sigstep.c

这个是LINUX下的GDB调度工具的源码

/* This testcase is part of GDB, the GNU debugger.

   Copyright 2004 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

*/

#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/time.h>

static volatile int done;

static void
handler (int sig)
{
  done = 1;
} /* handler */

struct itimerval itime;
struct sigaction action;

/* The enum is so that GDB can easily see these macro values.  */
enum {
  itimer_real = ITIMER_REAL,
  itimer_virtual = ITIMER_VIRTUAL
} itimer = ITIMER_VIRTUAL;

main ()
{

  /* Set up the signal handler.  */
  memset (&action, 0, sizeof (action));
  action.sa_handler = handler;
  sigaction (SIGVTALRM, &action, NULL);
  sigaction (SIGALRM, &action, NULL);

  /* The values needed for the itimer.  This needs to be at least long
     enough for the setitimer() call to return.  */
  memset (&itime, 0, sizeof (itime));
  itime.it_value.tv_usec = 250 * 1000;

  /* Loop for ever, constantly taking an interrupt.  */
  while (1)
    {
      /* Set up a one-off timer.  A timer, rather than SIGSEGV, is
	 used as after a timer handler finishes the interrupted code
	 can safely resume.  */
      setitimer (itimer, &itime, NULL);
      /* Wait.  */
      while (!done);
      done = 0;
    }
}