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

/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
 *
 * ringbuffer/frontend_internal.h
 *
 * Ring Buffer Library Synchronization Header (internal helpers).
 *
 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * See ring_buffer_frontend.c for more information on wait-free algorithms.
 */

#ifndef _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
#define _LIB_RING_BUFFER_FRONTEND_INTERNAL_H

#include <ringbuffer/config.h>
#include <ringbuffer/backend_types.h>
#include <ringbuffer/frontend_types.h>
#include <lttng/prio_heap.h>	/* For per-CPU read-side iterator */

/* Buffer offset macros */

/* buf_trunc mask selects only the buffer number. */
static inline
unsigned long buf_trunc(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return offset & ~(chan->backend.buf_size - 1);

}

/* Select the buffer number value (counter). */
static inline
unsigned long buf_trunc_val(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return buf_trunc(offset, chan) >> chan->backend.buf_size_order;
}

/* buf_offset mask selects only the offset within the current buffer. */
static inline
unsigned long buf_offset(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return offset & (chan->backend.buf_size - 1);
}

/* subbuf_offset mask selects the offset within the current subbuffer. */
static inline
unsigned long subbuf_offset(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return offset & (chan->backend.subbuf_size - 1);
}

/* subbuf_trunc mask selects the subbuffer number. */
static inline
unsigned long subbuf_trunc(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return offset & ~(chan->backend.subbuf_size - 1);
}

/* subbuf_align aligns the offset to the next subbuffer. */
static inline
unsigned long subbuf_align(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return (offset + chan->backend.subbuf_size)
	       & ~(chan->backend.subbuf_size - 1);
}

/* subbuf_index returns the index of the current subbuffer within the buffer. */
static inline
unsigned long subbuf_index(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
{
	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
}

/*
 * Last timestamp comparison functions. Check if the current timestamp
 * overflows timestamp_bits bits from the last timestamp read. When
 * overflows are detected, the full 64-bit timestamp counter should be
 * written in the record header. Reads and writes last_timestamp
 * atomically.
 */

#if (BITS_PER_LONG == 32)
static inline
void save_last_timestamp(const struct lttng_kernel_ring_buffer_config *config,
		   struct lttng_kernel_ring_buffer *buf, u64 timestamp)
{
	if (config->timestamp_bits == 0 || config->timestamp_bits == 64)
		return;

	/*
	 * Ensure the compiler performs this update in a single instruction.
	 */
	v_set(config, &buf->last_timestamp, (unsigned long)(timestamp >> config->timestamp_bits));
}

static inline
int last_timestamp_overflow(const struct lttng_kernel_ring_buffer_config *config,
		      struct lttng_kernel_ring_buffer *buf, u64 timestamp)
{
	unsigned long timestamp_shifted;

	if (config->timestamp_bits == 0 || config->timestamp_bits == 64)
		return 0;

	timestamp_shifted = (unsigned long)(timestamp >> config->timestamp_bits);
	if (unlikely(timestamp_shifted
		     - (unsigned long)v_read(config, &buf->last_timestamp)))
		return 1;
	else
		return 0;
}
#else
static inline
void save_last_timestamp(const struct lttng_kernel_ring_buffer_config *config,
		   struct lttng_kernel_ring_buffer *buf, u64 timestamp)
{
	if (config->timestamp_bits == 0 || config->timestamp_bits == 64)
		return;

	v_set(config, &buf->last_timestamp, (unsigned long)timestamp);
}

static inline
int last_timestamp_overflow(const struct lttng_kernel_ring_buffer_config *config,
		      struct lttng_kernel_ring_buffer *buf, u64 timestamp)
{
	if (config->timestamp_bits == 0 || config->timestamp_bits == 64)
		return 0;

	if (unlikely((timestamp - v_read(config, &buf->last_timestamp))
		     >> config->timestamp_bits))
		return 1;
	else
		return 0;
}
#endif

extern
int lib_ring_buffer_reserve_slow(struct lttng_kernel_ring_buffer_ctx *ctx,
		void *client_ctx);

extern
void lib_ring_buffer_switch_slow(struct lttng_kernel_ring_buffer *buf,
				 enum switch_mode mode);

extern
void lib_ring_buffer_check_deliver_slow(const struct lttng_kernel_ring_buffer_config *config,
				   struct lttng_kernel_ring_buffer *buf,
			           struct lttng_kernel_ring_buffer_channel *chan,
			           unsigned long offset,
				   unsigned long commit_count,
			           unsigned long idx,
				   const struct lttng_kernel_ring_buffer_ctx *ctx);

extern
void lib_ring_buffer_switch_remote(struct lttng_kernel_ring_buffer *buf);
extern
void lib_ring_buffer_switch_remote_empty(struct lttng_kernel_ring_buffer *buf);
extern
void lib_ring_buffer_clear(struct lttng_kernel_ring_buffer *buf);

/* Buffer write helpers */

static inline
void lib_ring_buffer_reserve_push_reader(struct lttng_kernel_ring_buffer *buf,
					 struct lttng_kernel_ring_buffer_channel *chan,
					 unsigned long offset)
{
	unsigned long consumed_old, consumed_new;

	do {
		consumed_old = atomic_long_read(&buf->consumed);
		/*
		 * If buffer is in overwrite mode, push the reader consumed
		 * count if the write position has reached it and we are not
		 * at the first iteration (don't push the reader farther than
		 * the writer). This operation can be done concurrently by many
		 * writers in the same buffer, the writer being at the farthest
		 * write position sub-buffer index in the buffer being the one
		 * which will win this loop.
		 */
		if (unlikely(subbuf_trunc(offset, chan)
			      - subbuf_trunc(consumed_old, chan)
			     >= chan->backend.buf_size))
			consumed_new = subbuf_align(consumed_old, chan);
		else
			return;
	} while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
					      consumed_new) != consumed_old));
}

/*
 * Move consumed position to the beginning of subbuffer in which the
 * write offset is. Should only be used on ring buffers that are not
 * actively being written into, because clear_reader does not take into
 * account the commit counters when moving the consumed position, which
 * can make concurrent trace producers or consumers observe consumed
 * position further than the write offset, which breaks ring buffer
 * algorithm guarantees.
 */
static inline
void lib_ring_buffer_clear_reader(struct lttng_kernel_ring_buffer *buf,
				  struct lttng_kernel_ring_buffer_channel *chan)
{
	const struct lttng_kernel_ring_buffer_config *config = &chan->backend.config;
	unsigned long offset, consumed_old, consumed_new;

	do {
		offset = v_read(config, &buf->offset);
		consumed_old = atomic_long_read(&buf->consumed);
		CHAN_WARN_ON(chan, (long) (subbuf_trunc(offset, chan)
				- subbuf_trunc(consumed_old, chan))
				< 0);
		consumed_new = subbuf_trunc(offset, chan);
	} while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
					      consumed_new) != consumed_old));
}

static inline
int lib_ring_buffer_pending_data(const struct lttng_kernel_ring_buffer_config *config,
				 struct lttng_kernel_ring_buffer *buf,
				 struct lttng_kernel_ring_buffer_channel *chan)
{
	return !!subbuf_offset(v_read(config, &buf->offset), chan);
}

static inline
unsigned long lib_ring_buffer_get_data_size(const struct lttng_kernel_ring_buffer_config *config,
					    struct lttng_kernel_ring_buffer *buf,
					    unsigned long idx)
{
	return subbuffer_get_data_size(config, &buf->backend, idx);
}

/*
 * Check if all space reservation in a buffer have been committed. This helps
 * knowing if an execution context is nested (for per-cpu buffers only).
 * This is a very specific ftrace use-case, so we keep this as "internal" API.
 */
static inline
int lib_ring_buffer_reserve_committed(const struct lttng_kernel_ring_buffer_config *config,
				      struct lttng_kernel_ring_buffer *buf,
				      struct lttng_kernel_ring_buffer_channel *chan)
{
	unsigned long offset, idx, commit_count;

	CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
	CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);

	/*
	 * Read offset and commit count in a loop so they are both read
	 * atomically wrt interrupts. By deal with interrupt concurrency by
	 * restarting both reads if the offset has been pushed. Note that given
	 * we only have to deal with interrupt concurrency here, an interrupt
	 * modifying the commit count will also modify "offset", so it is safe
	 * to only check for offset modifications.
	 */
	do {
		offset = v_read(config, &buf->offset);
		idx = subbuf_index(offset, chan);
		commit_count = v_read(config, &buf->commit_hot[idx].cc);
	} while (offset != v_read(config, &buf->offset));

	return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
		     - (commit_count & chan->commit_count_mask) == 0);
}

/*
 * Receive end of subbuffer timestamp as parameter. It has been read in the
 * space reservation loop of either reserve or switch, which ensures it
 * progresses monotonically with event records in the buffer. Therefore,
 * it ensures that the end timestamp of a subbuffer is <= begin
 * timestamp of the following subbuffers.
 */
static inline
void lib_ring_buffer_check_deliver(const struct lttng_kernel_ring_buffer_config *config,
				   struct lttng_kernel_ring_buffer *buf,
			           struct lttng_kernel_ring_buffer_channel *chan,
			           unsigned long offset,
				   unsigned long commit_count,
			           unsigned long idx,
				   const struct lttng_kernel_ring_buffer_ctx *ctx)
{
	unsigned long old_commit_count = commit_count
					 - chan->backend.subbuf_size;

	/* Check if all commits have been done */
	if (unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
		     - (old_commit_count & chan->commit_count_mask) == 0))
		lib_ring_buffer_check_deliver_slow(config, buf, chan, offset,
			commit_count, idx, ctx);
}

/*
 * lib_ring_buffer_write_commit_counter
 *
 * For flight recording. must be called after commit.
 * This function increments the subbuffer's commit_seq counter each time the
 * commit count reaches back the reserve offset (modulo subbuffer size). It is
 * useful for crash dump.
 */
static inline
void lib_ring_buffer_write_commit_counter(const struct lttng_kernel_ring_buffer_config *config,
					  struct lttng_kernel_ring_buffer *buf,
				          struct lttng_kernel_ring_buffer_channel *chan,
				          unsigned long buf_offset,
				          unsigned long commit_count,
					  struct commit_counters_hot *cc_hot)
{
	unsigned long commit_seq_old;

	if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
		return;

	/*
	 * subbuf_offset includes commit_count_mask. We can simply
	 * compare the offsets within the subbuffer without caring about
	 * buffer full/empty mismatch because offset is never zero here
	 * (subbuffer header and record headers have non-zero length).
	 */
	if (unlikely(subbuf_offset(buf_offset - commit_count, chan)))
		return;

	commit_seq_old = v_read(config, &cc_hot->seq);
	if (likely((long) (commit_seq_old - commit_count) < 0))
		v_set(config, &cc_hot->seq, commit_count);
}

extern int lib_ring_buffer_create(struct lttng_kernel_ring_buffer *buf,
				  struct channel_backend *chanb, int cpu);
extern void lib_ring_buffer_free(struct lttng_kernel_ring_buffer *buf);

/* Keep track of trap nesting inside ring buffer code */
DECLARE_PER_CPU(unsigned int, lib_ring_buffer_nesting);

#endif /* _LIB_RING_BUFFER_FRONTEND_INTERNAL_H */
Commit	Line	Data
b7cdc182	1	/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
9f36eaed	2	*
24591303	3	* ringbuffer/frontend_internal.h
f3bc08c5	4	*
f3bc08c5 MD	5	* Ring Buffer Library Synchronization Header (internal helpers).
f3bc08c5 MD	6	*
886d51a3 MD	7	* Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
886d51a3 MD	8	*
f3bc08c5	9	* See ring_buffer_frontend.c for more information on wait-free algorithms.
f3bc08c5 MD	10	*/
f3bc08c5 MD	11
9f36eaed MJ	12	#ifndef _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
	13	#define _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
	14
24591303 MD	15	#include <ringbuffer/config.h>
	16	#include <ringbuffer/backend_types.h>
	17	#include <ringbuffer/frontend_types.h>
a071f25d	18	#include <lttng/prio_heap.h> /* For per-CPU read-side iterator */
f3bc08c5 MD	19
	20	/* Buffer offset macros */
	21
	22	/* buf_trunc mask selects only the buffer number. */
	23	static inline
860c213b	24	unsigned long buf_trunc(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	25	{
	26	return offset & ~(chan->backend.buf_size - 1);
	27
	28	}
	29
	30	/* Select the buffer number value (counter). */
	31	static inline
860c213b	32	unsigned long buf_trunc_val(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	33	{
	34	return buf_trunc(offset, chan) >> chan->backend.buf_size_order;
	35	}
	36
	37	/* buf_offset mask selects only the offset within the current buffer. */
	38	static inline
860c213b	39	unsigned long buf_offset(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	40	{
	41	return offset & (chan->backend.buf_size - 1);
	42	}
	43
	44	/* subbuf_offset mask selects the offset within the current subbuffer. */
	45	static inline
860c213b	46	unsigned long subbuf_offset(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	47	{
	48	return offset & (chan->backend.subbuf_size - 1);
	49	}
	50
	51	/* subbuf_trunc mask selects the subbuffer number. */
	52	static inline
860c213b	53	unsigned long subbuf_trunc(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	54	{
	55	return offset & ~(chan->backend.subbuf_size - 1);
	56	}
	57
	58	/* subbuf_align aligns the offset to the next subbuffer. */
	59	static inline
860c213b	60	unsigned long subbuf_align(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	61	{
	62	return (offset + chan->backend.subbuf_size)
	63	& ~(chan->backend.subbuf_size - 1);
	64	}
	65
	66	/* subbuf_index returns the index of the current subbuffer within the buffer. */
	67	static inline
860c213b	68	unsigned long subbuf_index(unsigned long offset, struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	69	{
	70	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
	71	}
	72
	73	/*
3a6d0934 MD	74	* Last timestamp comparison functions. Check if the current timestamp
	75	* overflows timestamp_bits bits from the last timestamp read. When
	76	* overflows are detected, the full 64-bit timestamp counter should be
	77	* written in the record header. Reads and writes last_timestamp
	78	* atomically.
f3bc08c5 MD	79	*/
	80
	81	#if (BITS_PER_LONG == 32)
	82	static inline
3a6d0934 MD	83	void save_last_timestamp(const struct lttng_kernel_ring_buffer_config *config,
3a6d0934 MD	84	struct lttng_kernel_ring_buffer *buf, u64 timestamp)
f3bc08c5	85	{
3a6d0934	86	if (config->timestamp_bits == 0 \|\| config->timestamp_bits == 64)
f3bc08c5 MD	87	return;
	88
	89	/*
	90	* Ensure the compiler performs this update in a single instruction.
	91	*/
3a6d0934	92	v_set(config, &buf->last_timestamp, (unsigned long)(timestamp >> config->timestamp_bits));
f3bc08c5 MD	93	}
	94
	95	static inline
3a6d0934 MD	96	int last_timestamp_overflow(const struct lttng_kernel_ring_buffer_config *config,
3a6d0934 MD	97	struct lttng_kernel_ring_buffer *buf, u64 timestamp)
f3bc08c5	98	{
3a6d0934	99	unsigned long timestamp_shifted;
f3bc08c5	100
3a6d0934	101	if (config->timestamp_bits == 0 \|\| config->timestamp_bits == 64)
f3bc08c5 MD	102	return 0;
f3bc08c5 MD	103
3a6d0934 MD	104	timestamp_shifted = (unsigned long)(timestamp >> config->timestamp_bits);
	105	if (unlikely(timestamp_shifted
	106	- (unsigned long)v_read(config, &buf->last_timestamp)))
f3bc08c5 MD	107	return 1;
	108	else
	109	return 0;
	110	}
	111	#else
	112	static inline
3a6d0934 MD	113	void save_last_timestamp(const struct lttng_kernel_ring_buffer_config *config,
3a6d0934 MD	114	struct lttng_kernel_ring_buffer *buf, u64 timestamp)
f3bc08c5	115	{
3a6d0934	116	if (config->timestamp_bits == 0 \|\| config->timestamp_bits == 64)
f3bc08c5 MD	117	return;
f3bc08c5 MD	118
3a6d0934	119	v_set(config, &buf->last_timestamp, (unsigned long)timestamp);
f3bc08c5 MD	120	}
	121
	122	static inline
3a6d0934 MD	123	int last_timestamp_overflow(const struct lttng_kernel_ring_buffer_config *config,
3a6d0934 MD	124	struct lttng_kernel_ring_buffer *buf, u64 timestamp)
f3bc08c5	125	{
3a6d0934	126	if (config->timestamp_bits == 0 \|\| config->timestamp_bits == 64)
f3bc08c5 MD	127	return 0;
f3bc08c5 MD	128
3a6d0934 MD	129	if (unlikely((timestamp - v_read(config, &buf->last_timestamp))
3a6d0934 MD	130	>> config->timestamp_bits))
f3bc08c5 MD	131	return 1;
	132	else
	133	return 0;
	134	}
	135	#endif
	136
	137	extern
8a57ec02	138	int lib_ring_buffer_reserve_slow(struct lttng_kernel_ring_buffer_ctx *ctx,
cc62f29e	139	void *client_ctx);
f3bc08c5 MD	140
f3bc08c5 MD	141	extern
e20c0fec	142	void lib_ring_buffer_switch_slow(struct lttng_kernel_ring_buffer *buf,
f3bc08c5 MD	143	enum switch_mode mode);
f3bc08c5 MD	144
aece661f	145	extern
e20c0fec MD	146	void lib_ring_buffer_check_deliver_slow(const struct lttng_kernel_ring_buffer_config *config,
e20c0fec MD	147	struct lttng_kernel_ring_buffer *buf,
860c213b	148	struct lttng_kernel_ring_buffer_channel *chan,
aece661f MD	149	unsigned long offset,
	150	unsigned long commit_count,
	151	unsigned long idx,
b2cf5e0b	152	const struct lttng_kernel_ring_buffer_ctx *ctx);
aece661f	153
5e391252	154	extern
e20c0fec	155	void lib_ring_buffer_switch_remote(struct lttng_kernel_ring_buffer *buf);
c6f05468	156	extern
e20c0fec	157	void lib_ring_buffer_switch_remote_empty(struct lttng_kernel_ring_buffer *buf);
c245d0d3	158	extern
e20c0fec	159	void lib_ring_buffer_clear(struct lttng_kernel_ring_buffer *buf);
5e391252	160
f3bc08c5 MD	161	/* Buffer write helpers */
	162
	163	static inline
e20c0fec	164	void lib_ring_buffer_reserve_push_reader(struct lttng_kernel_ring_buffer *buf,
860c213b	165	struct lttng_kernel_ring_buffer_channel *chan,
f3bc08c5 MD	166	unsigned long offset)
	167	{
	168	unsigned long consumed_old, consumed_new;
	169
	170	do {
	171	consumed_old = atomic_long_read(&buf->consumed);
	172	/*
	173	* If buffer is in overwrite mode, push the reader consumed
	174	* count if the write position has reached it and we are not
	175	* at the first iteration (don't push the reader farther than
	176	* the writer). This operation can be done concurrently by many
	177	* writers in the same buffer, the writer being at the farthest
	178	* write position sub-buffer index in the buffer being the one
	179	* which will win this loop.
	180	*/
	181	if (unlikely(subbuf_trunc(offset, chan)
	182	- subbuf_trunc(consumed_old, chan)
	183	>= chan->backend.buf_size))
	184	consumed_new = subbuf_align(consumed_old, chan);
	185	else
	186	return;
	187	} while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
	188	consumed_new) != consumed_old));
	189	}
	190
c245d0d3 MD	191	/*
c245d0d3 MD	192	* Move consumed position to the beginning of subbuffer in which the
ac4a87e5 MD	193	* write offset is. Should only be used on ring buffers that are not
	194	* actively being written into, because clear_reader does not take into
	195	* account the commit counters when moving the consumed position, which
	196	* can make concurrent trace producers or consumers observe consumed
	197	* position further than the write offset, which breaks ring buffer
	198	* algorithm guarantees.
c245d0d3 MD	199	*/
c245d0d3 MD	200	static inline
e20c0fec	201	void lib_ring_buffer_clear_reader(struct lttng_kernel_ring_buffer *buf,
860c213b	202	struct lttng_kernel_ring_buffer_channel *chan)
c245d0d3	203	{
e20c0fec	204	const struct lttng_kernel_ring_buffer_config *config = &chan->backend.config;
c245d0d3 MD	205	unsigned long offset, consumed_old, consumed_new;
	206
	207	do {
	208	offset = v_read(config, &buf->offset);
	209	consumed_old = atomic_long_read(&buf->consumed);
ac4a87e5 MD	210	CHAN_WARN_ON(chan, (long) (subbuf_trunc(offset, chan)
	211	- subbuf_trunc(consumed_old, chan))
	212	< 0);
	213	consumed_new = subbuf_trunc(offset, chan);
c245d0d3 MD	214	} while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
	215	consumed_new) != consumed_old));
	216	}
	217
f3bc08c5	218	static inline
e20c0fec MD	219	int lib_ring_buffer_pending_data(const struct lttng_kernel_ring_buffer_config *config,
e20c0fec MD	220	struct lttng_kernel_ring_buffer *buf,
860c213b	221	struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	222	{
	223	return !!subbuf_offset(v_read(config, &buf->offset), chan);
	224	}
	225
	226	static inline
e20c0fec MD	227	unsigned long lib_ring_buffer_get_data_size(const struct lttng_kernel_ring_buffer_config *config,
e20c0fec MD	228	struct lttng_kernel_ring_buffer *buf,
f3bc08c5 MD	229	unsigned long idx)
	230	{
	231	return subbuffer_get_data_size(config, &buf->backend, idx);
	232	}
	233
	234	/*
	235	* Check if all space reservation in a buffer have been committed. This helps
	236	* knowing if an execution context is nested (for per-cpu buffers only).
	237	* This is a very specific ftrace use-case, so we keep this as "internal" API.
	238	*/
	239	static inline
e20c0fec MD	240	int lib_ring_buffer_reserve_committed(const struct lttng_kernel_ring_buffer_config *config,
e20c0fec MD	241	struct lttng_kernel_ring_buffer *buf,
860c213b	242	struct lttng_kernel_ring_buffer_channel *chan)
f3bc08c5 MD	243	{
	244	unsigned long offset, idx, commit_count;
	245
	246	CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
	247	CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);
	248
	249	/*
	250	* Read offset and commit count in a loop so they are both read
	251	* atomically wrt interrupts. By deal with interrupt concurrency by
	252	* restarting both reads if the offset has been pushed. Note that given
	253	* we only have to deal with interrupt concurrency here, an interrupt
	254	* modifying the commit count will also modify "offset", so it is safe
	255	* to only check for offset modifications.
	256	*/
	257	do {
	258	offset = v_read(config, &buf->offset);
	259	idx = subbuf_index(offset, chan);
	260	commit_count = v_read(config, &buf->commit_hot[idx].cc);
	261	} while (offset != v_read(config, &buf->offset));
	262
	263	return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
	264	- (commit_count & chan->commit_count_mask) == 0);
	265	}
	266
635e457c	267	/*
3a6d0934	268	* Receive end of subbuffer timestamp as parameter. It has been read in the
635e457c MD	269	* space reservation loop of either reserve or switch, which ensures it
	270	* progresses monotonically with event records in the buffer. Therefore,
	271	* it ensures that the end timestamp of a subbuffer is <= begin
	272	* timestamp of the following subbuffers.
	273	*/
f3bc08c5	274	static inline
e20c0fec MD	275	void lib_ring_buffer_check_deliver(const struct lttng_kernel_ring_buffer_config *config,
e20c0fec MD	276	struct lttng_kernel_ring_buffer *buf,
860c213b	277	struct lttng_kernel_ring_buffer_channel *chan,
f3bc08c5 MD	278	unsigned long offset,
f3bc08c5 MD	279	unsigned long commit_count,
635e457c	280	unsigned long idx,
b2cf5e0b	281	const struct lttng_kernel_ring_buffer_ctx *ctx)
f3bc08c5 MD	282	{
	283	unsigned long old_commit_count = commit_count
	284	- chan->backend.subbuf_size;
f3bc08c5 MD	285
	286	/* Check if all commits have been done */
	287	if (unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
aece661f MD	288	- (old_commit_count & chan->commit_count_mask) == 0))
aece661f MD	289	lib_ring_buffer_check_deliver_slow(config, buf, chan, offset,
b2cf5e0b	290	commit_count, idx, ctx);
f3bc08c5 MD	291	}
	292
	293	/*
	294	* lib_ring_buffer_write_commit_counter
	295	*
	296	* For flight recording. must be called after commit.
	297	* This function increments the subbuffer's commit_seq counter each time the
	298	* commit count reaches back the reserve offset (modulo subbuffer size). It is
	299	* useful for crash dump.
	300	*/
	301	static inline
e20c0fec MD	302	void lib_ring_buffer_write_commit_counter(const struct lttng_kernel_ring_buffer_config *config,
e20c0fec MD	303	struct lttng_kernel_ring_buffer *buf,
860c213b	304	struct lttng_kernel_ring_buffer_channel *chan,
f3bc08c5	305	unsigned long buf_offset,
8ec496cf MD	306	unsigned long commit_count,
8ec496cf MD	307	struct commit_counters_hot *cc_hot)
f3bc08c5	308	{
7915e163	309	unsigned long commit_seq_old;
f3bc08c5 MD	310
	311	if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
	312	return;
	313
f3bc08c5 MD	314	/*
	315	* subbuf_offset includes commit_count_mask. We can simply
	316	* compare the offsets within the subbuffer without caring about
	317	* buffer full/empty mismatch because offset is never zero here
	318	* (subbuffer header and record headers have non-zero length).
	319	*/
7915e163	320	if (unlikely(subbuf_offset(buf_offset - commit_count, chan)))
f3bc08c5 MD	321	return;
f3bc08c5 MD	322
8ec496cf	323	commit_seq_old = v_read(config, &cc_hot->seq);
6212b6b6	324	if (likely((long) (commit_seq_old - commit_count) < 0))
8ec496cf	325	v_set(config, &cc_hot->seq, commit_count);
f3bc08c5 MD	326	}
f3bc08c5 MD	327
e20c0fec	328	extern int lib_ring_buffer_create(struct lttng_kernel_ring_buffer *buf,
f3bc08c5	329	struct channel_backend *chanb, int cpu);
e20c0fec	330	extern void lib_ring_buffer_free(struct lttng_kernel_ring_buffer *buf);
f3bc08c5 MD	331
	332	/* Keep track of trap nesting inside ring buffer code */
	333	DECLARE_PER_CPU(unsigned int, lib_ring_buffer_nesting);
	334
886d51a3	335	#endif /* _LIB_RING_BUFFER_FRONTEND_INTERNAL_H */