1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Author: SeongJae Park <sj@kernel.org>
4  */
5 #define _GNU_SOURCE
6 
7 #include <fcntl.h>
8 #include <stdbool.h>
9 #include <stdint.h>
10 #include <stdio.h>
11 #include <stdlib.h>
12 #include <sys/types.h>
13 #include <sys/wait.h>
14 #include <time.h>
15 #include <unistd.h>
16 
17 #define DBGFS_MONITOR_ON "/sys/kernel/debug/damon/monitor_on_DEPRECATED"
18 #define DBGFS_TARGET_IDS "/sys/kernel/debug/damon/target_ids"
19 
turn_damon_on_exit(void)20 static void turn_damon_on_exit(void)
21 {
22 	int target_ids_fd = open(DBGFS_TARGET_IDS, O_RDWR);
23 	int monitor_on_fd = open(DBGFS_MONITOR_ON, O_RDWR);
24 	char pid_str[128];
25 
26 	snprintf(pid_str, sizeof(pid_str), "%d", getpid());
27 	write(target_ids_fd, pid_str, sizeof(pid_str));
28 	write(monitor_on_fd, "on\n", 3);
29 	close(target_ids_fd);
30 	close(monitor_on_fd);
31 	usleep(1000);
32 	exit(0);
33 }
34 
try_race(void)35 static void try_race(void)
36 {
37 	int target_ids_fd = open(DBGFS_TARGET_IDS, O_RDWR);
38 	int pid = fork();
39 	int buf[256];
40 
41 	if (pid < 0) {
42 		fprintf(stderr, "fork() failed\n");
43 		exit(1);
44 	}
45 	if (pid == 0)
46 		turn_damon_on_exit();
47 	while (true) {
48 		int status;
49 
50 		read(target_ids_fd, buf, sizeof(buf));
51 		if (waitpid(-1, &status, WNOHANG) == pid)
52 			break;
53 	}
54 	close(target_ids_fd);
55 }
56 
ts_to_ms(struct timespec * ts)57 static inline uint64_t ts_to_ms(struct timespec *ts)
58 {
59 	return (uint64_t)ts->tv_sec * 1000 + (uint64_t)ts->tv_nsec / 1000000;
60 }
61 
main(int argc,char * argv[])62 int main(int argc, char *argv[])
63 {
64 	struct timespec start_time, now;
65 	int runtime_ms;
66 
67 	if (argc != 2) {
68 		fprintf(stderr, "Usage: %s <runtime in ms>\n", argv[0]);
69 		exit(1);
70 	}
71 	runtime_ms = atoi(argv[1]);
72 	clock_gettime(CLOCK_MONOTONIC, &start_time);
73 	while (true) {
74 		try_race();
75 		clock_gettime(CLOCK_MONOTONIC, &now);
76 		if (ts_to_ms(&now) - ts_to_ms(&start_time) > runtime_ms)
77 			break;
78 	}
79 	return 0;
80 }
81