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

#ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H
#define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H

/*
 * libringbuffer/frontend_internal.h
 *
 * Ring Buffer Library Synchronization Header (internal helpers).
 *
 * Copyright (C) 2005-2012 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
 *
 *
 * Author:
 *	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * See ring_buffer_frontend.c for more information on wait-free algorithms.
 *
 * Dual LGPL v2.1/GPL v2 license.
 */

#include <urcu/compiler.h>
#include <urcu/tls-compat.h>
#include <signal.h>
#include <stdint.h>
#include <pthread.h>

#include <lttng/ringbuffer-config.h>
#include "backend_types.h"
#include "frontend_types.h"
#include "shm.h"

/* Buffer offset macros */

/* buf_trunc mask selects only the buffer number. */
static inline
unsigned long buf_trunc(unsigned long offset, struct 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 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 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 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 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 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 channel *chan)
{
	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
}

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

#if (CAA_BITS_PER_LONG == 32)
static inline
void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
		   struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
{
	if (config->tsc_bits == 0 || config->tsc_bits == 64)
		return;

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

static inline
int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
		      struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
{
	unsigned long tsc_shifted;

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

	tsc_shifted = (unsigned long)(tsc >> config->tsc_bits);
	if (caa_unlikely(tsc_shifted
		     - (unsigned long)v_read(config, &buf->last_tsc)))
		return 1;
	else
		return 0;
}
#else
static inline
void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
		   struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
{
	if (config->tsc_bits == 0 || config->tsc_bits == 64)
		return;

	v_set(config, &buf->last_tsc, (unsigned long)tsc);
}

static inline
int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
		      struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
{
	if (config->tsc_bits == 0 || config->tsc_bits == 64)
		return 0;

	if (caa_unlikely((tsc - v_read(config, &buf->last_tsc))
		     >> config->tsc_bits))
		return 1;
	else
		return 0;
}
#endif

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

extern
void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf,
				 enum switch_mode mode,
				 struct lttng_ust_shm_handle *handle);

void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config,
				   struct lttng_ust_lib_ring_buffer *buf,
			           struct channel *chan,
			           unsigned long offset,
				   unsigned long commit_count,
			           unsigned long idx,
				   struct lttng_ust_shm_handle *handle,
				   uint64_t tsc);

/* Buffer write helpers */

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

	do {
		consumed_old = uatomic_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 (caa_unlikely(subbuf_trunc(offset, chan)
			      - subbuf_trunc(consumed_old, chan)
			     >= chan->backend.buf_size))
			consumed_new = subbuf_align(consumed_old, chan);
		else
			return;
	} while (caa_unlikely(uatomic_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_ust_lib_ring_buffer *buf,
				  struct lttng_ust_shm_handle *handle)
{
	struct channel *chan;
	const struct lttng_ust_lib_ring_buffer_config *config;
	unsigned long offset, consumed_old, consumed_new;

	chan = shmp(handle, buf->backend.chan);
	if (!chan)
		return;
	config = &chan->backend.config;

	do {
		offset = v_read(config, &buf->offset);
		consumed_old = uatomic_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 (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
					      consumed_new) != consumed_old));
}

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

static inline
unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config,
					    struct lttng_ust_lib_ring_buffer *buf,
					    unsigned long idx,
					    struct lttng_ust_shm_handle *handle)
{
	return subbuffer_get_data_size(config, &buf->backend, idx, handle);
}

/*
 * 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_ust_lib_ring_buffer_config *config,
				      struct lttng_ust_lib_ring_buffer *buf,
				      struct channel *chan,
				      struct lttng_ust_shm_handle *handle)
{
	unsigned long offset, idx, commit_count;
	struct commit_counters_hot *cc_hot;

	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);
		cc_hot = shmp_index(handle, buf->commit_hot, idx);
		if (caa_unlikely(!cc_hot))
			return 0;
		commit_count = v_read(config, &cc_hot->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 TSC 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_ust_lib_ring_buffer_config *config,
				   struct lttng_ust_lib_ring_buffer *buf,
			           struct channel *chan,
			           unsigned long offset,
				   unsigned long commit_count,
			           unsigned long idx,
				   struct lttng_ust_shm_handle *handle,
				   uint64_t tsc)
{
	unsigned long old_commit_count = commit_count
					 - chan->backend.subbuf_size;

	/* Check if all commits have been done */
	if (caa_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, handle, tsc);
}

/*
 * 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_ust_lib_ring_buffer_config *config,
					  struct lttng_ust_lib_ring_buffer *buf,
				          struct channel *chan,
				          unsigned long buf_offset,
				          unsigned long commit_count,
					  struct lttng_ust_shm_handle *handle,
					  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 (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan)))
		return;

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

extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf,
				  struct channel_backend *chanb, int cpu,
				  struct lttng_ust_shm_handle *handle,
				  struct shm_object *shmobj);
extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf,
				 struct lttng_ust_shm_handle *handle);

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

#endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */
Commit	Line	Data
e92f3e28 MD	1	#ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H
e92f3e28 MD	2	#define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H
852c2936 MD	3
852c2936 MD	4	/*
e92f3e28	5	* libringbuffer/frontend_internal.h
852c2936 MD	6	*
	7	* Ring Buffer Library Synchronization Header (internal helpers).
	8	*
e92f3e28 MD	9	* Copyright (C) 2005-2012 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
	24	*
	25	*
852c2936 MD	26	* Author:
	27	* Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	28	*
	29	* See ring_buffer_frontend.c for more information on wait-free algorithms.
	30	*
	31	* Dual LGPL v2.1/GPL v2 license.
	32	*/
	33
14641deb	34	#include <urcu/compiler.h>
8c90a710	35	#include <urcu/tls-compat.h>
2c44f5b9	36	#include <signal.h>
fb31eb73	37	#include <stdint.h>
2c44f5b9	38	#include <pthread.h>
14641deb	39
4318ae1b	40	#include <lttng/ringbuffer-config.h>
4931a13e MD	41	#include "backend_types.h"
4931a13e MD	42	#include "frontend_types.h"
a6352fd4	43	#include "shm.h"
852c2936 MD	44
	45	/* Buffer offset macros */
	46
	47	/* buf_trunc mask selects only the buffer number. */
	48	static inline
	49	unsigned long buf_trunc(unsigned long offset, struct channel *chan)
	50	{
	51	return offset & ~(chan->backend.buf_size - 1);
	52
	53	}
	54
	55	/* Select the buffer number value (counter). */
	56	static inline
	57	unsigned long buf_trunc_val(unsigned long offset, struct channel *chan)
	58	{
	59	return buf_trunc(offset, chan) >> chan->backend.buf_size_order;
	60	}
	61
	62	/* buf_offset mask selects only the offset within the current buffer. */
	63	static inline
	64	unsigned long buf_offset(unsigned long offset, struct channel *chan)
	65	{
	66	return offset & (chan->backend.buf_size - 1);
	67	}
	68
	69	/* subbuf_offset mask selects the offset within the current subbuffer. */
	70	static inline
	71	unsigned long subbuf_offset(unsigned long offset, struct channel *chan)
	72	{
	73	return offset & (chan->backend.subbuf_size - 1);
	74	}
	75
	76	/* subbuf_trunc mask selects the subbuffer number. */
	77	static inline
	78	unsigned long subbuf_trunc(unsigned long offset, struct channel *chan)
	79	{
	80	return offset & ~(chan->backend.subbuf_size - 1);
	81	}
	82
	83	/* subbuf_align aligns the offset to the next subbuffer. */
	84	static inline
	85	unsigned long subbuf_align(unsigned long offset, struct channel *chan)
	86	{
	87	return (offset + chan->backend.subbuf_size)
	88	& ~(chan->backend.subbuf_size - 1);
	89	}
	90
	91	/* subbuf_index returns the index of the current subbuffer within the buffer. */
	92	static inline
	93	unsigned long subbuf_index(unsigned long offset, struct channel *chan)
	94	{
	95	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
	96	}
	97
	98	/*
	99	* Last TSC comparison functions. Check if the current TSC overflows tsc_bits
	100	* bits from the last TSC read. When overflows are detected, the full 64-bit
	101	* timestamp counter should be written in the record header. Reads and writes
	102	* last_tsc atomically.
	103	*/
	104
14641deb	105	#if (CAA_BITS_PER_LONG == 32)
852c2936	106	static inline
4cfec15c	107	void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	108	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	109	{
	110	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	111	return;
	112
	113	/*
	114	* Ensure the compiler performs this update in a single instruction.
	115	*/
	116	v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits));
	117	}
	118
	119	static inline
4cfec15c	120	int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	121	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	122	{
	123	unsigned long tsc_shifted;
	124
	125	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	126	return 0;
	127
	128	tsc_shifted = (unsigned long)(tsc >> config->tsc_bits);
b5a3dfa5	129	if (caa_unlikely(tsc_shifted
852c2936 MD	130	- (unsigned long)v_read(config, &buf->last_tsc)))
	131	return 1;
	132	else
	133	return 0;
	134	}
	135	#else
	136	static inline
4cfec15c	137	void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	138	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	139	{
	140	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	141	return;
	142
	143	v_set(config, &buf->last_tsc, (unsigned long)tsc);
	144	}
	145
	146	static inline
4cfec15c	147	int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	148	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	149	{
	150	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	151	return 0;
	152
b5a3dfa5	153	if (caa_unlikely((tsc - v_read(config, &buf->last_tsc))
852c2936 MD	154	>> config->tsc_bits))
	155	return 1;
	156	else
	157	return 0;
	158	}
	159	#endif
	160
	161	extern
e56bb47c MD	162	int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx,
e56bb47c MD	163	void *client_ctx);
852c2936 MD	164
852c2936 MD	165	extern
4cfec15c	166	void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf,
1d498196	167	enum switch_mode mode,
38fae1d3	168	struct lttng_ust_shm_handle *handle);
852c2936	169
b07cd987 MD	170	void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config,
	171	struct lttng_ust_lib_ring_buffer *buf,
	172	struct channel *chan,
	173	unsigned long offset,
	174	unsigned long commit_count,
	175	unsigned long idx,
	176	struct lttng_ust_shm_handle *handle,
	177	uint64_t tsc);
	178
852c2936 MD	179	/* Buffer write helpers */
	180
	181	static inline
4cfec15c	182	void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf,
852c2936 MD	183	struct channel *chan,
	184	unsigned long offset)
	185	{
	186	unsigned long consumed_old, consumed_new;
	187
	188	do {
14641deb	189	consumed_old = uatomic_read(&buf->consumed);
852c2936 MD	190	/*
	191	* If buffer is in overwrite mode, push the reader consumed
	192	* count if the write position has reached it and we are not
	193	* at the first iteration (don't push the reader farther than
	194	* the writer). This operation can be done concurrently by many
	195	* writers in the same buffer, the writer being at the farthest
	196	* write position sub-buffer index in the buffer being the one
	197	* which will win this loop.
	198	*/
b5a3dfa5	199	if (caa_unlikely(subbuf_trunc(offset, chan)
852c2936 MD	200	- subbuf_trunc(consumed_old, chan)
	201	>= chan->backend.buf_size))
	202	consumed_new = subbuf_align(consumed_old, chan);
	203	else
	204	return;
b5a3dfa5	205	} while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
852c2936 MD	206	consumed_new) != consumed_old));
	207	}
	208
4c742ffd MD	209	/*
	210	* Move consumed position to the beginning of subbuffer in which the
	211	* write offset is. Should only be used on ring buffers that are not
	212	* actively being written into, because clear_reader does not take into
	213	* account the commit counters when moving the consumed position, which
	214	* can make concurrent trace producers or consumers observe consumed
	215	* position further than the write offset, which breaks ring buffer
	216	* algorithm guarantees.
	217	*/
beca55a1 MD	218	static inline
	219	void lib_ring_buffer_clear_reader(struct lttng_ust_lib_ring_buffer *buf,
	220	struct lttng_ust_shm_handle *handle)
	221	{
	222	struct channel *chan;
	223	const struct lttng_ust_lib_ring_buffer_config *config;
	224	unsigned long offset, consumed_old, consumed_new;
	225
	226	chan = shmp(handle, buf->backend.chan);
	227	if (!chan)
	228	return;
	229	config = &chan->backend.config;
	230
	231	do {
	232	offset = v_read(config, &buf->offset);
	233	consumed_old = uatomic_read(&buf->consumed);
4c742ffd MD	234	CHAN_WARN_ON(chan, (long) (subbuf_trunc(offset, chan)
	235	- subbuf_trunc(consumed_old, chan))
	236	< 0);
	237	consumed_new = subbuf_trunc(offset, chan);
beca55a1 MD	238	} while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
	239	consumed_new) != consumed_old));
	240	}
	241
852c2936	242	static inline
4cfec15c MD	243	int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	244	struct lttng_ust_lib_ring_buffer *buf,
852c2936 MD	245	struct channel *chan)
	246	{
	247	return !!subbuf_offset(v_read(config, &buf->offset), chan);
	248	}
	249
	250	static inline
4cfec15c MD	251	unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	252	struct lttng_ust_lib_ring_buffer *buf,
1d498196	253	unsigned long idx,
38fae1d3	254	struct lttng_ust_shm_handle *handle)
852c2936	255	{
1d498196	256	return subbuffer_get_data_size(config, &buf->backend, idx, handle);
852c2936 MD	257	}
	258
	259	/*
	260	* Check if all space reservation in a buffer have been committed. This helps
	261	* knowing if an execution context is nested (for per-cpu buffers only).
	262	* This is a very specific ftrace use-case, so we keep this as "internal" API.
	263	*/
	264	static inline
4cfec15c MD	265	int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	266	struct lttng_ust_lib_ring_buffer *buf,
1d498196	267	struct channel *chan,
38fae1d3	268	struct lttng_ust_shm_handle *handle)
852c2936 MD	269	{
852c2936 MD	270	unsigned long offset, idx, commit_count;
730be651	271	struct commit_counters_hot *cc_hot;
852c2936 MD	272
	273	CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
	274	CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);
	275
	276	/*
	277	* Read offset and commit count in a loop so they are both read
	278	* atomically wrt interrupts. By deal with interrupt concurrency by
	279	* restarting both reads if the offset has been pushed. Note that given
	280	* we only have to deal with interrupt concurrency here, an interrupt
	281	* modifying the commit count will also modify "offset", so it is safe
	282	* to only check for offset modifications.
	283	*/
	284	do {
	285	offset = v_read(config, &buf->offset);
	286	idx = subbuf_index(offset, chan);
730be651 MD	287	cc_hot = shmp_index(handle, buf->commit_hot, idx);
	288	if (caa_unlikely(!cc_hot))
	289	return 0;
15500a1b	290	commit_count = v_read(config, &cc_hot->cc);
852c2936 MD	291	} while (offset != v_read(config, &buf->offset));
	292
	293	return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
	294	- (commit_count & chan->commit_count_mask) == 0);
	295	}
	296
1b7b0501 MD	297	/*
	298	* Receive end of subbuffer TSC as parameter. It has been read in the
	299	* space reservation loop of either reserve or switch, which ensures it
	300	* progresses monotonically with event records in the buffer. Therefore,
	301	* it ensures that the end timestamp of a subbuffer is <= begin
	302	* timestamp of the following subbuffers.
	303	*/
852c2936	304	static inline
4cfec15c MD	305	void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	306	struct lttng_ust_lib_ring_buffer *buf,
852c2936 MD	307	struct channel *chan,
	308	unsigned long offset,
	309	unsigned long commit_count,
1d498196	310	unsigned long idx,
1b7b0501 MD	311	struct lttng_ust_shm_handle *handle,
1b7b0501 MD	312	uint64_t tsc)
852c2936 MD	313	{
	314	unsigned long old_commit_count = commit_count
	315	- chan->backend.subbuf_size;
852c2936 MD	316
852c2936 MD	317	/* Check if all commits have been done */
b5a3dfa5	318	if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
b07cd987 MD	319	- (old_commit_count & chan->commit_count_mask) == 0))
	320	lib_ring_buffer_check_deliver_slow(config, buf, chan, offset,
	321	commit_count, idx, handle, tsc);
852c2936 MD	322	}
	323
	324	/*
	325	* lib_ring_buffer_write_commit_counter
	326	*
	327	* For flight recording. must be called after commit.
	328	* This function increments the subbuffer's commit_seq counter each time the
	329	* commit count reaches back the reserve offset (modulo subbuffer size). It is
	330	* useful for crash dump.
	331	*/
	332	static inline
4cfec15c MD	333	void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	334	struct lttng_ust_lib_ring_buffer *buf,
852c2936	335	struct channel *chan,
852c2936 MD	336	unsigned long buf_offset,
852c2936 MD	337	unsigned long commit_count,
d2fe4771 MD	338	struct lttng_ust_shm_handle *handle,
d2fe4771 MD	339	struct commit_counters_hot *cc_hot)
852c2936	340	{
80249235	341	unsigned long commit_seq_old;
852c2936 MD	342
	343	if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
	344	return;
	345
852c2936 MD	346	/*
	347	* subbuf_offset includes commit_count_mask. We can simply
	348	* compare the offsets within the subbuffer without caring about
	349	* buffer full/empty mismatch because offset is never zero here
	350	* (subbuffer header and record headers have non-zero length).
	351	*/
80249235	352	if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan)))
852c2936 MD	353	return;
852c2936 MD	354
d2fe4771	355	commit_seq_old = v_read(config, &cc_hot->seq);
16ec84c8	356	if (caa_likely((long) (commit_seq_old - commit_count) < 0))
d2fe4771	357	v_set(config, &cc_hot->seq, commit_count);
852c2936 MD	358	}
852c2936 MD	359
4cfec15c	360	extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf,
a6352fd4	361	struct channel_backend *chanb, int cpu,
38fae1d3	362	struct lttng_ust_shm_handle *handle,
1d498196	363	struct shm_object *shmobj);
4cfec15c	364	extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf,
38fae1d3	365	struct lttng_ust_shm_handle *handle);
852c2936 MD	366
852c2936 MD	367	/* Keep track of trap nesting inside ring buffer code */
8c90a710	368	extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting);
852c2936	369
e92f3e28	370	#endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */