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.
9 //usage:#define chrt_trivial_usage
10 //usage: "[-prfom] [PRIO] [PID | PROG ARGS]"
11 //usage:#define chrt_full_usage "\n\n"
12 //usage: "Change scheduling priority and class for a process\n"
13 //usage: "\n -p Operate on PID"
14 //usage: "\n -r Set SCHED_RR class"
15 //usage: "\n -f Set SCHED_FIFO class"
16 //usage: "\n -o Set SCHED_OTHER class"
17 //usage: "\n -m Show min/max priorities"
19 //usage:#define chrt_example_usage
20 //usage: "$ chrt -r 4 sleep 900; x=$!\n"
21 //usage: "$ chrt -f -p 3 $x\n"
22 //usage: "You need CAP_SYS_NICE privileges to set scheduling attributes of a process"
29 char name[sizeof("SCHED_OTHER")];
31 {SCHED_OTHER, "SCHED_OTHER"},
32 {SCHED_FIFO, "SCHED_FIFO"},
33 {SCHED_RR, "SCHED_RR"}
40 static void show_min_max(int pol)
42 const char *fmt = "%s min/max priority\t: %u/%u\n";
45 max = sched_get_priority_max(pol);
46 min = sched_get_priority_min(pol);
48 fmt = "%s not supported\n";
49 printf(fmt, policies[pol].name, min, max);
58 int chrt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
59 int chrt_main(int argc UNUSED_PARAM, char **argv)
63 struct sched_param sp;
65 char *priority = priority; /* for compiler */
66 const char *current_new;
67 int policy = SCHED_RR;
69 /* only one policy accepted */
70 opt_complementary = "r--fo:f--ro:o--rf";
71 opt = getopt32(argv, "+mprfo");
72 if (opt & OPT_m) { /* print min/max and exit */
73 show_min_max(SCHED_FIFO);
74 show_min_max(SCHED_RR);
75 show_min_max(SCHED_OTHER);
76 fflush_stdout_and_exit(EXIT_SUCCESS);
90 if (*argv) { /* "-p <priority> <pid> [...]" */
94 /* else "-p <pid>", and *argv == NULL */
95 pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
102 current_new = "current\0new";
106 pol = sched_getscheduler(pid);
108 bb_perror_msg_and_die("can't %cet pid %d's policy", 'g', (int)pid);
109 printf("pid %d's %s scheduling policy: %s\n",
110 pid, current_new, policies[pol].name);
111 if (sched_getparam(pid, &sp))
112 bb_perror_msg_and_die("can't get pid %d's attributes", (int)pid);
113 printf("pid %d's %s scheduling priority: %d\n",
114 (int)pid, current_new, sp.sched_priority);
116 /* Either it was just "-p <pid>",
117 * or it was "-p <priority> <pid>" and we came here
118 * for the second time (see goto below) */
125 /* from the manpage of sched_getscheduler:
126 [...] sched_priority can have a value in the range 0 to 99.
127 [...] SCHED_OTHER or SCHED_BATCH must be assigned static priority 0.
128 [...] SCHED_FIFO or SCHED_RR can have static priority in 1..99 range.
130 sp.sched_priority = xstrtou_range(priority, 0, policy != SCHED_OTHER ? 1 : 0, 99);
132 if (sched_setscheduler(pid, policy, &sp) < 0)
133 bb_perror_msg_and_die("can't %cet pid %d's policy", 's', (int)pid);
135 if (!argv[0]) /* "-p <priority> <pid> [...]" */
138 BB_EXECVP_or_die(argv);