1/* vi: set sw=4 ts=4: */
2/*
3 * chrt - manipulate real-time attributes of a process
4 * Copyright (c) 2006-2007 Bernhard Reutner-Fischer
5 *
6 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
7 */
8#include <sched.h>
9#include "libbb.h"
10#ifndef _POSIX_PRIORITY_SCHEDULING
11#warning your system may be foobared
12#endif
13
14static const struct {
15	int policy;
16	char name[sizeof("SCHED_OTHER")];
17} policies[] = {
18	{SCHED_OTHER, "SCHED_OTHER"},
19	{SCHED_FIFO, "SCHED_FIFO"},
20	{SCHED_RR, "SCHED_RR"}
21};
22
23//TODO: add
24// -b, SCHED_BATCH
25// -i, SCHED_IDLE
26
27static void show_min_max(int pol)
28{
29	const char *fmt = "%s min/max priority\t: %u/%u\n";
30	int max, min;
31
32	max = sched_get_priority_max(pol);
33	min = sched_get_priority_min(pol);
34	if ((max|min) < 0)
35		fmt = "%s not supported\n";
36	printf(fmt, policies[pol].name, min, max);
37}
38
39#define OPT_m (1<<0)
40#define OPT_p (1<<1)
41#define OPT_r (1<<2)
42#define OPT_f (1<<3)
43#define OPT_o (1<<4)
44
45int chrt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
46int chrt_main(int argc UNUSED_PARAM, char **argv)
47{
48	pid_t pid = 0;
49	unsigned opt;
50	struct sched_param sp;
51	char *pid_str;
52	char *priority = priority; /* for compiler */
53	const char *current_new;
54	int policy = SCHED_RR;
55
56	/* at least 1 arg; only one policy accepted */
57	opt_complementary = "-1:r--fo:f--ro:r--fo";
58	opt = getopt32(argv, "+mprfo");
59	if (opt & OPT_r)
60		policy = SCHED_RR;
61	if (opt & OPT_f)
62		policy = SCHED_FIFO;
63	if (opt & OPT_o)
64		policy = SCHED_OTHER;
65	if (opt & OPT_m) { /* print min/max */
66		show_min_max(SCHED_FIFO);
67		show_min_max(SCHED_RR);
68		show_min_max(SCHED_OTHER);
69		fflush_stdout_and_exit(EXIT_SUCCESS);
70	}
71
72	argv += optind;
73	if (opt & OPT_p) {
74		pid_str = *argv++;
75		if (*argv) { /* "-p <priority> <pid> [...]" */
76			priority = pid_str;
77			pid_str = *argv;
78		}
79		/* else "-p <pid>", and *argv == NULL */
80		pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
81	} else {
82		priority = *argv++;
83		if (!*argv)
84			bb_show_usage();
85	}
86
87	current_new = "current\0new";
88	if (opt & OPT_p) {
89		int pol;
90 print_rt_info:
91		pol = sched_getscheduler(pid);
92		if (pol < 0)
93			bb_perror_msg_and_die("can't %cet pid %d's policy", 'g', pid);
94		printf("pid %d's %s scheduling policy: %s\n",
95				pid, current_new, policies[pol].name);
96		if (sched_getparam(pid, &sp))
97			bb_perror_msg_and_die("can't get pid %d's attributes", pid);
98		printf("pid %d's %s scheduling priority: %d\n",
99				pid, current_new, sp.sched_priority);
100		if (!*argv) {
101			/* Either it was just "-p <pid>",
102			 * or it was "-p <priority> <pid>" and we came here
103			 * for the second time (see goto below) */
104			return EXIT_SUCCESS;
105		}
106		*argv = NULL;
107		current_new += 8;
108	}
109
110	/* from the manpage of sched_getscheduler:
111	[...] sched_priority can have a value in the range 0 to 99.
112	[...] SCHED_OTHER or SCHED_BATCH must be assigned static priority 0.
113	[...] SCHED_FIFO or SCHED_RR can have static priority in 1..99 range.
114	*/
115	sp.sched_priority = xstrtou_range(priority, 0, policy != SCHED_OTHER ? 1 : 0, 99);
116
117	if (sched_setscheduler(pid, policy, &sp) < 0)
118		bb_perror_msg_and_die("can't %cet pid %d's policy", 's', pid);
119
120	if (!argv[0]) /* "-p <priority> <pid> [...]" */
121		goto print_rt_info;
122
123	BB_EXECVP_or_die(argv);
124}
125