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

/* SPDX-License-Identifier: (GPL-2.0 OR LGPL-2.1)
 *
 * linux/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 <wrapper/ringbuffer/config.h>
#include <wrapper/ringbuffer/backend_types.h>
#include <wrapper/ringbuffer/frontend_types.h>
#include <lib/prio_heap/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 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 (BITS_PER_LONG == 32)
static inline
void save_last_tsc(const struct lib_ring_buffer_config *config,
		   struct lib_ring_buffer *buf, u64 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 lib_ring_buffer_config *config,
		      struct lib_ring_buffer *buf, u64 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 (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 lib_ring_buffer_config *config,
		   struct lib_ring_buffer *buf, u64 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 lib_ring_buffer_config *config,
		      struct lib_ring_buffer *buf, u64 tsc)
{
	if (config->tsc_bits == 0 || config->tsc_bits == 64)
		return 0;

	if (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 lib_ring_buffer_ctx *ctx,
		void *client_ctx);

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

extern
void lib_ring_buffer_check_deliver_slow(const struct lib_ring_buffer_config *config,
				   struct lib_ring_buffer *buf,
			           struct channel *chan,
			           unsigned long offset,
				   unsigned long commit_count,
			           unsigned long idx,
				   u64 tsc);

extern
void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf);
extern
void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf);

/* Buffer write helpers */

static inline
void lib_ring_buffer_reserve_push_reader(struct lib_ring_buffer *buf,
					 struct 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));
}

static inline
int lib_ring_buffer_pending_data(const struct lib_ring_buffer_config *config,
				 struct 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 lib_ring_buffer_config *config,
					    struct lib_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 lib_ring_buffer_config *config,
				      struct lib_ring_buffer *buf,
				      struct 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 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 lib_ring_buffer_config *config,
				   struct lib_ring_buffer *buf,
			           struct channel *chan,
			           unsigned long offset,
				   unsigned long commit_count,
			           unsigned long idx,
				   u64 tsc)
{
	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, 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 lib_ring_buffer_config *config,
					  struct lib_ring_buffer *buf,
				          struct 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 lib_ring_buffer *buf,
				  struct channel_backend *chanb, int cpu);
extern void lib_ring_buffer_free(struct lib_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
9f36eaed MJ	1	/* SPDX-License-Identifier: (GPL-2.0 OR LGPL-2.1)
9f36eaed MJ	2	*
f3bc08c5 MD	3	* linux/ringbuffer/frontend_internal.h
f3bc08c5 MD	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
5671a661 MD	15	#include <wrapper/ringbuffer/config.h>
	16	#include <wrapper/ringbuffer/backend_types.h>
	17	#include <wrapper/ringbuffer/frontend_types.h>
	18	#include <lib/prio_heap/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
	24	unsigned long buf_trunc(unsigned long offset, struct channel *chan)
	25	{
	26	return offset & ~(chan->backend.buf_size - 1);
	27
	28	}
	29
	30	/* Select the buffer number value (counter). */
	31	static inline
	32	unsigned long buf_trunc_val(unsigned long offset, struct channel *chan)
	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
	39	unsigned long buf_offset(unsigned long offset, struct channel *chan)
	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
	46	unsigned long subbuf_offset(unsigned long offset, struct channel *chan)
	47	{
	48	return offset & (chan->backend.subbuf_size - 1);
	49	}
	50
	51	/* subbuf_trunc mask selects the subbuffer number. */
	52	static inline
	53	unsigned long subbuf_trunc(unsigned long offset, struct channel *chan)
	54	{
	55	return offset & ~(chan->backend.subbuf_size - 1);
	56	}
	57
	58	/* subbuf_align aligns the offset to the next subbuffer. */
	59	static inline
	60	unsigned long subbuf_align(unsigned long offset, struct channel *chan)
	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
	68	unsigned long subbuf_index(unsigned long offset, struct channel *chan)
	69	{
	70	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;
	71	}
	72
	73	/*
	74	* Last TSC comparison functions. Check if the current TSC overflows tsc_bits
	75	* bits from the last TSC read. When overflows are detected, the full 64-bit
	76	* timestamp counter should be written in the record header. Reads and writes
	77	* last_tsc atomically.
	78	*/
	79
	80	#if (BITS_PER_LONG == 32)
	81	static inline
	82	void save_last_tsc(const struct lib_ring_buffer_config *config,
83	struct lib_ring_buffer *buf, u64 tsc)
84	{
85	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
86	return;
87
88	/*
89	* Ensure the compiler performs this update in a single instruction.
90	*/
91	v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits));
92	}
93
94	static inline
95	int last_tsc_overflow(const struct lib_ring_buffer_config *config,
96	struct lib_ring_buffer *buf, u64 tsc)
97	{
98	unsigned long tsc_shifted;
99
100	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
101	return 0;
102
103	tsc_shifted = (unsigned long)(tsc >> config->tsc_bits);
104	if (unlikely(tsc_shifted
105	- (unsigned long)v_read(config, &buf->last_tsc)))
106	return 1;
107	else
108	return 0;
109	}
110	#else
111	static inline
112	void save_last_tsc(const struct lib_ring_buffer_config *config,
113	struct lib_ring_buffer *buf, u64 tsc)
114	{
115	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
116	return;
117
118	v_set(config, &buf->last_tsc, (unsigned long)tsc);
119	}
120
121	static inline
122	int last_tsc_overflow(const struct lib_ring_buffer_config *config,
123	struct lib_ring_buffer *buf, u64 tsc)
124	{
125	if (config->tsc_bits == 0 \|\| config->tsc_bits == 64)
126	return 0;
127
128	if (unlikely((tsc - v_read(config, &buf->last_tsc))
129	>> config->tsc_bits))
130	return 1;
131	else
132	return 0;
133	}
134	#endif
135
136	extern
cc62f29e MD	137	int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx,
cc62f29e MD	138	void *client_ctx);
f3bc08c5 MD	139
	140	extern
	141	void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf,
	142	enum switch_mode mode);
	143
aece661f MD	144	extern
	145	void lib_ring_buffer_check_deliver_slow(const struct lib_ring_buffer_config *config,
	146	struct lib_ring_buffer *buf,
	147	struct channel *chan,
	148	unsigned long offset,
	149	unsigned long commit_count,
	150	unsigned long idx,
	151	u64 tsc);
	152
5e391252 MD	153	extern
5e391252 MD	154	void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf);
c6f05468 MD	155	extern
c6f05468 MD	156	void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf);
5e391252	157
f3bc08c5 MD	158	/* Buffer write helpers */
	159
	160	static inline
	161	void lib_ring_buffer_reserve_push_reader(struct lib_ring_buffer *buf,
	162	struct channel *chan,
	163	unsigned long offset)
	164	{
	165	unsigned long consumed_old, consumed_new;
	166
	167	do {
	168	consumed_old = atomic_long_read(&buf->consumed);
	169	/*
	170	* If buffer is in overwrite mode, push the reader consumed
	171	* count if the write position has reached it and we are not
	172	* at the first iteration (don't push the reader farther than
	173	* the writer). This operation can be done concurrently by many
	174	* writers in the same buffer, the writer being at the farthest
	175	* write position sub-buffer index in the buffer being the one
	176	* which will win this loop.
	177	*/
	178	if (unlikely(subbuf_trunc(offset, chan)
	179	- subbuf_trunc(consumed_old, chan)
	180	>= chan->backend.buf_size))
	181	consumed_new = subbuf_align(consumed_old, chan);
	182	else
	183	return;
	184	} while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
	185	consumed_new) != consumed_old));
	186	}
	187
f3bc08c5 MD	188	static inline
	189	int lib_ring_buffer_pending_data(const struct lib_ring_buffer_config *config,
	190	struct lib_ring_buffer *buf,
	191	struct channel *chan)
	192	{
	193	return !!subbuf_offset(v_read(config, &buf->offset), chan);
	194	}
	195
	196	static inline
	197	unsigned long lib_ring_buffer_get_data_size(const struct lib_ring_buffer_config *config,
	198	struct lib_ring_buffer *buf,
	199	unsigned long idx)
	200	{
	201	return subbuffer_get_data_size(config, &buf->backend, idx);
	202	}
	203
	204	/*
	205	* Check if all space reservation in a buffer have been committed. This helps
	206	* knowing if an execution context is nested (for per-cpu buffers only).
	207	* This is a very specific ftrace use-case, so we keep this as "internal" API.
	208	*/
	209	static inline
	210	int lib_ring_buffer_reserve_committed(const struct lib_ring_buffer_config *config,
	211	struct lib_ring_buffer *buf,
	212	struct channel *chan)
	213	{
	214	unsigned long offset, idx, commit_count;
	215
	216	CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
	217	CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);
	218
	219	/*
	220	* Read offset and commit count in a loop so they are both read
	221	* atomically wrt interrupts. By deal with interrupt concurrency by
	222	* restarting both reads if the offset has been pushed. Note that given
	223	* we only have to deal with interrupt concurrency here, an interrupt
	224	* modifying the commit count will also modify "offset", so it is safe
	225	* to only check for offset modifications.
	226	*/
	227	do {
	228	offset = v_read(config, &buf->offset);
	229	idx = subbuf_index(offset, chan);
	230	commit_count = v_read(config, &buf->commit_hot[idx].cc);
	231	} while (offset != v_read(config, &buf->offset));
	232
	233	return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
	234	- (commit_count & chan->commit_count_mask) == 0);
	235	}
	236
635e457c MD	237	/*
	238	* Receive end of subbuffer TSC as parameter. It has been read in the
	239	* space reservation loop of either reserve or switch, which ensures it
	240	* progresses monotonically with event records in the buffer. Therefore,
	241	* it ensures that the end timestamp of a subbuffer is <= begin
	242	* timestamp of the following subbuffers.
	243	*/
f3bc08c5 MD	244	static inline
	245	void lib_ring_buffer_check_deliver(const struct lib_ring_buffer_config *config,
	246	struct lib_ring_buffer *buf,
	247	struct channel *chan,
	248	unsigned long offset,
	249	unsigned long commit_count,
635e457c MD	250	unsigned long idx,
635e457c MD	251	u64 tsc)
f3bc08c5 MD	252	{
	253	unsigned long old_commit_count = commit_count
	254	- chan->backend.subbuf_size;
f3bc08c5 MD	255
	256	/* Check if all commits have been done */
	257	if (unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
aece661f MD	258	- (old_commit_count & chan->commit_count_mask) == 0))
	259	lib_ring_buffer_check_deliver_slow(config, buf, chan, offset,
	260	commit_count, idx, tsc);
f3bc08c5 MD	261	}
	262
	263	/*
	264	* lib_ring_buffer_write_commit_counter
	265	*
	266	* For flight recording. must be called after commit.
	267	* This function increments the subbuffer's commit_seq counter each time the
	268	* commit count reaches back the reserve offset (modulo subbuffer size). It is
	269	* useful for crash dump.
	270	*/
	271	static inline
	272	void lib_ring_buffer_write_commit_counter(const struct lib_ring_buffer_config *config,
	273	struct lib_ring_buffer *buf,
	274	struct channel *chan,
f3bc08c5	275	unsigned long buf_offset,
8ec496cf MD	276	unsigned long commit_count,
8ec496cf MD	277	struct commit_counters_hot *cc_hot)
f3bc08c5	278	{
7915e163	279	unsigned long commit_seq_old;
f3bc08c5 MD	280
	281	if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
	282	return;
	283
f3bc08c5 MD	284	/*
	285	* subbuf_offset includes commit_count_mask. We can simply
	286	* compare the offsets within the subbuffer without caring about
	287	* buffer full/empty mismatch because offset is never zero here
	288	* (subbuffer header and record headers have non-zero length).
	289	*/
7915e163	290	if (unlikely(subbuf_offset(buf_offset - commit_count, chan)))
f3bc08c5 MD	291	return;
f3bc08c5 MD	292
8ec496cf	293	commit_seq_old = v_read(config, &cc_hot->seq);
6212b6b6	294	if (likely((long) (commit_seq_old - commit_count) < 0))
8ec496cf	295	v_set(config, &cc_hot->seq, commit_count);
f3bc08c5 MD	296	}
	297
	298	extern int lib_ring_buffer_create(struct lib_ring_buffer *buf,
	299	struct channel_backend *chanb, int cpu);
	300	extern void lib_ring_buffer_free(struct lib_ring_buffer *buf);
	301
	302	/* Keep track of trap nesting inside ring buffer code */
	303	DECLARE_PER_CPU(unsigned int, lib_ring_buffer_nesting);
	304
886d51a3	305	#endif /* _LIB_RING_BUFFER_FRONTEND_INTERNAL_H */