[lttng-modules.git] / include / ringbuffer / config.h

/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
 *
 * ringbuffer/config.h
 *
 * Ring buffer configuration header. Note: after declaring the standard inline
 * functions, clients should also include linux/ringbuffer/api.h.
 *
 * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#ifndef _LIB_RING_BUFFER_CONFIG_H
#define _LIB_RING_BUFFER_CONFIG_H

#include <linux/types.h>
#include <linux/percpu.h>
#include <lttng/align.h>
#include <lttng/tracer-core.h>

struct lttng_kernel_ring_buffer;
struct lttng_kernel_ring_buffer_channel;
struct lttng_kernel_ring_buffer_config;
struct lttng_kernel_ring_buffer_ctx;
struct lttng_kernel_ring_buffer_ctx_private;

/*
 * Ring buffer client callbacks. Only used by slow path, never on fast path.
 * For the fast path, record_header_size(), ring_buffer_clock_read() should be
 * provided as inline functions too.  These may simply return 0 if not used by
 * the client.
 */
struct lttng_kernel_ring_buffer_client_cb {
	/* Mandatory callbacks */

	/* A static inline version is also required for fast path */
	u64 (*ring_buffer_clock_read) (struct lttng_kernel_ring_buffer_channel *chan);
	size_t (*record_header_size) (const struct lttng_kernel_ring_buffer_config *config,
				      struct lttng_kernel_ring_buffer_channel *chan, size_t offset,
				      size_t *pre_header_padding,
				      struct lttng_kernel_ring_buffer_ctx *ctx,
				      void *client_ctx);

	/* Slow path only, at subbuffer switch */
	size_t (*subbuffer_header_size) (void);
	void (*buffer_begin) (struct lttng_kernel_ring_buffer *buf, u64 tsc,
			      unsigned int subbuf_idx);
	void (*buffer_end) (struct lttng_kernel_ring_buffer *buf, u64 tsc,
			    unsigned int subbuf_idx, unsigned long data_size,
			    const struct lttng_kernel_ring_buffer_ctx *ctx);

	/* Optional callbacks (can be set to NULL) */

	/* Called at buffer creation/finalize */
	int (*buffer_create) (struct lttng_kernel_ring_buffer *buf, void *priv,
			      int cpu, const char *name);
	/*
	 * Clients should guarantee that no new reader handle can be opened
	 * after finalize.
	 */
	void (*buffer_finalize) (struct lttng_kernel_ring_buffer *buf, void *priv, int cpu);

	/*
	 * Extract header length, payload length and timestamp from event
	 * record. Used by buffer iterators. Timestamp is only used by channel
	 * iterator.
	 */
	void (*record_get) (const struct lttng_kernel_ring_buffer_config *config,
			    struct lttng_kernel_ring_buffer_channel *chan, struct lttng_kernel_ring_buffer *buf,
			    size_t offset, size_t *header_len,
			    size_t *payload_len, u64 *timestamp);
};

/*
 * Ring buffer instance configuration.
 *
 * Declare as "static const" within the client object to ensure the inline fast
 * paths can be optimized.
 *
 * alloc/sync pairs:
 *
 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
 *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
 *   with preemption disabled (lib_ring_buffer_get_cpu() and
 *   lib_ring_buffer_put_cpu()).
 *
 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
 *   Per-cpu buffer with global synchronization. Tracing can be performed with
 *   preemption enabled, statistically stays on the local buffers.
 *
 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 *   Should only be used for buffers belonging to a single thread or protected
 *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 *   should be disabled in this kind of configuration.
 *
 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 *   Global shared buffer with global synchronization.
 *
 * wakeup:
 *
 * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the
 * buffers and wake up readers if data is ready. Mainly useful for tracers which
 * don't want to call into the wakeup code on the tracing path. Use in
 * combination with "read_timer_interval" channel_create() argument.
 *
 * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 * for drivers. Going through an "irq_work" allows triggering this type of wakeup
 * even from NMI context: the wakeup will be slightly delayed until the next
 * interrupts are handled.
 *
 * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 * has the responsibility to perform wakeups.
 */
struct lttng_kernel_ring_buffer_config {
	enum {
		RING_BUFFER_ALLOC_PER_CPU,
		RING_BUFFER_ALLOC_GLOBAL,
	} alloc;
	enum {
		RING_BUFFER_SYNC_PER_CPU,	/* Wait-free */
		RING_BUFFER_SYNC_GLOBAL,	/* Lock-free */
	} sync;
	enum {
		RING_BUFFER_OVERWRITE,		/* Overwrite when buffer full */
		RING_BUFFER_DISCARD,		/* Discard when buffer full */
	} mode;
	enum {
		RING_BUFFER_SPLICE,
		RING_BUFFER_MMAP,
		RING_BUFFER_READ,		/* TODO */
		RING_BUFFER_ITERATOR,
		RING_BUFFER_NONE,
	} output;
	enum {
		RING_BUFFER_PAGE,
		RING_BUFFER_VMAP,		/* TODO */
		RING_BUFFER_STATIC,		/* TODO */
	} backend;
	enum {
		RING_BUFFER_NO_OOPS_CONSISTENCY,
		RING_BUFFER_OOPS_CONSISTENCY,
	} oops;
	enum {
		RING_BUFFER_IPI_BARRIER,
		RING_BUFFER_NO_IPI_BARRIER,
	} ipi;
	enum {
		RING_BUFFER_WAKEUP_BY_TIMER,	/* wake up performed by timer */
		RING_BUFFER_WAKEUP_BY_WRITER,	/*
						 * writer wakes up reader through
						 * irq_work.
						 */
	} wakeup;
	/*
	 * tsc_bits: timestamp bits saved at each record.
	 *   0 and 64 disable the timestamp compression scheme.
	 */
	unsigned int tsc_bits;
	struct lttng_kernel_ring_buffer_client_cb cb;
};

/*
 * ring buffer private context
 *
 * Private context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 * lib_ring_buffer_write().
 *
 * Get struct lttng_kernel_ring_buffer_ctx parent with container_of().
 */

struct lttng_kernel_ring_buffer_ctx_private {
	/* input received by lib_ring_buffer_reserve(). */
	struct lttng_kernel_ring_buffer_channel *chan;			/* ring buffer channel */

	/* output from lib_ring_buffer_reserve() */
	int reserve_cpu;			/* processor id updated by the reserve */
	size_t slot_size;			/* size of the reserved slot */
	unsigned long buf_offset;		/* offset following the record header */
	unsigned long pre_offset;		/*
						 * Initial offset position _before_
						 * the record is written. Positioned
						 * prior to record header alignment
						 * padding.
						 */
	u64 tsc;				/* time-stamp counter value */
	unsigned int rflags;			/* reservation flags */

	struct lttng_kernel_ring_buffer *buf;	/*
						 * buffer corresponding to processor id
						 * for this channel
						 */
	struct lttng_kernel_ring_buffer_backend_pages *backend_pages;

	/*
	 * Records lost counts are only loaded into these fields before
	 * reserving the last bytes from the ring buffer.
	 */
	unsigned long records_lost_full;
	unsigned long records_lost_wrap;
	unsigned long records_lost_big;
};

/*
 * ring buffer context
 *
 * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 * lib_ring_buffer_write().
 */
struct lttng_kernel_ring_buffer_ctx {
	/* Private ring buffer context, set by reserve callback. */
	struct lttng_kernel_ring_buffer_ctx_private priv;

	/* input received by lib_ring_buffer_reserve(), saved here. */
	void *client_priv;		/* Ring buffer client private data */

	size_t data_size;		/* size of payload */
	int largest_align;		/*
					 * alignment of the largest element
					 * in the payload
					 */
	struct lttng_kernel_probe_ctx *probe_ctx;	/* Probe context */
};

/**
 * lib_ring_buffer_ctx_init - initialize ring buffer context
 * @ctx: ring buffer context to initialize
 * @client_priv: client private data
 * @data_size: size of record data payload. It must be greater than 0.
 * @largest_align: largest alignment within data payload types
 */
static inline
void lib_ring_buffer_ctx_init(struct lttng_kernel_ring_buffer_ctx *ctx,
			      void *client_priv,
			      size_t data_size, int largest_align,
			      struct lttng_kernel_probe_ctx *probe_ctx)
{
	ctx->client_priv = client_priv;
	ctx->data_size = data_size;
	ctx->largest_align = largest_align;
	ctx->probe_ctx = probe_ctx;
}

/*
 * Reservation flags.
 *
 * RING_BUFFER_RFLAG_FULL_TSC
 *
 * This flag is passed to record_header_size() and to the primitive used to
 * write the record header. It indicates that the full 64-bit time value is
 * needed in the record header. If this flag is not set, the record header needs
 * only to contain "tsc_bits" bit of time value.
 *
 * Reservation flags can be added by the client, starting from
 * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 * record_header_size() to lib_ring_buffer_write_record_header().
 */
#define	RING_BUFFER_RFLAG_FULL_TSC		(1U << 0)
#define RING_BUFFER_RFLAG_END			(1U << 1)

#ifndef LTTNG_TRACER_CORE_H
#error "lttng/tracer-core.h is needed for RING_BUFFER_ALIGN define"
#endif

/*
 * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 * compile-time. We have to duplicate the "config->align" information and the
 * definition here because config->align is used both in the slow and fast
 * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 */
#ifdef RING_BUFFER_ALIGN

# define RING_BUFFER_ALIGN_ATTR		/* Default arch alignment */

/*
 * Calculate the offset needed to align the type.
 * size_of_type must be non-zero.
 */
static inline
unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
{
	return offset_align(align_drift, size_of_type);
}

#else

# define RING_BUFFER_ALIGN_ATTR __attribute__((packed))

/*
 * Calculate the offset needed to align the type.
 * size_of_type must be non-zero.
 */
static inline
unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
{
	return 0;
}

#endif

/**
 * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 * @ctx: ring buffer context.
 */
static inline
void lib_ring_buffer_align_ctx(struct lttng_kernel_ring_buffer_ctx *ctx,
			   size_t alignment)
{
	ctx->priv.buf_offset += lib_ring_buffer_align(ctx->priv.buf_offset,
						 alignment);
}

/*
 * lib_ring_buffer_check_config() returns 0 on success.
 * Used internally to check for valid configurations at channel creation.
 */
static inline
int lib_ring_buffer_check_config(const struct lttng_kernel_ring_buffer_config *config,
			     unsigned int switch_timer_interval,
			     unsigned int read_timer_interval)
{
	if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
	    && config->sync == RING_BUFFER_SYNC_PER_CPU
	    && switch_timer_interval)
		return -EINVAL;
	return 0;
}

#include <ringbuffer/vatomic.h>

#endif /* _LIB_RING_BUFFER_CONFIG_H */
Commit	Line	Data
	1	/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
	2	*
	3	* ringbuffer/config.h
	4	*
	5	* Ring buffer configuration header. Note: after declaring the standard inline
	6	* functions, clients should also include linux/ringbuffer/api.h.
	7	*
	8	* Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	9	*/
	10
	11	#ifndef _LIB_RING_BUFFER_CONFIG_H
	12	#define _LIB_RING_BUFFER_CONFIG_H
	13
	14	#include <linux/types.h>
	15	#include <linux/percpu.h>
	16	#include <lttng/align.h>
	17	#include <lttng/tracer-core.h>
	18
	19	struct lttng_kernel_ring_buffer;
	20	struct lttng_kernel_ring_buffer_channel;
	21	struct lttng_kernel_ring_buffer_config;
	22	struct lttng_kernel_ring_buffer_ctx;
	23	struct lttng_kernel_ring_buffer_ctx_private;
	24
	25	/*
	26	* Ring buffer client callbacks. Only used by slow path, never on fast path.
	27	* For the fast path, record_header_size(), ring_buffer_clock_read() should be
	28	* provided as inline functions too. These may simply return 0 if not used by
	29	* the client.
	30	*/
	31	struct lttng_kernel_ring_buffer_client_cb {
	32	/* Mandatory callbacks */
	33
	34	/* A static inline version is also required for fast path */
	35	u64 (ring_buffer_clock_read) (struct lttng_kernel_ring_buffer_channel chan);
	36	size_t (record_header_size) (const struct lttng_kernel_ring_buffer_config config,
	37	struct lttng_kernel_ring_buffer_channel *chan, size_t offset,
	38	size_t *pre_header_padding,
	39	struct lttng_kernel_ring_buffer_ctx *ctx,
	40	void *client_ctx);
	41
	42	/* Slow path only, at subbuffer switch */
	43	size_t (*subbuffer_header_size) (void);
	44	void (buffer_begin) (struct lttng_kernel_ring_buffer buf, u64 tsc,
	45	unsigned int subbuf_idx);
	46	void (buffer_end) (struct lttng_kernel_ring_buffer buf, u64 tsc,
	47	unsigned int subbuf_idx, unsigned long data_size,
	48	const struct lttng_kernel_ring_buffer_ctx *ctx);
	49
	50	/* Optional callbacks (can be set to NULL) */
	51
	52	/* Called at buffer creation/finalize */
	53	int (buffer_create) (struct lttng_kernel_ring_buffer buf, void *priv,
	54	int cpu, const char *name);
	55	/*
	56	* Clients should guarantee that no new reader handle can be opened
	57	* after finalize.
	58	*/
	59	void (buffer_finalize) (struct lttng_kernel_ring_buffer buf, void *priv, int cpu);
	60
	61	/*
	62	* Extract header length, payload length and timestamp from event
	63	* record. Used by buffer iterators. Timestamp is only used by channel
	64	* iterator.
	65	*/
	66	void (record_get) (const struct lttng_kernel_ring_buffer_config config,
	67	struct lttng_kernel_ring_buffer_channel chan, struct lttng_kernel_ring_buffer buf,
	68	size_t offset, size_t *header_len,
	69	size_t payload_len, u64 timestamp);
	70	};
	71
	72	/*
	73	* Ring buffer instance configuration.
	74	*
	75	* Declare as "static const" within the client object to ensure the inline fast
	76	* paths can be optimized.
	77	*
	78	* alloc/sync pairs:
	79	*
	80	* RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
	81	* Per-cpu buffers with per-cpu synchronization. Tracing must be performed
	82	* with preemption disabled (lib_ring_buffer_get_cpu() and
	83	* lib_ring_buffer_put_cpu()).
	84	*
	85	* RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
	86	* Per-cpu buffer with global synchronization. Tracing can be performed with
	87	* preemption enabled, statistically stays on the local buffers.
	88	*
	89	* RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
	90	* Should only be used for buffers belonging to a single thread or protected
	91	* by mutual exclusion by the client. Note that periodical sub-buffer switch
	92	* should be disabled in this kind of configuration.
	93	*
	94	* RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
	95	* Global shared buffer with global synchronization.
	96	*
	97	* wakeup:
	98	*
	99	* RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the
	100	* buffers and wake up readers if data is ready. Mainly useful for tracers which
	101	* don't want to call into the wakeup code on the tracing path. Use in
	102	* combination with "read_timer_interval" channel_create() argument.
	103	*
	104	* RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
	105	* ready to read. Lower latencies before the reader is woken up. Mainly suitable
	106	* for drivers. Going through an "irq_work" allows triggering this type of wakeup
	107	* even from NMI context: the wakeup will be slightly delayed until the next
	108	* interrupts are handled.
	109	*
	110	* RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
	111	* has the responsibility to perform wakeups.
	112	*/
	113	struct lttng_kernel_ring_buffer_config {
	114	enum {
	115	RING_BUFFER_ALLOC_PER_CPU,
	116	RING_BUFFER_ALLOC_GLOBAL,
	117	} alloc;
	118	enum {
	119	RING_BUFFER_SYNC_PER_CPU, /* Wait-free */
	120	RING_BUFFER_SYNC_GLOBAL, /* Lock-free */
	121	} sync;
	122	enum {
	123	RING_BUFFER_OVERWRITE, /* Overwrite when buffer full */
	124	RING_BUFFER_DISCARD, /* Discard when buffer full */
	125	} mode;
	126	enum {
	127	RING_BUFFER_SPLICE,
	128	RING_BUFFER_MMAP,
	129	RING_BUFFER_READ, /* TODO */
	130	RING_BUFFER_ITERATOR,
	131	RING_BUFFER_NONE,
	132	} output;
	133	enum {
	134	RING_BUFFER_PAGE,
	135	RING_BUFFER_VMAP, /* TODO */
	136	RING_BUFFER_STATIC, /* TODO */
	137	} backend;
	138	enum {
	139	RING_BUFFER_NO_OOPS_CONSISTENCY,
	140	RING_BUFFER_OOPS_CONSISTENCY,
	141	} oops;
	142	enum {
	143	RING_BUFFER_IPI_BARRIER,
	144	RING_BUFFER_NO_IPI_BARRIER,
	145	} ipi;
	146	enum {
	147	RING_BUFFER_WAKEUP_BY_TIMER, /* wake up performed by timer */
	148	RING_BUFFER_WAKEUP_BY_WRITER, /*
	149	* writer wakes up reader through
	150	* irq_work.
	151	*/
	152	} wakeup;
	153	/*
	154	* tsc_bits: timestamp bits saved at each record.
	155	* 0 and 64 disable the timestamp compression scheme.
	156	*/
	157	unsigned int tsc_bits;
	158	struct lttng_kernel_ring_buffer_client_cb cb;
	159	};
	160
	161	/*
	162	* ring buffer private context
	163	*
	164	* Private context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
	165	* lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
	166	* lib_ring_buffer_write().
	167	*
	168	* Get struct lttng_kernel_ring_buffer_ctx parent with container_of().
	169	*/
	170
	171	struct lttng_kernel_ring_buffer_ctx_private {
	172	/* input received by lib_ring_buffer_reserve(). */
	173	struct lttng_kernel_ring_buffer_channel chan; / ring buffer channel */
	174
	175	/* output from lib_ring_buffer_reserve() */
	176	int reserve_cpu; /* processor id updated by the reserve */
	177	size_t slot_size; /* size of the reserved slot */
	178	unsigned long buf_offset; /* offset following the record header */
	179	unsigned long pre_offset; /*
	180	* Initial offset position _before_
	181	* the record is written. Positioned
	182	* prior to record header alignment
	183	* padding.
	184	*/
	185	u64 tsc; /* time-stamp counter value */
	186	unsigned int rflags; /* reservation flags */
	187
	188	struct lttng_kernel_ring_buffer buf; /
	189	* buffer corresponding to processor id
	190	* for this channel
	191	*/
	192	struct lttng_kernel_ring_buffer_backend_pages *backend_pages;
	193
	194	/*
	195	* Records lost counts are only loaded into these fields before
	196	* reserving the last bytes from the ring buffer.
	197	*/
	198	unsigned long records_lost_full;
	199	unsigned long records_lost_wrap;
	200	unsigned long records_lost_big;
	201	};
	202
	203	/*
	204	* ring buffer context
	205	*
	206	* Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
	207	* lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
	208	* lib_ring_buffer_write().
	209	*/
	210	struct lttng_kernel_ring_buffer_ctx {
	211	/* Private ring buffer context, set by reserve callback. */
	212	struct lttng_kernel_ring_buffer_ctx_private priv;
	213
	214	/* input received by lib_ring_buffer_reserve(), saved here. */
	215	void client_priv; / Ring buffer client private data */
	216
	217	size_t data_size; /* size of payload */
	218	int largest_align; /*
	219	* alignment of the largest element
	220	* in the payload
	221	*/
	222	struct lttng_kernel_probe_ctx probe_ctx; / Probe context */
	223	};
	224
	225	/**
	226	* lib_ring_buffer_ctx_init - initialize ring buffer context
	227	* @ctx: ring buffer context to initialize
	228	* @client_priv: client private data
	229	* @data_size: size of record data payload. It must be greater than 0.
	230	* @largest_align: largest alignment within data payload types
	231	*/
	232	static inline
	233	void lib_ring_buffer_ctx_init(struct lttng_kernel_ring_buffer_ctx *ctx,
	234	void *client_priv,
	235	size_t data_size, int largest_align,
	236	struct lttng_kernel_probe_ctx *probe_ctx)
	237	{
	238	ctx->client_priv = client_priv;
	239	ctx->data_size = data_size;
	240	ctx->largest_align = largest_align;
	241	ctx->probe_ctx = probe_ctx;
	242	}
	243
	244	/*
	245	* Reservation flags.
	246	*
	247	* RING_BUFFER_RFLAG_FULL_TSC
	248	*
	249	* This flag is passed to record_header_size() and to the primitive used to
	250	* write the record header. It indicates that the full 64-bit time value is
	251	* needed in the record header. If this flag is not set, the record header needs
	252	* only to contain "tsc_bits" bit of time value.
	253	*
	254	* Reservation flags can be added by the client, starting from
	255	* "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
	256	* record_header_size() to lib_ring_buffer_write_record_header().
	257	*/
	258	#define RING_BUFFER_RFLAG_FULL_TSC (1U << 0)
	259	#define RING_BUFFER_RFLAG_END (1U << 1)
	260
	261	#ifndef LTTNG_TRACER_CORE_H
	262	#error "lttng/tracer-core.h is needed for RING_BUFFER_ALIGN define"
	263	#endif
	264
	265	/*
	266	* We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
	267	* compile-time. We have to duplicate the "config->align" information and the
	268	* definition here because config->align is used both in the slow and fast
	269	* paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
	270	*/
	271	#ifdef RING_BUFFER_ALIGN
	272
	273	# define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */
	274
	275	/*
	276	* Calculate the offset needed to align the type.
	277	* size_of_type must be non-zero.
	278	*/
	279	static inline
	280	unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
	281	{
	282	return offset_align(align_drift, size_of_type);
	283	}
	284
	285	#else
	286
	287	# define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
	288
	289	/*
	290	* Calculate the offset needed to align the type.
	291	* size_of_type must be non-zero.
	292	*/
	293	static inline
	294	unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
	295	{
	296	return 0;
	297	}
	298
	299	#endif
	300
	301	/**
	302	* lib_ring_buffer_align_ctx - Align context offset on "alignment"
	303	* @ctx: ring buffer context.
	304	*/
	305	static inline
	306	void lib_ring_buffer_align_ctx(struct lttng_kernel_ring_buffer_ctx *ctx,
	307	size_t alignment)
	308	{
	309	ctx->priv.buf_offset += lib_ring_buffer_align(ctx->priv.buf_offset,
	310	alignment);
	311	}
	312
	313	/*
	314	* lib_ring_buffer_check_config() returns 0 on success.
	315	* Used internally to check for valid configurations at channel creation.
	316	*/
	317	static inline
	318	int lib_ring_buffer_check_config(const struct lttng_kernel_ring_buffer_config *config,
	319	unsigned int switch_timer_interval,
	320	unsigned int read_timer_interval)
	321	{
	322	if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
	323	&& config->sync == RING_BUFFER_SYNC_PER_CPU
	324	&& switch_timer_interval)
	325	return -EINVAL;
	326	return 0;
	327	}
	328
	329	#include <ringbuffer/vatomic.h>
	330
	331	#endif /* _LIB_RING_BUFFER_CONFIG_H */