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
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#define CLOCK_MONOTONIC 1
char _license[] SEC("license") = "GPL";
struct elem {
struct bpf_timer timer;
};
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 1);
__type(key, int);
__type(value, struct elem);
} timer_map SEC(".maps");
volatile int in_timer_start;
volatile int tp_called;
static int timer_cb(void *map, int *key, struct elem *value)
{
return 0;
}
SEC("tp_btf/hrtimer_cancel")
int BPF_PROG(tp_hrtimer_cancel, struct hrtimer *hrtimer)
{
struct bpf_timer *timer;
int key = 0;
if (!in_timer_start)
return 0;
tp_called = 1;
timer = bpf_map_lookup_elem(&timer_map, &key);
/*
* Call bpf_timer_start() from the tracepoint within hrtimer logic
* on the same timer to make sure it doesn't deadlock.
*/
bpf_timer_start(timer, 1000000000, 0);
return 0;
}
SEC("syscall")
int start_timer(void *ctx)
{
struct bpf_timer *timer;
int key = 0;
timer = bpf_map_lookup_elem(&timer_map, &key);
/* claude may complain here that there is no NULL check. Ignoring it. */
bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC);
bpf_timer_set_callback(timer, timer_cb);
/*
* call hrtimer_start() twice, so that 2nd call does
* remove_hrtimer() and trace_hrtimer_cancel() tracepoint.
*/
in_timer_start = 1;
bpf_timer_start(timer, 1000000000, 0);
bpf_timer_start(timer, 1000000000, 0);
in_timer_start = 0;
return 0;
}
|
