tools/perf/util/mmap.h

#ifndef __PERF_MMAP_H
#define __PERF_MMAP_H 1

#include <linux/compiler.h>
#include <linux/refcount.h>
#include <linux/types.h>
#include <asm/barrier.h>
#include <stdbool.h>
#include "auxtrace.h"
#include "event.h"

/**
 * struct perf_mmap - perf's ring buffer mmap details
 *
 * @refcnt - e.g. code using PERF_EVENT_IOC_SET_OUTPUT to share this
 */
struct perf_mmap {
	void		 *base;
	int		 mask;
	int		 fd;
	refcount_t	 refcnt;
	u64		 prev;
	struct auxtrace_mmap auxtrace_mmap;
	char		 event_copy[PERF_SAMPLE_MAX_SIZE] __aligned(8);
};

/*
 * State machine of bkw_mmap_state:
 *
 *                     .________________(forbid)_____________.
 *                     |                                     V
 * NOTREADY --(0)--> RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
 *                     ^  ^              |   ^               |
 *                     |  |__(forbid)____/   |___(forbid)___/|
 *                     |                                     |
 *                      \_________________(3)_______________/
 *
 * NOTREADY     : Backward ring buffers are not ready
 * RUNNING      : Backward ring buffers are recording
 * DATA_PENDING : We are required to collect data from backward ring buffers
 * EMPTY        : We have collected data from backward ring buffers.
 *
 * (0): Setup backward ring buffer
 * (1): Pause ring buffers for reading
 * (2): Read from ring buffers
 * (3): Resume ring buffers for recording
 */
enum bkw_mmap_state {
	BKW_MMAP_NOTREADY,
	BKW_MMAP_RUNNING,
	BKW_MMAP_DATA_PENDING,
	BKW_MMAP_EMPTY,
};

struct mmap_params {
	int			    prot, mask;
	struct auxtrace_mmap_params auxtrace_mp;
};

int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd);
void perf_mmap__munmap(struct perf_mmap *map);

void perf_mmap__get(struct perf_mmap *map);
void perf_mmap__put(struct perf_mmap *map);

void perf_mmap__consume(struct perf_mmap *map, bool overwrite);

void perf_mmap__read_catchup(struct perf_mmap *md);

static inline u64 perf_mmap__read_head(struct perf_mmap *mm)
{
	struct perf_event_mmap_page *pc = mm->base;
	u64 head = ACCESS_ONCE(pc->data_head);
	rmb();
	return head;
}

static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
{
	struct perf_event_mmap_page *pc = md->base;

	/*
	 * ensure all reads are done before we write the tail out.
	 */
	mb();
	pc->data_tail = tail;
}

union perf_event *perf_mmap__read_forward(struct perf_mmap *map, bool check_messup);
union perf_event *perf_mmap__read_backward(struct perf_mmap *map);

size_t perf_mmap__mmap_len(struct perf_mmap *map);

#endif /*__PERF_MMAP_H */