1 /* vi: set sw=4 ts=4: */
3 * chrt - manipulate real-time attributes of a process
4 * Copyright (c) 2006-2007 Bernhard Reutner-Fischer
6 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
12 //config: manipulate real-time attributes of a process.
13 //config: This requires sched_{g,s}etparam support in your libc.
15 //applet:IF_CHRT(APPLET(chrt, BB_DIR_USR_BIN, BB_SUID_DROP))
17 //kbuild:lib-$(CONFIG_CHRT) += chrt.o
19 //usage:#define chrt_trivial_usage
20 //usage: "[-prfom] [PRIO] [PID | PROG ARGS]"
21 //usage:#define chrt_full_usage "\n\n"
22 //usage: "Change scheduling priority and class for a process\n"
23 //usage: "\n -p Operate on PID"
24 //usage: "\n -r Set SCHED_RR class"
25 //usage: "\n -f Set SCHED_FIFO class"
26 //usage: "\n -o Set SCHED_OTHER class"
27 //usage: "\n -m Show min/max priorities"
29 //usage:#define chrt_example_usage
30 //usage: "$ chrt -r 4 sleep 900; x=$!\n"
31 //usage: "$ chrt -f -p 3 $x\n"
32 //usage: "You need CAP_SYS_NICE privileges to set scheduling attributes of a process"
39 char name[sizeof("SCHED_OTHER")];
41 {SCHED_OTHER, "SCHED_OTHER"},
42 {SCHED_FIFO, "SCHED_FIFO"},
43 {SCHED_RR, "SCHED_RR"}
50 static void show_min_max(int pol)
52 const char *fmt = "%s min/max priority\t: %u/%u\n";
55 max = sched_get_priority_max(pol);
56 min = sched_get_priority_min(pol);
58 fmt = "%s not supported\n";
59 printf(fmt, policies[pol].name, min, max);
68 int chrt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
69 int chrt_main(int argc UNUSED_PARAM, char **argv)
73 struct sched_param sp;
75 char *priority = priority; /* for compiler */
76 const char *current_new;
77 int policy = SCHED_RR;
79 /* only one policy accepted */
80 opt_complementary = "r--fo:f--ro:o--rf";
81 opt = getopt32(argv, "+mprfo");
82 if (opt & OPT_m) { /* print min/max and exit */
83 show_min_max(SCHED_FIFO);
84 show_min_max(SCHED_RR);
85 show_min_max(SCHED_OTHER);
86 fflush_stdout_and_exit(EXIT_SUCCESS);
100 if (*argv) { /* "-p <priority> <pid> [...]" */
104 /* else "-p <pid>", and *argv == NULL */
105 pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
112 current_new = "current\0new";
116 pol = sched_getscheduler(pid);
118 bb_perror_msg_and_die("can't %cet pid %d's policy", 'g', (int)pid);
119 printf("pid %d's %s scheduling policy: %s\n",
120 pid, current_new, policies[pol].name);
121 if (sched_getparam(pid, &sp))
122 bb_perror_msg_and_die("can't get pid %d's attributes", (int)pid);
123 printf("pid %d's %s scheduling priority: %d\n",
124 (int)pid, current_new, sp.sched_priority);
126 /* Either it was just "-p <pid>",
127 * or it was "-p <priority> <pid>" and we came here
128 * for the second time (see goto below) */
135 /* from the manpage of sched_getscheduler:
136 [...] sched_priority can have a value in the range 0 to 99.
137 [...] SCHED_OTHER or SCHED_BATCH must be assigned static priority 0.
138 [...] SCHED_FIFO or SCHED_RR can have static priority in 1..99 range.
140 sp.sched_priority = xstrtou_range(priority, 0, policy != SCHED_OTHER ? 1 : 0, 99);
142 if (sched_setscheduler(pid, policy, &sp) < 0)
143 bb_perror_msg_and_die("can't %cet pid %d's policy", 's', (int)pid);
145 if (!argv[0]) /* "-p <priority> <pid> [...]" */
148 BB_EXECVP_or_die(argv);