release/src/router/busybox/miscutils/chrt.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * chrt - manipulate real-time attributes of a process
   4  * Copyright (c) 2006-2007 Bernhard Reutner-Fischer
   5  *
   6  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   7  */
   8
   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"
  18 //usage:
  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"
  23
  24 #include <sched.h>
  25 #include "libbb.h"
  26 #ifndef _POSIX_PRIORITY_SCHEDULING
  27 #warning your system may be foobared
  28 #endif
  29
  30 static const struct {
  31         int policy;
  32         char name[sizeof("SCHED_OTHER")];
  33 } policies[] = {
  34         {SCHED_OTHER, "SCHED_OTHER"},
  35         {SCHED_FIFO, "SCHED_FIFO"},
  36         {SCHED_RR, "SCHED_RR"}
  37 };
  38
  39 //TODO: add
  40 // -b, SCHED_BATCH
  41 // -i, SCHED_IDLE
  42
  43 static void show_min_max(int pol)
  44 {
  45         const char *fmt = "%s min/max priority\t: %u/%u\n";
  46         int max, min;
  47
  48         max = sched_get_priority_max(pol);
  49         min = sched_get_priority_min(pol);
  50         if ((max|min) < 0)
  51                 fmt = "%s not supported\n";
  52         printf(fmt, policies[pol].name, min, max);
  53 }
  54
  55 #define OPT_m (1<<0)
  56 #define OPT_p (1<<1)
  57 #define OPT_r (1<<2)
  58 #define OPT_f (1<<3)
  59 #define OPT_o (1<<4)
  60
  61 int chrt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  62 int chrt_main(int argc UNUSED_PARAM, char **argv)
  63 {
  64         pid_t pid = 0;
  65         unsigned opt;
  66         struct sched_param sp;
  67         char *pid_str;
  68         char *priority = priority; /* for compiler */
  69         const char *current_new;
  70         int policy = SCHED_RR;
  71
  72         /* only one policy accepted */
  73         opt_complementary = "r--fo:f--ro:o--rf";
  74         opt = getopt32(argv, "+mprfo");
  75         if (opt & OPT_m) { /* print min/max and exit */
  76                 show_min_max(SCHED_FIFO);
  77                 show_min_max(SCHED_RR);
  78                 show_min_max(SCHED_OTHER);
  79                 fflush_stdout_and_exit(EXIT_SUCCESS);
  80         }
  81         if (opt & OPT_r)
  82                 policy = SCHED_RR;
  83         if (opt & OPT_f)
  84                 policy = SCHED_FIFO;
  85         if (opt & OPT_o)
  86                 policy = SCHED_OTHER;
  87
  88         argv += optind;
  89         if (!argv[0])
  90                 bb_show_usage();
  91         if (opt & OPT_p) {
  92                 pid_str = *argv++;
  93                 if (*argv) { /* "-p <priority> <pid> [...]" */
  94                         priority = pid_str;
  95                         pid_str = *argv;
  96                 }
  97                 /* else "-p <pid>", and *argv == NULL */
  98                 pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
  99         } else {
 100                 priority = *argv++;
 101                 if (!*argv)
 102                         bb_show_usage();
 103         }
 104
 105         current_new = "current\0new";
 106         if (opt & OPT_p) {
 107                 int pol;
 108  print_rt_info:
 109                 pol = sched_getscheduler(pid);
 110                 if (pol < 0)
 111                         bb_perror_msg_and_die("can't %cet pid %d's policy", 'g', (int)pid);
 112                 printf("pid %d's %s scheduling policy: %s\n",
 113                                 pid, current_new, policies[pol].name);
 114                 if (sched_getparam(pid, &sp))
 115                         bb_perror_msg_and_die("can't get pid %d's attributes", (int)pid);
 116                 printf("pid %d's %s scheduling priority: %d\n",
 117                                 (int)pid, current_new, sp.sched_priority);
 118                 if (!*argv) {
 119                         /* Either it was just "-p <pid>",
 120                          * or it was "-p <priority> <pid>" and we came here
 121                          * for the second time (see goto below) */
 122                         return EXIT_SUCCESS;
 123                 }
 124                 *argv = NULL;
 125                 current_new += 8;
 126         }
 127
 128         /* from the manpage of sched_getscheduler:
 129         [...] sched_priority can have a value in the range 0 to 99.
 130         [...] SCHED_OTHER or SCHED_BATCH must be assigned static priority 0.
 131         [...] SCHED_FIFO or SCHED_RR can have static priority in 1..99 range.
 132         */
 133         sp.sched_priority = xstrtou_range(priority, 0, policy != SCHED_OTHER ? 1 : 0, 99);
 134
 135         if (sched_setscheduler(pid, policy, &sp) < 0)
 136                 bb_perror_msg_and_die("can't %cet pid %d's policy", 's', (int)pid);
 137
 138         if (!argv[0]) /* "-p <priority> <pid> [...]" */
 139                 goto print_rt_info;
 140
 141         BB_EXECVP_or_die(argv);
 142 }