1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_COOKIE_H
3#define __LINUX_COOKIE_H
4
5#include <linux/atomic.h>
6#include <linux/percpu.h>
7#include <asm/local.h>
8
9struct pcpu_gen_cookie {
10	local_t nesting;
11	u64 last;
12} __aligned(16);
13
14struct gen_cookie {
15	struct pcpu_gen_cookie __percpu *local;
16	atomic64_t forward_last ____cacheline_aligned_in_smp;
17	atomic64_t reverse_last;
18};
19
20#define COOKIE_LOCAL_BATCH	4096
21
22#define DEFINE_COOKIE(name)						\
23	static DEFINE_PER_CPU(struct pcpu_gen_cookie, __##name);	\
24	static struct gen_cookie name = {				\
25		.local		= &__##name,				\
26		.forward_last	= ATOMIC64_INIT(0),			\
27		.reverse_last	= ATOMIC64_INIT(0),			\
28	}
29
30static __always_inline u64 gen_cookie_next(struct gen_cookie *gc)
31{
32	struct pcpu_gen_cookie *local = this_cpu_ptr(gc->local);
33	u64 val;
34
35	if (likely(local_inc_return(&local->nesting) == 1)) {
36		val = local->last;
37		if (__is_defined(CONFIG_SMP) &&
38		    unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0)) {
39			s64 next = atomic64_add_return(COOKIE_LOCAL_BATCH,
40						       &gc->forward_last);
41			val = next - COOKIE_LOCAL_BATCH;
42		}
43		local->last = ++val;
44	} else {
45		val = atomic64_dec_return(&gc->reverse_last);
46	}
47	local_dec(&local->nesting);
48	return val;
49}
50
51#endif /* __LINUX_COOKIE_H */
52