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

#ifndef _LINUX_RING_BUFFER_CONFIG_H
#define _LINUX_RING_BUFFER_CONFIG_H

/*
 * linux/ringbuffer/config.h
 *
 * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Ring buffer configuration header. Note: after declaring the standard inline
 * functions, clients should also include linux/ringbuffer/api.h.
 *
 * Dual LGPL v2.1/GPL v2 license.
 */

#include <errno.h>
#include "lttng/ust-tracer.h"
#include "lttng/usterr-signal-safe.h"
#include "lttng/kcompat/kcompat.h"
#include "lttng/align.h"

struct lttng_ust_lib_ring_buffer;
struct channel;
struct lttng_ust_lib_ring_buffer_config;
struct lttng_ust_lib_ring_buffer_ctx;
struct lttng_ust_shm_handle *handle;

/*
 * 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_ust_lib_ring_buffer_client_cb {
	/* Mandatory callbacks */

	/* A static inline version is also required for fast path */
	u64 (*ring_buffer_clock_read) (struct channel *chan);
	size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
				      struct channel *chan, size_t offset,
				      size_t *pre_header_padding,
				      struct lttng_ust_lib_ring_buffer_ctx *ctx);

	/* Slow path only, at subbuffer switch */
	size_t (*subbuffer_header_size) (void);
	void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, u64 tsc,
			      unsigned int subbuf_idx,
			      struct lttng_ust_shm_handle *handle);
	void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, u64 tsc,
			    unsigned int subbuf_idx, unsigned long data_size,
			    struct lttng_ust_shm_handle *handle);

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

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

	/*
	 * 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_ust_lib_ring_buffer_config *config,
			    struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
			    size_t offset, size_t *header_len,
			    size_t *payload_len, u64 *timestamp,
			    struct lttng_ust_shm_handle *handle);
};

/*
 * 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 deferrable 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.
 *
 * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 * has the responsibility to perform wakeups.
 */
struct lttng_ust_lib_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,
						 * not lock-free
						 * (takes spinlock).
						 */
	} wakeup;
	/*
	 * tsc_bits: timestamp bits saved at each record.
	 *   0 and 64 disable the timestamp compression scheme.
	 */
	unsigned int tsc_bits;
	struct lttng_ust_lib_ring_buffer_client_cb cb;
	/*
	 * client_type is used by the consumer process (which is in a
	 * different address space) to lookup the appropriate client
	 * callbacks and update the cb pointers.
	 */
	int client_type;
};

/*
 * 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_ust_lib_ring_buffer_ctx {
	/* input received by lib_ring_buffer_reserve(), saved here. */
	struct channel *chan;		/* channel */
	void *priv;			/* client private data */
	struct lttng_ust_shm_handle *handle;	/* shared-memory handle */
	size_t data_size;		/* size of payload */
	int largest_align;		/*
					 * alignment of the largest element
					 * in the payload
					 */
	int cpu;			/* processor id */

	/* output from lib_ring_buffer_reserve() */
	struct lttng_ust_lib_ring_buffer *buf;	/*
					 * buffer corresponding to processor id
					 * for this channel
					 */
	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 */
};

/**
 * lib_ring_buffer_ctx_init - initialize ring buffer context
 * @ctx: ring buffer context to initialize
 * @chan: channel
 * @priv: client private data
 * @data_size: size of record data payload
 * @largest_align: largest alignment within data payload types
 * @cpu: processor id
 */
static inline
void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
			      struct channel *chan, void *priv,
			      size_t data_size, int largest_align,
			      int cpu, struct lttng_ust_shm_handle *handle)
{
	ctx->chan = chan;
	ctx->priv = priv;
	ctx->data_size = data_size;
	ctx->largest_align = largest_align;
	ctx->cpu = cpu;
	ctx->rflags = 0;
	ctx->handle = handle;
}

/*
 * 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)

/*
 * 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_ust_lib_ring_buffer_ctx *ctx,
			   size_t alignment)
{
	ctx->buf_offset += lib_ring_buffer_align(ctx->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_ust_lib_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 <lttng/vatomic.h>

#endif /* _LINUX_RING_BUFFER_CONFIG_H */
Commit	Line	Data
a6352fd4 MD	1	#ifndef _LINUX_RING_BUFFER_CONFIG_H
	2	#define _LINUX_RING_BUFFER_CONFIG_H
	3
	4	/*
	5	* linux/ringbuffer/config.h
	6	*
	7	* Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	8	*
	9	* Ring buffer configuration header. Note: after declaring the standard inline
	10	* functions, clients should also include linux/ringbuffer/api.h.
	11	*
	12	* Dual LGPL v2.1/GPL v2 license.
	13	*/
	14
	15	#include <errno.h>
4318ae1b MD	16	#include "lttng/ust-tracer.h"
	17	#include "lttng/usterr-signal-safe.h"
	18	#include "lttng/kcompat/kcompat.h"
	19	#include "lttng/align.h"
a6352fd4	20
4cfec15c	21	struct lttng_ust_lib_ring_buffer;
a6352fd4	22	struct channel;
4cfec15c MD	23	struct lttng_ust_lib_ring_buffer_config;
4cfec15c MD	24	struct lttng_ust_lib_ring_buffer_ctx;
38fae1d3	25	struct lttng_ust_shm_handle *handle;
a6352fd4 MD	26
	27	/*
	28	* Ring buffer client callbacks. Only used by slow path, never on fast path.
	29	* For the fast path, record_header_size(), ring_buffer_clock_read() should be
	30	* provided as inline functions too. These may simply return 0 if not used by
	31	* the client.
	32	*/
4cfec15c	33	struct lttng_ust_lib_ring_buffer_client_cb {
a6352fd4 MD	34	/* Mandatory callbacks */
	35
	36	/* A static inline version is also required for fast path */
	37	u64 (ring_buffer_clock_read) (struct channel chan);
4cfec15c	38	size_t (record_header_size) (const struct lttng_ust_lib_ring_buffer_config config,
a6352fd4 MD	39	struct channel *chan, size_t offset,
a6352fd4 MD	40	size_t *pre_header_padding,
4cfec15c	41	struct lttng_ust_lib_ring_buffer_ctx *ctx);
a6352fd4 MD	42
	43	/* Slow path only, at subbuffer switch */
	44	size_t (*subbuffer_header_size) (void);
4cfec15c	45	void (buffer_begin) (struct lttng_ust_lib_ring_buffer buf, u64 tsc,
1d498196	46	unsigned int subbuf_idx,
38fae1d3	47	struct lttng_ust_shm_handle *handle);
4cfec15c	48	void (buffer_end) (struct lttng_ust_lib_ring_buffer buf, u64 tsc,
1d498196	49	unsigned int subbuf_idx, unsigned long data_size,
38fae1d3	50	struct lttng_ust_shm_handle *handle);
a6352fd4 MD	51
	52	/* Optional callbacks (can be set to NULL) */
	53
	54	/* Called at buffer creation/finalize */
4cfec15c	55	int (buffer_create) (struct lttng_ust_lib_ring_buffer buf, void *priv,
1d498196	56	int cpu, const char *name,
38fae1d3	57	struct lttng_ust_shm_handle *handle);
a6352fd4 MD	58	/*
	59	* Clients should guarantee that no new reader handle can be opened
	60	* after finalize.
	61	*/
4cfec15c	62	void (buffer_finalize) (struct lttng_ust_lib_ring_buffer buf,
1d498196	63	void *priv, int cpu,
38fae1d3	64	struct lttng_ust_shm_handle *handle);
a6352fd4 MD	65
	66	/*
	67	* Extract header length, payload length and timestamp from event
	68	* record. Used by buffer iterators. Timestamp is only used by channel
	69	* iterator.
	70	*/
4cfec15c MD	71	void (record_get) (const struct lttng_ust_lib_ring_buffer_config config,
4cfec15c MD	72	struct channel chan, struct lttng_ust_lib_ring_buffer buf,
a6352fd4	73	size_t offset, size_t *header_len,
1d498196	74	size_t payload_len, u64 timestamp,
38fae1d3	75	struct lttng_ust_shm_handle *handle);
a6352fd4 MD	76	};
	77
	78	/*
	79	* Ring buffer instance configuration.
	80	*
	81	* Declare as "static const" within the client object to ensure the inline fast
	82	* paths can be optimized.
	83	*
	84	* alloc/sync pairs:
	85	*
	86	* RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
	87	* Per-cpu buffers with per-cpu synchronization. Tracing must be performed
	88	* with preemption disabled (lib_ring_buffer_get_cpu() and
	89	* lib_ring_buffer_put_cpu()).
	90	*
	91	* RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
	92	* Per-cpu buffer with global synchronization. Tracing can be performed with
	93	* preemption enabled, statistically stays on the local buffers.
	94	*
	95	* RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
	96	* Should only be used for buffers belonging to a single thread or protected
	97	* by mutual exclusion by the client. Note that periodical sub-buffer switch
	98	* should be disabled in this kind of configuration.
	99	*
	100	* RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
	101	* Global shared buffer with global synchronization.
	102	*
	103	* wakeup:
	104	*
	105	* RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
	106	* buffers and wake up readers if data is ready. Mainly useful for tracers which
	107	* don't want to call into the wakeup code on the tracing path. Use in
	108	* combination with "read_timer_interval" channel_create() argument.
	109	*
	110	* RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
	111	* ready to read. Lower latencies before the reader is woken up. Mainly suitable
	112	* for drivers.
	113	*
	114	* RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
	115	* has the responsibility to perform wakeups.
	116	*/
4cfec15c	117	struct lttng_ust_lib_ring_buffer_config {
a6352fd4 MD	118	enum {
	119	RING_BUFFER_ALLOC_PER_CPU,
	120	RING_BUFFER_ALLOC_GLOBAL,
	121	} alloc;
	122	enum {
	123	RING_BUFFER_SYNC_PER_CPU, /* Wait-free */
	124	RING_BUFFER_SYNC_GLOBAL, /* Lock-free */
	125	} sync;
	126	enum {
	127	RING_BUFFER_OVERWRITE, /* Overwrite when buffer full */
	128	RING_BUFFER_DISCARD, /* Discard when buffer full */
	129	} mode;
	130	enum {
	131	RING_BUFFER_SPLICE,
	132	RING_BUFFER_MMAP,
	133	RING_BUFFER_READ, /* TODO */
	134	RING_BUFFER_ITERATOR,
	135	RING_BUFFER_NONE,
	136	} output;
	137	enum {
	138	RING_BUFFER_PAGE,
	139	RING_BUFFER_VMAP, /* TODO */
	140	RING_BUFFER_STATIC, /* TODO */
	141	} backend;
	142	enum {
	143	RING_BUFFER_NO_OOPS_CONSISTENCY,
	144	RING_BUFFER_OOPS_CONSISTENCY,
	145	} oops;
	146	enum {
	147	RING_BUFFER_IPI_BARRIER,
	148	RING_BUFFER_NO_IPI_BARRIER,
	149	} ipi;
	150	enum {
	151	RING_BUFFER_WAKEUP_BY_TIMER, /* wake up performed by timer */
	152	RING_BUFFER_WAKEUP_BY_WRITER, /*
	153	* writer wakes up reader,
	154	* not lock-free
	155	* (takes spinlock).
	156	*/
	157	} wakeup;
	158	/*
	159	* tsc_bits: timestamp bits saved at each record.
	160	* 0 and 64 disable the timestamp compression scheme.
	161	*/
	162	unsigned int tsc_bits;
4cfec15c	163	struct lttng_ust_lib_ring_buffer_client_cb cb;
c1fca457 MD	164	/*
	165	* client_type is used by the consumer process (which is in a
	166	* different address space) to lookup the appropriate client
	167	* callbacks and update the cb pointers.
	168	*/
	169	int client_type;
a6352fd4 MD	170	};
	171
	172	/*
	173	* ring buffer context
	174	*
	175	* Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
	176	* lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
	177	* lib_ring_buffer_write().
	178	*/
4cfec15c	179	struct lttng_ust_lib_ring_buffer_ctx {
a6352fd4 MD	180	/* input received by lib_ring_buffer_reserve(), saved here. */
	181	struct channel chan; / channel */
	182	void priv; / client private data */
38fae1d3	183	struct lttng_ust_shm_handle handle; / shared-memory handle */
a6352fd4 MD	184	size_t data_size; /* size of payload */
	185	int largest_align; /*
	186	* alignment of the largest element
	187	* in the payload
	188	*/
	189	int cpu; /* processor id */
	190
	191	/* output from lib_ring_buffer_reserve() */
4cfec15c	192	struct lttng_ust_lib_ring_buffer buf; /
a6352fd4 MD	193	* buffer corresponding to processor id
	194	* for this channel
	195	*/
	196	size_t slot_size; /* size of the reserved slot */
	197	unsigned long buf_offset; /* offset following the record header */
	198	unsigned long pre_offset; /*
	199	* Initial offset position _before_
	200	* the record is written. Positioned
	201	* prior to record header alignment
	202	* padding.
	203	*/
	204	u64 tsc; /* time-stamp counter value */
	205	unsigned int rflags; /* reservation flags */
	206	};
	207
	208	/**
	209	* lib_ring_buffer_ctx_init - initialize ring buffer context
	210	* @ctx: ring buffer context to initialize
	211	* @chan: channel
	212	* @priv: client private data
	213	* @data_size: size of record data payload
	214	* @largest_align: largest alignment within data payload types
	215	* @cpu: processor id
	216	*/
	217	static inline
4cfec15c	218	void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
a6352fd4 MD	219	struct channel chan, void priv,
a6352fd4 MD	220	size_t data_size, int largest_align,
38fae1d3	221	int cpu, struct lttng_ust_shm_handle *handle)
a6352fd4 MD	222	{
	223	ctx->chan = chan;
	224	ctx->priv = priv;
	225	ctx->data_size = data_size;
	226	ctx->largest_align = largest_align;
	227	ctx->cpu = cpu;
	228	ctx->rflags = 0;
1d498196	229	ctx->handle = handle;
a6352fd4 MD	230	}
	231
	232	/*
	233	* Reservation flags.
	234	*
	235	* RING_BUFFER_RFLAG_FULL_TSC
	236	*
	237	* This flag is passed to record_header_size() and to the primitive used to
	238	* write the record header. It indicates that the full 64-bit time value is
	239	* needed in the record header. If this flag is not set, the record header needs
	240	* only to contain "tsc_bits" bit of time value.
	241	*
	242	* Reservation flags can be added by the client, starting from
	243	* "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
	244	* record_header_size() to lib_ring_buffer_write_record_header().
	245	*/
	246	#define RING_BUFFER_RFLAG_FULL_TSC (1U << 0)
	247	#define RING_BUFFER_RFLAG_END (1U << 1)
	248
	249	/*
	250	* We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
	251	* compile-time. We have to duplicate the "config->align" information and the
	252	* definition here because config->align is used both in the slow and fast
	253	* paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
	254	*/
	255	#ifdef RING_BUFFER_ALIGN
	256
	257	# define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */
	258
	259	/*
	260	* Calculate the offset needed to align the type.
	261	* size_of_type must be non-zero.
	262	*/
	263	static inline
	264	unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
	265	{
	266	return offset_align(align_drift, size_of_type);
	267	}
	268
	269	#else
	270
	271	# define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
	272
	273	/*
	274	* Calculate the offset needed to align the type.
	275	* size_of_type must be non-zero.
	276	*/
	277	static inline
	278	unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
	279	{
	280	return 0;
	281	}
	282
	283	#endif
	284
	285	/**
	286	* lib_ring_buffer_align_ctx - Align context offset on "alignment"
	287	* @ctx: ring buffer context.
	288	*/
	289	static inline
4cfec15c	290	void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
a6352fd4 MD	291	size_t alignment)
	292	{
	293	ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
	294	alignment);
	295	}
	296
	297	/*
	298	* lib_ring_buffer_check_config() returns 0 on success.
	299	* Used internally to check for valid configurations at channel creation.
	300	*/
	301	static inline
4cfec15c	302	int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
a6352fd4 MD	303	unsigned int switch_timer_interval,
	304	unsigned int read_timer_interval)
	305	{
	306	if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
	307	&& config->sync == RING_BUFFER_SYNC_PER_CPU
	308	&& switch_timer_interval)
	309	return -EINVAL;
	310	return 0;
	311	}
	312
4318ae1b	313	#include <lttng/vatomic.h>
a6352fd4 MD	314
a6352fd4 MD	315	#endif /* _LINUX_RING_BUFFER_CONFIG_H */