1 /* chrt.c - Get/set real-time (scheduling) attributes
2 *
3 * Copyright 2016 The Android Open Source Project
4 *
5 * Note: -ibrfo flags sorted to match SCHED positions for highest_bit()
6
7 USE_CHRT(NEWTOY(chrt, "^mp#<0iRbrfo[!ibrfo]", TOYFLAG_USR|TOYFLAG_BIN))
8
9 config CHRT
10 bool "chrt"
11 default y
12 help
13 usage: chrt [-Rmofrbi] {-p PID [PRIORITY] | [PRIORITY COMMAND...]}
14
15 Get/set a process' real-time scheduling policy and priority.
16
17 -p Set/query given pid (instead of running COMMAND)
18 -R Set SCHED_RESET_ON_FORK
19 -m Show min/max priorities available
20
21 Set policy (default -r):
22
23 -o SCHED_OTHER -f SCHED_FIFO -r SCHED_RR
24 -b SCHED_BATCH -i SCHED_IDLE
25 */
26
27 #define FOR_chrt
28 #include "toys.h"
29
30 GLOBALS(
31 long p;
32 )
33
34 #ifndef _POSIX_PRIORITY_SCHEDULING
35 // musl-libc intentionally broke sched_get_priority_min() and friends in
36 // commit 1e21e78bf7a5 because its maintainer didn't like those Linux
37 // system calls, so work around it here.
38 #include <sys/syscall.h>
39 #define sched_get_priority_min(policy) \
40 (int)syscall(SYS_sched_get_priority_min, (int)policy)
41 #define sched_get_priority_max(policy) \
42 (int)syscall(SYS_sched_get_priority_max, (int)policy)
43 #define sched_getparam(pid, param) \
44 syscall(SYS_sched_getparam, (pid_t)pid, (void *)param)
45 #define sched_getscheduler(pid) \
46 syscall(SYS_sched_getscheduler, (pid_t)pid)
47 #define sched_setscheduler(pid, scheduler, param) \
48 syscall(SYS_sched_setscheduler, (pid_t)pid, (int)scheduler, (void *)param)
49 #endif
50
51 char *polnames[] = {
52 "SCHED_OTHER", "SCHED_FIFO", "SCHED_RR", "SCHED_BATCH", 0, "SCHED_IDLE",
53 "SCHED_DEADLINE"
54 };
55
chrt_main(void)56 void chrt_main(void)
57 {
58 int pol, pri;
59
60 // Show min/maxes?
61 if (toys.optflags&FLAG_m) {
62 for (pol = 0; pol<ARRAY_LEN(polnames); pol++) if (polnames[pol])
63 printf("%s min/max priority\t: %d/%d\n", polnames[pol],
64 sched_get_priority_min(pol), sched_get_priority_max(pol));
65
66 return;
67 }
68
69 // Query when -p without priority.
70 if (toys.optflags==FLAG_p && !*toys.optargs) {
71 char *s = "???", *R = "";
72
73 if (-1==(pol = sched_getscheduler(TT.p))) perror_exit("pid %ld", TT.p);
74 if (pol & SCHED_RESET_ON_FORK) R = "|SCHED_RESET_ON_FORK";
75 if ((pol &= ~SCHED_RESET_ON_FORK)<ARRAY_LEN(polnames)) s = polnames[pol];
76 printf("pid %ld's current scheduling policy: %s%s\n", TT.p, s, R);
77
78 if (sched_getparam(TT.p, (void *)&pri)) perror_exit("sched_getparam");
79 printf("pid %ld's current scheduling priority: %d\n", TT.p, pri);
80
81 return;
82 }
83
84 if (!*toys.optargs) help_exit("no PRIORITY");
85 if (!toys.optargs[1] == !(toys.optflags&FLAG_p))
86 help_exit("need 1 of -p or COMMAND");
87
88 // Set policy and priority
89 if (-1==(pol = highest_bit(toys.optflags&0x2f))) pol = SCHED_RR;
90 pri = atolx_range(*toys.optargs, sched_get_priority_min(pol),
91 sched_get_priority_max(pol));
92 if (toys.optflags&FLAG_R) pol |= SCHED_RESET_ON_FORK;
93
94 if (sched_setscheduler(TT.p, pol, (void *)&pri))
95 perror_exit("sched_setscheduler");
96
97 if (*(toys.optargs+1)) xexec(toys.optargs+1);
98 }
99