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/* vi: set sw=4 ts=4: */
/*
* chrt - manipulate real-time attributes of a process
* Copyright (c) 2006-2007 Bernhard Reutner-Fischer
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config CHRT
//config: bool "chrt (4.7 kb)"
//config: default y
//config: help
//config: Manipulate real-time attributes of a process.
//config: This requires sched_{g,s}etparam support in your libc.
//applet:IF_CHRT(APPLET_NOEXEC(chrt, chrt, BB_DIR_USR_BIN, BB_SUID_DROP, chrt))
//kbuild:lib-$(CONFIG_CHRT) += chrt.o
//usage:#define chrt_trivial_usage
//usage: "-m | -p [PRIO] PID | [-rfobi] PRIO PROG ARGS"
//usage:#define chrt_full_usage "\n\n"
//usage: "Change scheduling priority and class for a process\n"
//usage: "\n -m Show min/max priorities"
//usage: "\n -p Operate on PID"
//usage: "\n -r Set SCHED_RR class"
//usage: "\n -f Set SCHED_FIFO class"
//usage: "\n -o Set SCHED_OTHER class"
//usage: "\n -b Set SCHED_BATCH class"
//usage: "\n -i Set SCHED_IDLE class"
//usage:
//usage:#define chrt_example_usage
//usage: "$ chrt -r 4 sleep 900; x=$!\n"
//usage: "$ chrt -f -p 3 $x\n"
//usage: "You need CAP_SYS_NICE privileges to set scheduling attributes of a process"
#include <sched.h>
#include "libbb.h"
#ifndef SCHED_IDLE
# define SCHED_IDLE 5
#endif
//musl has no __MUSL__ or similar define to check for,
//but its <sys/types.h> has these lines:
// #define __NEED_fsblkcnt_t
// #define __NEED_fsfilcnt_t
#if defined(__linux__) && defined(__NEED_fsblkcnt_t) && defined(__NEED_fsfilcnt_t)
# define LIBC_IS_MUSL 1
# include <sys/syscall.h>
#else
# define LIBC_IS_MUSL 0
#endif
static const char *policy_name(int pol)
{
if (pol > 6)
return utoa(pol);
return nth_string(
"OTHER" "\0" /* 0:SCHED_OTHER */
"FIFO" "\0" /* 1:SCHED_FIFO */
"RR" "\0" /* 2:SCHED_RR */
"BATCH" "\0" /* 3:SCHED_BATCH */
"ISO" "\0" /* 4:SCHED_ISO */
"IDLE" "\0" /* 5:SCHED_IDLE */
"DEADLINE", /* 6:SCHED_DEADLINE */
pol
);
}
static void show_min_max(int pol)
{
const char *fmt = "SCHED_%s min/max priority\t: %u/%u\n";
int max, min;
max = sched_get_priority_max(pol);
min = sched_get_priority_min(pol);
if ((max|min) < 0)
fmt = "SCHED_%s not supported\n";
printf(fmt, policy_name(pol), min, max);
}
#define OPT_m (1<<0)
#define OPT_p (1<<1)
#define OPT_r (1<<2)
#define OPT_f (1<<3)
#define OPT_o (1<<4)
#define OPT_b (1<<5)
#define OPT_i (1<<6)
int chrt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int chrt_main(int argc UNUSED_PARAM, char **argv)
{
pid_t pid = 0;
unsigned opt;
struct sched_param sp;
char *pid_str;
char *priority = NULL;
const char *current_new;
int policy = SCHED_RR;
int ret;
opt = getopt32(argv, "^"
"+" "mprfobi"
"\0"
/* only one policy accepted: */
"r--fobi:f--robi:o--rfbi:b--rfoi:i--rfob"
);
if (opt & OPT_m) { /* print min/max and exit */
show_min_max(SCHED_OTHER);
show_min_max(SCHED_FIFO);
show_min_max(SCHED_RR);
show_min_max(SCHED_BATCH);
show_min_max(SCHED_IDLE);
fflush_stdout_and_exit(EXIT_SUCCESS);
}
//if (opt & OPT_r)
// policy = SCHED_RR; - default, already set
if (opt & OPT_f)
policy = SCHED_FIFO;
if (opt & OPT_o)
policy = SCHED_OTHER;
if (opt & OPT_b)
policy = SCHED_BATCH;
if (opt & OPT_i)
policy = SCHED_IDLE;
argv += optind;
if (!argv[0])
bb_show_usage();
if (opt & OPT_p) {
pid_str = *argv++;
if (*argv) { /* "-p PRIO PID [...]" */
priority = pid_str;
pid_str = *argv;
}
/* else "-p PID", and *argv == NULL */
pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
} else {
priority = *argv++;
if (!*argv)
bb_show_usage();
}
current_new = "current\0new";
if (opt & OPT_p) {
int pol;
print_rt_info:
#if LIBC_IS_MUSL
/* musl libc returns ENOSYS for its sched_getscheduler library
* function, because the sched_getscheduler Linux kernel system call
* does not conform to Posix; so we use the system call directly
*/
pol = syscall(SYS_sched_getscheduler, pid);
#else
pol = sched_getscheduler(pid);
#endif
if (pol < 0)
bb_perror_msg_and_die("can't %cet pid %u's policy", 'g', (int)pid);
#ifdef SCHED_RESET_ON_FORK
/* "Since Linux 2.6.32, the SCHED_RESET_ON_FORK flag
* can be ORed in policy when calling sched_setscheduler().
* As a result of including this flag, children created by
* fork(2) do not inherit privileged scheduling policies"
*
* This bit is also returned by sched_getscheduler()!
* (TODO: do we want to show it?)
*/
pol &= ~SCHED_RESET_ON_FORK;
#endif
printf("pid %u's %s scheduling policy: SCHED_%s\n",
pid, current_new, policy_name(pol)
);
#if LIBC_IS_MUSL
ret = syscall(SYS_sched_getparam, pid, &sp);
#else
ret = sched_getparam(pid, &sp);
#endif
if (ret)
bb_perror_msg_and_die("can't get pid %u's attributes", (int)pid);
printf("pid %u's %s scheduling priority: %d\n",
(int)pid, current_new, sp.sched_priority
);
if (!*argv) {
/* Either it was just "-p PID",
* or it was "-p PRIO PID" and we came here
* for the second time (see goto below) */
return EXIT_SUCCESS;
}
*argv = NULL;
current_new += 8;
}
sp.sched_priority = xstrtou_range(priority, 0,
sched_get_priority_min(policy), sched_get_priority_max(policy)
);
#if LIBC_IS_MUSL
ret = syscall(SYS_sched_setscheduler, pid, policy, &sp);
#else
ret = sched_setscheduler(pid, policy, &sp);
#endif
if (ret)
bb_perror_msg_and_die("can't %cet pid %u's policy", 's', (int)pid);
if (!argv[0]) /* "-p PRIO PID [...]" */
goto print_rt_info;
BB_EXECVP_or_die(argv);
}
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