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taskset.c

/*
 * taskset.c - taskset
 * Command-line utility for setting and retrieving a task's CPU affinity
 *
 * Robert Love <rml@tech9.net>            25 April 2002
 *
 * Linux kernels as of 2.5.8 provide the needed syscalls for
 * working with a task's cpu affinity.  Currently 2.4 does not
 * support these syscalls, but patches are available at:
 *
 *    http://www.kernel.org/pub/linux/kernel/people/rml/cpu-affinity/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, v2, as
 * published by the Free Software Foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Copyright (C) 2004 Robert Love
 */

#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <getopt.h>
#include <sched.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>

static void show_usage(const char *cmd)
{
      fprintf(stderr, "taskset version " VERSION "\n");
      fprintf(stderr, "usage: %s [options] [mask | cpu-list] [pid |"\
            " cmd [args...]]\n", cmd);
      fprintf(stderr, "set or get the affinity of a process\n\n");
      fprintf(stderr, "  -p, --pid                  "
            "operate on existing given pid\n");
        fprintf(stderr, "  -c, --cpu-list             "\
            "display and specify cpus in list format\n");
      fprintf(stderr, "  -h, --help                 display this help\n");
      fprintf(stderr, "  -v, --version              "\
            "output version information\n\n");
      fprintf(stderr, "The default behavior is to run a new command:\n");
      fprintf(stderr, "  %s 03 sshd -b 1024\n", cmd);
      fprintf(stderr, "You can retrieve the mask of an existing task:\n");
      fprintf(stderr, "  %s -p 700\n", cmd);
      fprintf(stderr, "Or set it:\n");
      fprintf(stderr, "  %s -p 03 700\n", cmd);
      fprintf(stderr, "List format uses a comma-separated list instead"\
                  " of a mask:\n");
      fprintf(stderr, "  %s -pc 0,3,7-11 700\n", cmd);
      fprintf(stderr, "Ranges in list format can take a stride argument:\n");
      fprintf(stderr, "  e.g. 0-31:2 is equivalent to mask 0x55555555\n\n");
}

static inline int val_to_char(int v)
{
      if (v >= 0 && v < 10)
            return '0' + v;
      else if (v >= 10 && v < 16)
            return ('a' - 10) + v;
      else 
            return -1;
}

static char * cpuset_to_str(cpu_set_t *mask, char *str)
{
      int base;
      char *ptr = str;
      char *ret = 0;

      for (base = CPU_SETSIZE - 4; base >= 0; base -= 4) {
            char val = 0;
            if (CPU_ISSET(base, mask))
                  val |= 1;
            if (CPU_ISSET(base + 1, mask))
                  val |= 2;
            if (CPU_ISSET(base + 2, mask))
                  val |= 4;
            if (CPU_ISSET(base + 3, mask))
                  val |= 8;
            if (!ret && val)
                  ret = ptr;
            *ptr++ = val_to_char(val);
      }
      *ptr = 0;
      return ret ? ret : ptr - 1;
}

static char * cpuset_to_cstr(cpu_set_t *mask, char *str)
{
      int i;
      char *ptr = str;
      int entry_made = 0;

      for (i = 0; i < CPU_SETSIZE; i++) {
            if (CPU_ISSET(i, mask)) {
                  int j;
                  int run = 0;
                  entry_made = 1;
                  for (j = i + 1; j < CPU_SETSIZE; j++) {
                        if (CPU_ISSET(j, mask))
                              run++;
                        else
                              break;
                  }
                  if (!run)
                        sprintf(ptr, "%d,", i);
                  else if (run == 1) {
                        sprintf(ptr, "%d,%d,", i, i + 1);
                        i++;
                  } else {
                        sprintf(ptr, "%d-%d,", i, i + run);
                        i += run;
                  }
                  while (*ptr != 0)
                        ptr++;
            }
      }
      ptr -= entry_made;
      *ptr = 0;

      return str;
}

static inline int char_to_val(int c)
{
      int cl;

      cl = tolower(c);
      if (c >= '0' && c <= '9')
            return c - '0';
      else if (cl >= 'a' && cl <= 'f')
            return cl + (10 - 'a');
      else
            return -1;
}

static int str_to_cpuset(cpu_set_t *mask, const char* str)
{
      int len = strlen(str);
      const char *ptr = str + len - 1;
      int base = 0;

      /* skip 0x, it's all hex anyway */
      if (len > 1 && !memcmp(str, "0x", 2L))
            str += 2;

      CPU_ZERO(mask);
      while (ptr >= str) {
            char val = char_to_val(*ptr);
            if (val == (char) -1)
                  return -1;
            if (val & 1)
                  CPU_SET(base, mask);
            if (val & 2)
                  CPU_SET(base + 1, mask);
            if (val & 4)
                  CPU_SET(base + 2, mask);
            if (val & 8)
                  CPU_SET(base + 3, mask);
            len--;
            ptr--;
            base += 4;
      }

      return 0;
}

static const char *nexttoken(const char *q,  int sep)
{
      if (q)
            q = strchr(q, sep);
      if (q)
            q++;
      return q;
}

static int cstr_to_cpuset(cpu_set_t *mask, const char* str)
{
      const char *p, *q;
      q = str;
      CPU_ZERO(mask);

      while (p = q, q = nexttoken(q, ','), p) {
            unsigned int a;   /* beginning of range */
            unsigned int b;   /* end of range */
            unsigned int s;   /* stride */
            const char *c1, *c2;

            if (sscanf(p, "%u", &a) < 1)
                  return 1;
            b = a;
            s = 1;

            c1 = nexttoken(p, '-');
            c2 = nexttoken(p, ',');
            if (c1 != NULL && (c2 == NULL || c1 < c2)) {
                  if (sscanf(c1, "%u", &b) < 1)
                        return 1;
                  c1 = nexttoken(c1, ':');
                  if (c1 != NULL && (c2 == NULL || c1 < c2))
                        if (sscanf(c1, "%u", &s) < 1) {
                              return 1;
                  }
            }

            if (!(a <= b))
                  return 1;
            while (a <= b) {
                  CPU_SET(a, mask);             
                  a += s;
            }
      }

      return 0;
}

int main(int argc, char *argv[])
{
      cpu_set_t new_mask, cur_mask;
      pid_t pid = 0;
      int opt, err;
      char mstr[1 + CPU_SETSIZE / 4];
      char cstr[7 * CPU_SETSIZE];
      int c_opt = 0;

      struct option longopts[] = {
            { "pid",    0, NULL, 'p' },
            { "cpu-list",     0, NULL, 'c' },
            { "help",   0, NULL, 'h' },
            { "version",      0, NULL, 'V' },
            { NULL,           0, NULL, 0 }
      };

      while ((opt = getopt_long(argc, argv, "+pchV", longopts, NULL)) != -1) {
            int ret = 1;

            switch (opt) {
            case 'p':
                  pid = atoi(argv[argc - 1]);
                  break;
            case 'c':
                  c_opt = 1;
                  break;
            case 'V':
                  printf("taskset version " VERSION "\n");
                  return 0;
            case 'h':
                  ret = 0;
            default:
                  show_usage(argv[0]);
                  return ret;
            }
      }

      if ((!pid && argc - optind < 2)
                  || (pid && (argc - optind < 1 || argc - optind > 2))) {
            show_usage(argv[0]);
            return 1;
      }

      if (pid) {
            if (sched_getaffinity(pid, sizeof (cur_mask), &cur_mask) < 0) {
                  perror("sched_getaffinity");
                  fprintf(stderr, "failed to get pid %d's affinity\n",
                        pid);
                  return 1;
            }
            if (c_opt)
                  printf("pid %d's current affinity list: %s\n", pid,
                        cpuset_to_cstr(&cur_mask, cstr));
            else
                  printf("pid %d's current affinity mask: %s\n", pid,
                        cpuset_to_str(&cur_mask, mstr));

            if (argc - optind == 1)
                  return 0;
      }

      if (c_opt)
            err = cstr_to_cpuset(&new_mask, argv[optind]);
      else
            err = str_to_cpuset(&new_mask, argv[optind]);

      if (err) {
            if (c_opt)
                  fprintf(stderr, "failed to parse CPU list %s\n",
                        argv[optind]);
            else
                  fprintf(stderr, "failed to parse CPU mask %s\n",
                        argv[optind]);
            return 1;
      }

      if (sched_setaffinity(pid, sizeof (new_mask), &new_mask)) {
            perror("sched_setaffinity");
            fprintf(stderr, "failed to set pid %d's affinity.\n", pid);
            return 1;
      }

      if (sched_getaffinity(pid, sizeof (cur_mask), &cur_mask) < 0) {
            perror("sched_getaffinity");
            fprintf(stderr, "failed to get pid %d's affinity.\n", pid);
            return 1;
      }

      if (pid) {
            if (c_opt)
                  printf("pid %d's new affinity list: %s\n", pid, 
                           cpuset_to_cstr(&cur_mask, cstr));
            else
                  printf("pid %d's new affinity mask: %s\n", pid, 
                           cpuset_to_str(&cur_mask, mstr));
      } else {
            argv += optind + 1;
            execvp(argv[0], argv);
            perror("execvp");
            fprintf(stderr, "failed to execute %s\n", argv[0]);
            return 1;
      }

      return 0;
}

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