summaryrefslogtreecommitdiff
path: root/lib/seqlock.h
blob: 762b6ec1d2dc7fa7ba5df9fe75d4e28da9a1c53b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
#ifndef FIO_SEQLOCK_H
#define FIO_SEQLOCK_H

#include "types.h"
#include "../arch/arch.h"

struct seqlock {
	volatile int sequence;
};

static inline void seqlock_init(struct seqlock *s)
{
	s->sequence = 0;
}

static inline unsigned int read_seqlock_begin(struct seqlock *s)
{
	unsigned int seq;

	do {
		seq = s->sequence;
		if (!(seq & 1))
			break;
		nop;
	} while (1);

	read_barrier();
	return seq;
}

static inline bool read_seqlock_retry(struct seqlock *s, unsigned int seq)
{
	read_barrier();
	return s->sequence != seq;
}

static inline void write_seqlock_begin(struct seqlock *s)
{
	s->sequence++;
	write_barrier();
}

static inline void write_seqlock_end(struct seqlock *s)
{
	write_barrier();
	s->sequence++;
}

#endif