * updates to take care of: other writers have not updated cc_sb, so
	 * they cannot set the noref flag, and concurrent readers cannot modify
	 * the pointer because the noref flag is not set yet.
	 * The smp_wmb() in ring_buffer_commit() takes care of ordering writes
	 * to the subbuffer before this set noref operation.
	 * subbuffer_set_noref() uses a volatile store to deal with concurrent
	 * readers of the noref flag.
	 */
	CHAN_WARN_ON(bufb->chan,
		     subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id));
	/*
	 * Memory barrier that ensures counter stores are ordered before set
	 * noref and offset.
	 */
	smp_mb();
	subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset);
}

/**
 * update_read_sb_index - Read-side subbuffer index update.
 */
static inline
int update_read_sb_index(const struct lib_ring_buffer_config *config,
			 struct lib_ring_buffer_backend *bufb,
			 struct channel_backend *chanb,
			 unsigned long consumed_idx,
			 unsigned long consumed_count)
{
	unsigned long old_id, new_id;

	if (config->mode == RING_BUFFER_OVERWRITE) {
		/*
		 * Exchange the target writer subbuffer with our own unused
		 * subbuffer. No need to use ACCESS_ONCE() here to read the
		 * old_wpage, because the value read will be confirmed by the
		 * following cmpxchg().
		 */
		old_id = bufb->buf_wsb[consumed_idx].id;
		if (unlikely(!subbuffer_id_is_noref(config, old_id)))
			return -EAGAIN;
		/*
		 * Make sure the offset count we are expecting matches the one
		 * indicated by the writer.
		 */
		if (unlikely(!subbuffer_id_compare_offset(config, old_id,
							  consumed_count)))
			return -EAGAIN;
		CHAN_WARN_ON(bufb->chan,
			     !subbuffer_id_is_noref(config, bufb->buf_rsb.id));
		subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id,
					      consumed_count);
		new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id,
				 bufb->buf_rsb.id);
		if (unlikely(old_id != new_id))
			return -EAGAIN;
		bufb->buf_rsb.id = new_id;
	} else {
		/* No page exchange, use the writer page directly */
		bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id;
	}
	return 0;
}

/*
 * Use the architecture-specific memcpy implementation for constant-sized
 * inputs, but rely on an inline memcpy for length statically unknown.
 * The function call to memcpy is just way too expensive for a fast path.
 */
#define lib_ring_buffer_do_copy(config, dest, src, len)		\
do {								\
	size_t __len = (len);					\
	if (__builtin_constant_p(len))				\
		memcpy(dest, src, __len);			\
	else							\
		inline_memcpy(dest, src, __len);		\
} while (0)

/*
 * We use __copy_from_user_inatomic to copy userspace data since we already
 * did the access_ok for the whole range.
 *
 * Return 0 if OK, nonzero on error.
 */
static inline
unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest,
						const void __user *src,
						unsigned long len)
{
	return __copy_from_user_inatomic(dest, src, len);
}

/*
 * write len bytes to dest with c
 */
static inline
void lib_ring_buffer_do_memset(char *dest, int c,
	unsigned long len)
{
	unsigned long i;

	for (i = 0; i < len; i++)
		dest[i] = c;
}

#endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */
Commit	Line	Data
886d51a3 MD	1	#ifndef _LIB_RING_BUFFER_BACKEND_INTERNAL_H
886d51a3 MD	2	#define _LIB_RING_BUFFER_BACKEND_INTERNAL_H
f3bc08c5 MD	3
f3bc08c5 MD	4	/*
886d51a3	5	* lib/ringbuffer/backend_internal.h
f3bc08c5 MD	6	*
	7	* Ring buffer backend (internal helpers).
	8	*
886d51a3 MD	9	* Copyright (C) 2008-2012 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
f3bc08c5 MD	24	*/
f3bc08c5 MD	25
5671a661 MD	26	#include <wrapper/ringbuffer/config.h>
	27	#include <wrapper/ringbuffer/backend_types.h>
	28	#include <wrapper/ringbuffer/frontend_types.h>
f3bc08c5	29	#include <linux/string.h>
4ea00e4f	30	#include <linux/uaccess.h>
f3bc08c5 MD	31
	32	/* Ring buffer backend API presented to the frontend */
	33
	34	/* Ring buffer and channel backend create/free */
	35
	36	int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb,
	37	struct channel_backend *chan, int cpu);
	38	void channel_backend_unregister_notifiers(struct channel_backend *chanb);
	39	void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb);
	40	int channel_backend_init(struct channel_backend *chanb,
	41	const char *name,
	42	const struct lib_ring_buffer_config *config,
	43	void *priv, size_t subbuf_size,
	44	size_t num_subbuf);
	45	void channel_backend_free(struct channel_backend *chanb);
	46
	47	void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb);
	48	void channel_backend_reset(struct channel_backend *chanb);
	49
	50	int lib_ring_buffer_backend_init(void);
	51	void lib_ring_buffer_backend_exit(void);
	52
	53	extern void _lib_ring_buffer_write(struct lib_ring_buffer_backend *bufb,
	54	size_t offset, const void *src, size_t len,
bfe529f9	55	size_t pagecpy);
4ea00e4f JD	56	extern void _lib_ring_buffer_memset(struct lib_ring_buffer_backend *bufb,
4ea00e4f JD	57	size_t offset, int c, size_t len,
bfe529f9	58	size_t pagecpy);
16f78f3a MD	59	extern void _lib_ring_buffer_strcpy(struct lib_ring_buffer_backend *bufb,
	60	size_t offset, const char *src, size_t len,
	61	size_t pagecpy, int pad);
7b8ea3a5	62	extern void _lib_ring_buffer_copy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
4ea00e4f	63	size_t offset, const void *src,
bfe529f9	64	size_t len, size_t pagecpy);
16f78f3a MD	65	extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lib_ring_buffer_backend *bufb,
	66	size_t offset, const char __user *src, size_t len,
	67	size_t pagecpy, int pad);
f3bc08c5 MD	68
	69	/*
	70	* Subbuffer ID bits for overwrite mode. Need to fit within a single word to be
	71	* exchanged atomically.
	72	*
	73	* Top half word, except lowest bit, belongs to "offset", which is used to keep
	74	* to count the produced buffers. For overwrite mode, this provides the
	75	* consumer with the capacity to read subbuffers in order, handling the
	76	* situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit
	77	* systems) concurrently with a single execution of get_subbuf (between offset
	78	* sampling and subbuffer ID exchange).
	79	*/
	80
	81	#define HALF_ULONG_BITS (BITS_PER_LONG >> 1)
	82
	83	#define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1)
	84	#define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT)
	85	#define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1))
	86	/*
	87	* Lowest bit of top word half belongs to noref. Used only for overwrite mode.
	88	*/
	89	#define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1)
	90	#define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT)
	91	#define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT
	92	/*
	93	* In overwrite mode: lowest half of word is used for index.
	94	* Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit.
	95	* In producer-consumer mode: whole word used for index.
	96	*/
	97	#define SB_ID_INDEX_SHIFT 0
	98	#define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT)
	99	#define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1)
	100
	101	/*
	102	* Construct the subbuffer id from offset, index and noref. Use only the index
	103	* for producer-consumer mode (offset and noref are only used in overwrite
	104	* mode).
	105	*/
	106	static inline
	107	unsigned long subbuffer_id(const struct lib_ring_buffer_config *config,
	108	unsigned long offset, unsigned long noref,
	109	unsigned long index)
	110	{
	111	if (config->mode == RING_BUFFER_OVERWRITE)
	112	return (offset << SB_ID_OFFSET_SHIFT)
	113	\| (noref << SB_ID_NOREF_SHIFT)
	114	\| index;
	115	else
	116	return index;
	117	}
	118
	119	/*
	120	* Compare offset with the offset contained within id. Return 1 if the offset
	121	* bits are identical, else 0.
	122	*/
	123	static inline
	124	int subbuffer_id_compare_offset(const struct lib_ring_buffer_config *config,
	125	unsigned long id, unsigned long offset)
	126	{
	127	return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT);
	128	}
	129
	130	static inline
	131	unsigned long subbuffer_id_get_index(const struct lib_ring_buffer_config *config,
132	unsigned long id)
133	{
134	if (config->mode == RING_BUFFER_OVERWRITE)
135	return id & SB_ID_INDEX_MASK;
136	else
137	return id;
138	}
139
140	static inline
141	unsigned long subbuffer_id_is_noref(const struct lib_ring_buffer_config *config,
142	unsigned long id)
143	{
144	if (config->mode == RING_BUFFER_OVERWRITE)
145	return !!(id & SB_ID_NOREF_MASK);
146	else
147	return 1;
148	}
149
150	/*
151	* Only used by reader on subbuffer ID it has exclusive access to. No volatile
152	* needed.
153	*/
154	static inline
155	void subbuffer_id_set_noref(const struct lib_ring_buffer_config *config,
156	unsigned long *id)
157	{
158	if (config->mode == RING_BUFFER_OVERWRITE)
159	*id \|= SB_ID_NOREF_MASK;
160	}
161
162	static inline
163	void subbuffer_id_set_noref_offset(const struct lib_ring_buffer_config *config,
164	unsigned long *id, unsigned long offset)
165	{
166	unsigned long tmp;
167
168	if (config->mode == RING_BUFFER_OVERWRITE) {
169	tmp = *id;
170	tmp &= ~SB_ID_OFFSET_MASK;
171	tmp \|= offset << SB_ID_OFFSET_SHIFT;
172	tmp \|= SB_ID_NOREF_MASK;
173	/* Volatile store, read concurrently by readers. */
174	ACCESS_ONCE(*id) = tmp;
175	}
176	}
177
178	/* No volatile access, since already used locally */
179	static inline
180	void subbuffer_id_clear_noref(const struct lib_ring_buffer_config *config,
181	unsigned long *id)
182	{
183	if (config->mode == RING_BUFFER_OVERWRITE)
184	*id &= ~SB_ID_NOREF_MASK;
185	}
186
187	/*
188	* For overwrite mode, cap the number of subbuffers per buffer to:
189	* 2^16 on 32-bit architectures
190	* 2^32 on 64-bit architectures
191	* This is required to fit in the index part of the ID. Return 0 on success,
192	* -EPERM on failure.
193	*/
194	static inline
195	int subbuffer_id_check_index(const struct lib_ring_buffer_config *config,
196	unsigned long num_subbuf)
197	{
198	if (config->mode == RING_BUFFER_OVERWRITE)
199	return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0;
200	else
201	return 0;
202	}
203
25337cb5 MD	204	/*
	205	* The ring buffer can count events recorded and overwritten per buffer,
	206	* but it is disabled by default due to its performance overhead.
	207	*/
	208	#ifdef LTTNG_RING_BUFFER_COUNT_EVENTS
f3bc08c5 MD	209	static inline
	210	void subbuffer_count_record(const struct lib_ring_buffer_config *config,
	211	struct lib_ring_buffer_backend *bufb,
	212	unsigned long idx)
	213	{
	214	unsigned long sb_bindex;
	215
	216	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	217	v_inc(config, &bufb->array[sb_bindex]->records_commit);
	218	}
25337cb5 MD	219	#else /* LTTNG_RING_BUFFER_COUNT_EVENTS */
	220	static inline
	221	void subbuffer_count_record(const struct lib_ring_buffer_config *config,
	222	struct lib_ring_buffer_backend *bufb,
	223	unsigned long idx)
	224	{
	225	}
	226	#endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */
f3bc08c5 MD	227
	228	/*
	229	* Reader has exclusive subbuffer access for record consumption. No need to
	230	* perform the decrement atomically.
	231	*/
	232	static inline
	233	void subbuffer_consume_record(const struct lib_ring_buffer_config *config,
	234	struct lib_ring_buffer_backend *bufb)
	235	{
	236	unsigned long sb_bindex;
	237
	238	sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
	239	CHAN_WARN_ON(bufb->chan,
	240	!v_read(config, &bufb->array[sb_bindex]->records_unread));
	241	/* Non-atomic decrement protected by exclusive subbuffer access */
	242	_v_dec(config, &bufb->array[sb_bindex]->records_unread);
	243	v_inc(config, &bufb->records_read);
	244	}
	245
	246	static inline
	247	unsigned long subbuffer_get_records_count(
	248	const struct lib_ring_buffer_config *config,
	249	struct lib_ring_buffer_backend *bufb,
	250	unsigned long idx)
	251	{
	252	unsigned long sb_bindex;
	253
	254	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	255	return v_read(config, &bufb->array[sb_bindex]->records_commit);
	256	}
	257
	258	/*
	259	* Must be executed at subbuffer delivery when the writer has _exclusive_
c68be968 MD	260	* subbuffer access. See lib_ring_buffer_check_deliver() for details.
	261	* lib_ring_buffer_get_records_count() must be called to get the records
	262	* count before this function, because it resets the records_commit
	263	* count.
f3bc08c5 MD	264	*/
	265	static inline
	266	unsigned long subbuffer_count_records_overrun(
	267	const struct lib_ring_buffer_config *config,
	268	struct lib_ring_buffer_backend *bufb,
	269	unsigned long idx)
	270	{
	271	struct lib_ring_buffer_backend_pages *pages;
	272	unsigned long overruns, sb_bindex;
	273
	274	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	275	pages = bufb->array[sb_bindex];
	276	overruns = v_read(config, &pages->records_unread);
	277	v_set(config, &pages->records_unread,
	278	v_read(config, &pages->records_commit));
	279	v_set(config, &pages->records_commit, 0);
	280
	281	return overruns;
	282	}
	283
	284	static inline
	285	void subbuffer_set_data_size(const struct lib_ring_buffer_config *config,
	286	struct lib_ring_buffer_backend *bufb,
	287	unsigned long idx,
	288	unsigned long data_size)
	289	{
	290	struct lib_ring_buffer_backend_pages *pages;
	291	unsigned long sb_bindex;
	292
	293	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	294	pages = bufb->array[sb_bindex];
	295	pages->data_size = data_size;
	296	}
	297
	298	static inline
	299	unsigned long subbuffer_get_read_data_size(
	300	const struct lib_ring_buffer_config *config,
	301	struct lib_ring_buffer_backend *bufb)
	302	{
	303	struct lib_ring_buffer_backend_pages *pages;
	304	unsigned long sb_bindex;
	305
	306	sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
	307	pages = bufb->array[sb_bindex];
	308	return pages->data_size;
	309	}
	310
	311	static inline
	312	unsigned long subbuffer_get_data_size(
	313	const struct lib_ring_buffer_config *config,
	314	struct lib_ring_buffer_backend *bufb,
	315	unsigned long idx)
	316	{
	317	struct lib_ring_buffer_backend_pages *pages;
	318	unsigned long sb_bindex;
	319
	320	sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id);
	321	pages = bufb->array[sb_bindex];
	322	return pages->data_size;
	323	}
	324
5b3cf4f9 JD	325	static inline
	326	void subbuffer_inc_packet_count(const struct lib_ring_buffer_config *config,
	327	struct lib_ring_buffer_backend *bufb,
	328	unsigned long idx)
	329	{
	330	bufb->buf_cnt[idx].seq_cnt++;
	331	}
	332
f3bc08c5 MD	333	/**
	334	* lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by
	335	* writer.
	336	*/
	337	static inline
	338	void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config,
	339	struct lib_ring_buffer_backend *bufb,
	340	unsigned long idx)
	341	{
	342	unsigned long id, new_id;
	343
	344	if (config->mode != RING_BUFFER_OVERWRITE)
	345	return;
	346
	347	/*
	348	* Performing a volatile access to read the sb_pages, because we want to
	349	* read a coherent version of the pointer and the associated noref flag.
	350	*/
	351	id = ACCESS_ONCE(bufb->buf_wsb[idx].id);
	352	for (;;) {
	353	/* This check is called on the fast path for each record. */
	354	if (likely(!subbuffer_id_is_noref(config, id))) {
	355	/*
	356	* Store after load dependency ordering the writes to
	357	* the subbuffer after load and test of the noref flag
	358	* matches the memory barrier implied by the cmpxchg()
	359	* in update_read_sb_index().
	360	*/
	361	return; /* Already writing to this buffer */
	362	}
	363	new_id = id;
	364	subbuffer_id_clear_noref(config, &new_id);
	365	new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id);
	366	if (likely(new_id == id))
	367	break;
	368	id = new_id;
	369	}
	370	}
	371
	372	/**
	373	* lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset,
	374	* called by writer.
	375	*/
	376	static inline
	377	void lib_ring_buffer_set_noref_offset(const struct lib_ring_buffer_config *config,
	378	struct lib_ring_buffer_backend *bufb,
	379	unsigned long idx, unsigned long offset)
	380	{
	381	if (config->mode != RING_BUFFER_OVERWRITE)
	382	return;
	383
	384	/*
	385	* Because ring_buffer_set_noref() is only called by a single thread
	386	* (the one which updated the cc_sb value), there are no concurrent
	387	* updates to take care of: other writers have not updated cc_sb, so
	388	* they cannot set the noref flag, and concurrent readers cannot modify
	389	* the pointer because the noref flag is not set yet.
	390	* The smp_wmb() in ring_buffer_commit() takes care of ordering writes
	391	* to the subbuffer before this set noref operation.
	392	* subbuffer_set_noref() uses a volatile store to deal with concurrent
	393	* readers of the noref flag.
	394	*/
	395	CHAN_WARN_ON(bufb->chan,
	396	subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id));
397	/*
398	* Memory barrier that ensures counter stores are ordered before set
399	* noref and offset.
400	*/
401	smp_mb();
402	subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset);
403	}
404
405	/**
406	* update_read_sb_index - Read-side subbuffer index update.
407	*/
408	static inline
409	int update_read_sb_index(const struct lib_ring_buffer_config *config,
410	struct lib_ring_buffer_backend *bufb,
411	struct channel_backend *chanb,
412	unsigned long consumed_idx,
413	unsigned long consumed_count)
414	{
415	unsigned long old_id, new_id;
416
417	if (config->mode == RING_BUFFER_OVERWRITE) {
418	/*
419	* Exchange the target writer subbuffer with our own unused
420	* subbuffer. No need to use ACCESS_ONCE() here to read the
421	* old_wpage, because the value read will be confirmed by the
422	* following cmpxchg().
423	*/
424	old_id = bufb->buf_wsb[consumed_idx].id;
425	if (unlikely(!subbuffer_id_is_noref(config, old_id)))
426	return -EAGAIN;
427	/*
428	* Make sure the offset count we are expecting matches the one
429	* indicated by the writer.
430	*/
431	if (unlikely(!subbuffer_id_compare_offset(config, old_id,
432	consumed_count)))
433	return -EAGAIN;
434	CHAN_WARN_ON(bufb->chan,
435	!subbuffer_id_is_noref(config, bufb->buf_rsb.id));
436	subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id,
437	consumed_count);
438	new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id,
439	bufb->buf_rsb.id);
440	if (unlikely(old_id != new_id))
441	return -EAGAIN;
442	bufb->buf_rsb.id = new_id;
443	} else {
444	/* No page exchange, use the writer page directly */
445	bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id;
446	}
447	return 0;
448	}
449
450	/*
451	* Use the architecture-specific memcpy implementation for constant-sized
452	* inputs, but rely on an inline memcpy for length statically unknown.
453	* The function call to memcpy is just way too expensive for a fast path.
454	*/
455	#define lib_ring_buffer_do_copy(config, dest, src, len) \
456	do { \
457	size_t __len = (len); \
458	if (__builtin_constant_p(len)) \
459	memcpy(dest, src, __len); \
460	else \
461	inline_memcpy(dest, src, __len); \
462	} while (0)
463
4ea00e4f	464	/*
7b8ea3a5	465	* We use __copy_from_user_inatomic to copy userspace data since we already
4ea00e4f	466	* did the access_ok for the whole range.
d87a9f03 MD	467	*
d87a9f03 MD	468	* Return 0 if OK, nonzero on error.
4ea00e4f JD	469	*/
4ea00e4f JD	470	static inline
7b8ea3a5	471	unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest,
4ea00e4f JD	472	const void __user *src,
	473	unsigned long len)
	474	{
7b8ea3a5	475	return __copy_from_user_inatomic(dest, src, len);
4ea00e4f JD	476	}
	477
	478	/*
	479	* write len bytes to dest with c
	480	*/
	481	static inline
	482	void lib_ring_buffer_do_memset(char *dest, int c,
	483	unsigned long len)
	484	{
	485	unsigned long i;
	486
	487	for (i = 0; i < len; i++)
	488	dest[i] = c;
	489	}
	490
886d51a3	491	#endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */