LXR toybox/toys/other/chrt.c

   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
   7USE_CHRT(NEWTOY(chrt, "^mp#<0iRbrfo[!ibrfo]", TOYFLAG_USR|TOYFLAG_BIN))
   8
   9config 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
  30GLOBALS(
  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
  51char *polnames[] = {
  52  "SCHED_OTHER", "SCHED_FIFO", "SCHED_RR", "SCHED_BATCH", 0, "SCHED_IDLE",
  53  "SCHED_DEADLINE"
  54};
  55
  56void 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