[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 <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);

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));
}

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);
		if (caa_unlikely(subbuf_trunc(offset, chan)
			      - subbuf_trunc(consumed_old, chan)
			     > 0))
			consumed_new = subbuf_trunc(offset, chan);
		else
			return;
	} 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 = shmp_index(handle, buf->commit_hot, idx);

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

	if (caa_unlikely(!cc_hot))
		return 0;

	/*
	 * 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, &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 MD	36	#include <signal.h>
2c44f5b9 MD	37	#include <pthread.h>
14641deb	38
4318ae1b	39	#include <lttng/ringbuffer-config.h>
4931a13e MD	40	#include "backend_types.h"
4931a13e MD	41	#include "frontend_types.h"
a6352fd4	42	#include "shm.h"
852c2936 MD	43
	44	/* Buffer offset macros */
	45
	46	/* buf_trunc mask selects only the buffer number. */
	47	static inline
	48	unsigned long buf_trunc(unsigned long offset, struct channel *chan)
	49	{
	50	return offset & ~(chan->backend.buf_size - 1);
	51
	52	}
	53
	54	/* Select the buffer number value (counter). */
	55	static inline
	56	unsigned long buf_trunc_val(unsigned long offset, struct channel *chan)
	57	{
	58	return buf_trunc(offset, chan) >> chan->backend.buf_size_order;
	59	}
	60
	61	/* buf_offset mask selects only the offset within the current buffer. */
	62	static inline
	63	unsigned long buf_offset(unsigned long offset, struct channel *chan)
	64	{
	65	return offset & (chan->backend.buf_size - 1);
	66	}
	67
	68	/* subbuf_offset mask selects the offset within the current subbuffer. */
	69	static inline
	70	unsigned long subbuf_offset(unsigned long offset, struct channel *chan)
	71	{
	72	return offset & (chan->backend.subbuf_size - 1);
	73	}
	74
	75	/* subbuf_trunc mask selects the subbuffer number. */
	76	static inline
	77	unsigned long subbuf_trunc(unsigned long offset, struct channel *chan)
	78	{
	79	return offset & ~(chan->backend.subbuf_size - 1);
	80	}
	81
	82	/* subbuf_align aligns the offset to the next subbuffer. */
	83	static inline
	84	unsigned long subbuf_align(unsigned long offset, struct channel *chan)
	85	{
	86	return (offset + chan->backend.subbuf_size)
	87	& ~(chan->backend.subbuf_size - 1);
	88	}
	89
	90	/* subbuf_index returns the index of the current subbuffer within the buffer. */
	91	static inline
	92	unsigned long subbuf_index(unsigned long offset, struct channel *chan)
	93	{
	94	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
	95	}
	96
	97	/*
	98	* Last TSC comparison functions. Check if the current TSC overflows tsc_bits
	99	* bits from the last TSC read. When overflows are detected, the full 64-bit
	100	* timestamp counter should be written in the record header. Reads and writes
	101	* last_tsc atomically.
	102	*/
	103
14641deb	104	#if (CAA_BITS_PER_LONG == 32)
852c2936	105	static inline
4cfec15c	106	void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	107	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	108	{
	109	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	110	return;
	111
	112	/*
	113	* Ensure the compiler performs this update in a single instruction.
	114	*/
	115	v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits));
	116	}
	117
	118	static inline
4cfec15c	119	int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	120	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	121	{
	122	unsigned long tsc_shifted;
	123
	124	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	125	return 0;
	126
	127	tsc_shifted = (unsigned long)(tsc >> config->tsc_bits);
b5a3dfa5	128	if (caa_unlikely(tsc_shifted
852c2936 MD	129	- (unsigned long)v_read(config, &buf->last_tsc)))
	130	return 1;
	131	else
	132	return 0;
	133	}
	134	#else
	135	static inline
4cfec15c	136	void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	137	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	138	{
	139	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	140	return;
	141
	142	v_set(config, &buf->last_tsc, (unsigned long)tsc);
	143	}
	144
	145	static inline
4cfec15c	146	int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,
2fed87ae	147	struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)
852c2936 MD	148	{
	149	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
	150	return 0;
	151
b5a3dfa5	152	if (caa_unlikely((tsc - v_read(config, &buf->last_tsc))
852c2936 MD	153	>> config->tsc_bits))
	154	return 1;
	155	else
	156	return 0;
	157	}
	158	#endif
	159
	160	extern
4cfec15c	161	int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx);
852c2936 MD	162
852c2936 MD	163	extern
4cfec15c	164	void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf,
1d498196	165	enum switch_mode mode,
38fae1d3	166	struct lttng_ust_shm_handle *handle);
852c2936	167
b07cd987 MD	168	void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_lib_ring_buffer_config *config,
	169	struct lttng_ust_lib_ring_buffer *buf,
	170	struct channel *chan,
	171	unsigned long offset,
	172	unsigned long commit_count,
	173	unsigned long idx,
	174	struct lttng_ust_shm_handle *handle,
	175	uint64_t tsc);
	176
852c2936 MD	177	/* Buffer write helpers */
	178
	179	static inline
4cfec15c	180	void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf,
852c2936 MD	181	struct channel *chan,
	182	unsigned long offset)
	183	{
	184	unsigned long consumed_old, consumed_new;
	185
	186	do {
14641deb	187	consumed_old = uatomic_read(&buf->consumed);
852c2936 MD	188	/*
	189	* If buffer is in overwrite mode, push the reader consumed
	190	* count if the write position has reached it and we are not
	191	* at the first iteration (don't push the reader farther than
	192	* the writer). This operation can be done concurrently by many
	193	* writers in the same buffer, the writer being at the farthest
	194	* write position sub-buffer index in the buffer being the one
	195	* which will win this loop.
	196	*/
b5a3dfa5	197	if (caa_unlikely(subbuf_trunc(offset, chan)
852c2936 MD	198	- subbuf_trunc(consumed_old, chan)
	199	>= chan->backend.buf_size))
	200	consumed_new = subbuf_align(consumed_old, chan);
	201	else
	202	return;
b5a3dfa5	203	} while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
852c2936 MD	204	consumed_new) != consumed_old));
	205	}
	206
a94d430f MD	207	static inline
	208	void lib_ring_buffer_clear_reader(struct lttng_ust_lib_ring_buffer *buf,
	209	struct lttng_ust_shm_handle *handle)
	210	{
	211	struct channel *chan;
	212	const struct lttng_ust_lib_ring_buffer_config *config;
	213	unsigned long offset, consumed_old, consumed_new;
	214
	215	chan = shmp(handle, buf->backend.chan);
	216	if (!chan)
	217	return;
	218	config = &chan->backend.config;
	219
	220	do {
	221	offset = v_read(config, &buf->offset);
	222	consumed_old = uatomic_read(&buf->consumed);
	223	if (caa_unlikely(subbuf_trunc(offset, chan)
	224	- subbuf_trunc(consumed_old, chan)
	225	> 0))
	226	consumed_new = subbuf_trunc(offset, chan);
	227	else
	228	return;
	229	} while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
	230	consumed_new) != consumed_old));
	231	}
	232
852c2936	233	static inline
4cfec15c MD	234	int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	235	struct lttng_ust_lib_ring_buffer *buf,
852c2936 MD	236	struct channel *chan)
	237	{
	238	return !!subbuf_offset(v_read(config, &buf->offset), chan);
	239	}
	240
	241	static inline
4cfec15c MD	242	unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	243	struct lttng_ust_lib_ring_buffer *buf,
1d498196	244	unsigned long idx,
38fae1d3	245	struct lttng_ust_shm_handle *handle)
852c2936	246	{
1d498196	247	return subbuffer_get_data_size(config, &buf->backend, idx, handle);
852c2936 MD	248	}
	249
	250	/*
	251	* Check if all space reservation in a buffer have been committed. This helps
	252	* knowing if an execution context is nested (for per-cpu buffers only).
	253	* This is a very specific ftrace use-case, so we keep this as "internal" API.
	254	*/
	255	static inline
4cfec15c MD	256	int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	257	struct lttng_ust_lib_ring_buffer *buf,
1d498196	258	struct channel *chan,
38fae1d3	259	struct lttng_ust_shm_handle *handle)
852c2936 MD	260	{
852c2936 MD	261	unsigned long offset, idx, commit_count;
15500a1b	262	struct commit_counters_hot *cc_hot = shmp_index(handle, buf->commit_hot, idx);
852c2936 MD	263
	264	CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
	265	CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);
	266
15500a1b MD	267	if (caa_unlikely(!cc_hot))
	268	return 0;
	269
852c2936 MD	270	/*
	271	* Read offset and commit count in a loop so they are both read
	272	* atomically wrt interrupts. By deal with interrupt concurrency by
	273	* restarting both reads if the offset has been pushed. Note that given
	274	* we only have to deal with interrupt concurrency here, an interrupt
	275	* modifying the commit count will also modify "offset", so it is safe
	276	* to only check for offset modifications.
	277	*/
	278	do {
	279	offset = v_read(config, &buf->offset);
	280	idx = subbuf_index(offset, chan);
15500a1b	281	commit_count = v_read(config, &cc_hot->cc);
852c2936 MD	282	} while (offset != v_read(config, &buf->offset));
	283
	284	return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
	285	- (commit_count & chan->commit_count_mask) == 0);
	286	}
	287
1b7b0501 MD	288	/*
	289	* Receive end of subbuffer TSC as parameter. It has been read in the
	290	* space reservation loop of either reserve or switch, which ensures it
	291	* progresses monotonically with event records in the buffer. Therefore,
	292	* it ensures that the end timestamp of a subbuffer is <= begin
	293	* timestamp of the following subbuffers.
	294	*/
852c2936	295	static inline
4cfec15c MD	296	void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	297	struct lttng_ust_lib_ring_buffer *buf,
852c2936 MD	298	struct channel *chan,
	299	unsigned long offset,
	300	unsigned long commit_count,
1d498196	301	unsigned long idx,
1b7b0501 MD	302	struct lttng_ust_shm_handle *handle,
1b7b0501 MD	303	uint64_t tsc)
852c2936 MD	304	{
	305	unsigned long old_commit_count = commit_count
	306	- chan->backend.subbuf_size;
852c2936 MD	307
852c2936 MD	308	/* Check if all commits have been done */
b5a3dfa5	309	if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
b07cd987 MD	310	- (old_commit_count & chan->commit_count_mask) == 0))
	311	lib_ring_buffer_check_deliver_slow(config, buf, chan, offset,
	312	commit_count, idx, handle, tsc);
852c2936 MD	313	}
	314
	315	/*
	316	* lib_ring_buffer_write_commit_counter
	317	*
	318	* For flight recording. must be called after commit.
	319	* This function increments the subbuffer's commit_seq counter each time the
	320	* commit count reaches back the reserve offset (modulo subbuffer size). It is
	321	* useful for crash dump.
	322	*/
	323	static inline
4cfec15c MD	324	void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config,
4cfec15c MD	325	struct lttng_ust_lib_ring_buffer *buf,
852c2936	326	struct channel *chan,
852c2936 MD	327	unsigned long buf_offset,
852c2936 MD	328	unsigned long commit_count,
d2fe4771 MD	329	struct lttng_ust_shm_handle *handle,
d2fe4771 MD	330	struct commit_counters_hot *cc_hot)
852c2936	331	{
80249235	332	unsigned long commit_seq_old;
852c2936 MD	333
	334	if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
	335	return;
	336
852c2936 MD	337	/*
	338	* subbuf_offset includes commit_count_mask. We can simply
	339	* compare the offsets within the subbuffer without caring about
	340	* buffer full/empty mismatch because offset is never zero here
	341	* (subbuffer header and record headers have non-zero length).
	342	*/
80249235	343	if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan)))
852c2936 MD	344	return;
852c2936 MD	345
d2fe4771	346	commit_seq_old = v_read(config, &cc_hot->seq);
16ec84c8	347	if (caa_likely((long) (commit_seq_old - commit_count) < 0))
d2fe4771	348	v_set(config, &cc_hot->seq, commit_count);
852c2936 MD	349	}
852c2936 MD	350
4cfec15c	351	extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf,
a6352fd4	352	struct channel_backend *chanb, int cpu,
38fae1d3	353	struct lttng_ust_shm_handle *handle,
1d498196	354	struct shm_object *shmobj);
4cfec15c	355	extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf,
38fae1d3	356	struct lttng_ust_shm_handle *handle);
852c2936 MD	357
852c2936 MD	358	/* Keep track of trap nesting inside ring buffer code */
8c90a710	359	extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting);
852c2936	360
e92f3e28	361	#endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */