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 #define sched_get_priority_min(policy) \
39 (int)syscall(SYS_sched_get_priority_min, (int)policy)
40 #define sched_get_priority_max(policy) \
41 (int)syscall(SYS_sched_get_priority_max, (int)policy)
42 #define sched_getparam(pid, param) \
43 syscall(SYS_sched_getparam, (pid_t)pid, (void *)param)
44 #define sched_getscheduler(pid) \
45 syscall(SYS_sched_getscheduler, (pid_t)pid)
46 #define sched_setscheduler(pid, scheduler, param) \
47 syscall(SYS_sched_setscheduler, (pid_t)pid, (int)scheduler, (void *)param)
48 #endif
49
50 static char *polnames[] = {
51 "SCHED_OTHER", "SCHED_FIFO", "SCHED_RR", "SCHED_BATCH", 0, "SCHED_IDLE",
52 "SCHED_DEADLINE"
53 };
54
chrt_main(void)55 void chrt_main(void)
56 {
57 int pol, pri;
58
59 // Show min/maxes?
60 if (FLAG(m)) {
61 for (pol = 0; pol<ARRAY_LEN(polnames); pol++) if (polnames[pol])
62 printf("%s min/max priority\t: %d/%d\n", polnames[pol],
63 sched_get_priority_min(pol), sched_get_priority_max(pol));
64
65 return;
66 }
67
68 // Query when -p without priority.
69 if (toys.optflags==FLAG_p && !*toys.optargs) {
70 char *s = "???", *R = "";
71
72 if (-1==(pol = sched_getscheduler(TT.p))) perror_exit("pid %ld", TT.p);
73 if (pol & SCHED_RESET_ON_FORK) R = "|SCHED_RESET_ON_FORK";
74 if ((pol &= ~SCHED_RESET_ON_FORK)<ARRAY_LEN(polnames)) s = polnames[pol];
75 printf("pid %ld's current scheduling policy: %s%s\n", TT.p, s, R);
76
77 if (sched_getparam(TT.p, (void *)&pri)) perror_exit("sched_getparam");
78 printf("pid %ld's current scheduling priority: %d\n", TT.p, pri);
79
80 return;
81 }
82
83 if (!*toys.optargs) help_exit("no PRIORITY");
84 if (!toys.optargs[1] == !FLAG(p)) help_exit("need 1 of -p or COMMAND");
85
86 // Set policy and priority
87 if (-1==(pol = highest_bit(toys.optflags&(FLAG_p-1)))) pol = SCHED_RR;
88 pri = atolx_range(*toys.optargs, sched_get_priority_min(pol),
89 sched_get_priority_max(pol));
90 if (FLAG(R)) pol |= SCHED_RESET_ON_FORK;
91
92 if (sched_setscheduler(TT.p, pol, (void *)&pri))
93 perror_exit("sched_setscheduler");
94
95 if (*(toys.optargs+1)) xexec(toys.optargs+1);
96 }
97