miscutils/taskset.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * taskset - retrieve or set a processes' CPU affinity
   4  * Copyright (c) 2006 Bernhard Reutner-Fischer
   5  *
   6  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   7  */
   8
   9 //usage:#define taskset_trivial_usage
  10 //usage:       "[-p] [MASK] [PID | PROG ARGS]"
  11 //usage:#define taskset_full_usage "\n\n"
  12 //usage:       "Set or get CPU affinity\n"
  13 //usage:     "\n        -p      Operate on an existing PID"
  14 //usage:
  15 //usage:#define taskset_example_usage
  16 //usage:       "$ taskset 0x7 ./dgemm_test&\n"
  17 //usage:       "$ taskset -p 0x1 $!\n"
  18 //usage:       "pid 4790's current affinity mask: 7\n"
  19 //usage:       "pid 4790's new affinity mask: 1\n"
  20 //usage:       "$ taskset 0x7 /bin/sh -c './taskset -p 0x1 $$'\n"
  21 //usage:       "pid 6671's current affinity mask: 1\n"
  22 //usage:       "pid 6671's new affinity mask: 1\n"
  23 //usage:       "$ taskset -p 1\n"
  24 //usage:       "pid 1's current affinity mask: 3\n"
  25
  26 #include <sched.h>
  27 #include "libbb.h"
  28
  29 #if ENABLE_FEATURE_TASKSET_FANCY
  30 #define TASKSET_PRINTF_MASK "%s"
  31 /* craft a string from the mask */
  32 static char *from_cpuset(cpu_set_t *mask)
  33 {
  34         int i;
  35         char *ret = NULL;
  36         char *str = xzalloc((CPU_SETSIZE / 4) + 1); /* we will leak it */
  37
  38         for (i = CPU_SETSIZE - 4; i >= 0; i -= 4) {
  39                 int val = 0;
  40                 int off;
  41                 for (off = 0; off <= 3; ++off)
  42                         if (CPU_ISSET(i + off, mask))
  43                                 val |= 1 << off;
  44                 if (!ret && val)
  45                         ret = str;
  46                 *str++ = bb_hexdigits_upcase[val] | 0x20;
  47         }
  48         return ret;
  49 }
  50 #else
  51 #define TASKSET_PRINTF_MASK "%llx"
  52 static unsigned long long from_cpuset(cpu_set_t *mask)
  53 {
  54         struct BUG_CPU_SETSIZE_is_too_small {
  55                 char BUG_CPU_SETSIZE_is_too_small[
  56                         CPU_SETSIZE < sizeof(int) ? -1 : 1];
  57         };
  58         char *p = (void*)mask;
  59
  60         /* Take the least significant bits. Careful!
  61          * Consider both CPU_SETSIZE=4 and CPU_SETSIZE=1024 cases
  62          */
  63 #if BB_BIG_ENDIAN
  64         /* For big endian, it means LAST bits */
  65         if (CPU_SETSIZE < sizeof(long))
  66                 p += CPU_SETSIZE - sizeof(int);
  67         else if (CPU_SETSIZE < sizeof(long long))
  68                 p += CPU_SETSIZE - sizeof(long);
  69         else
  70                 p += CPU_SETSIZE - sizeof(long long);
  71 #endif
  72         if (CPU_SETSIZE < sizeof(long))
  73                 return *(unsigned*)p;
  74         if (CPU_SETSIZE < sizeof(long long))
  75                 return *(unsigned long*)p;
  76         return *(unsigned long long*)p;
  77 }
  78 #endif
  79
  80
  81 int taskset_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  82 int taskset_main(int argc UNUSED_PARAM, char **argv)
  83 {
  84         cpu_set_t mask;
  85         pid_t pid = 0;
  86         unsigned opt_p;
  87         const char *current_new;
  88         char *pid_str;
  89         char *aff = aff; /* for compiler */
  90
  91         /* NB: we mimic util-linux's taskset: -p does not take
  92          * an argument, i.e., "-pN" is NOT valid, only "-p N"!
  93          * Indeed, util-linux-2.13-pre7 uses:
  94          * getopt_long(argc, argv, "+pchV", ...), not "...p:..." */
  95
  96         opt_complementary = "-1"; /* at least 1 arg */
  97         opt_p = getopt32(argv, "+p");
  98         argv += optind;
  99
 100         if (opt_p) {
 101                 pid_str = *argv++;
 102                 if (*argv) { /* "-p <aff> <pid> ...rest.is.ignored..." */
 103                         aff = pid_str;
 104                         pid_str = *argv; /* NB: *argv != NULL in this case */
 105                 }
 106                 /* else it was just "-p <pid>", and *argv == NULL */
 107                 pid = xatoul_range(pid_str, 1, ((unsigned)(pid_t)ULONG_MAX) >> 1);
 108         } else {
 109                 aff = *argv++; /* <aff> <cmd...> */
 110                 if (!*argv)
 111                         bb_show_usage();
 112         }
 113
 114         current_new = "current\0new";
 115         if (opt_p) {
 116  print_aff:
 117                 if (sched_getaffinity(pid, sizeof(mask), &mask) < 0)
 118                         bb_perror_msg_and_die("can't %cet pid %d's affinity", 'g', pid);
 119                 printf("pid %d's %s affinity mask: "TASKSET_PRINTF_MASK"\n",
 120                                 pid, current_new, from_cpuset(&mask));
 121                 if (!*argv) {
 122                         /* Either it was just "-p <pid>",
 123                          * or it was "-p <aff> <pid>" and we came here
 124                          * for the second time (see goto below) */
 125                         return EXIT_SUCCESS;
 126                 }
 127                 *argv = NULL;
 128                 current_new += 8; /* "new" */
 129         }
 130
 131         { /* Affinity was specified, translate it into cpu_set_t */
 132                 unsigned i;
 133                 /* Do not allow zero mask: */
 134                 unsigned long long m = xstrtoull_range(aff, 0, 1, ULLONG_MAX);
 135                 enum { CNT_BIT = CPU_SETSIZE < sizeof(m)*8 ? CPU_SETSIZE : sizeof(m)*8 };
 136
 137                 CPU_ZERO(&mask);
 138                 for (i = 0; i < CNT_BIT; i++) {
 139                         unsigned long long bit = (1ULL << i);
 140                         if (bit & m)
 141                                 CPU_SET(i, &mask);
 142                 }
 143         }
 144
 145         /* Set pid's or our own (pid==0) affinity */
 146         if (sched_setaffinity(pid, sizeof(mask), &mask))
 147                 bb_perror_msg_and_die("can't %cet pid %d's affinity", 's', pid);
 148
 149         if (!argv[0]) /* "-p <aff> <pid> [...ignored...]" */
 150                 goto print_aff; /* print new affinity and exit */
 151
 152         BB_EXECVP_or_die(argv);
 153 }