Attachment 263751 Details for Bug 159663 – Comment 1 attachment fixed up.

Comment 1 attachment fixed up.

bz159663.c (text/plain), 4.02 KB, created by Jan Kratochvil on 2007-11-19 18:09:48 UTC

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Creator: Jan Kratochvil

Created: 2007-11-19 18:09:48 UTC

Size: 4.02 KB

patch

obsolete

>#include <sys/types.h>
>#include <unistd.h>
>#include <pthread.h>
>#include <stdlib.h>
>#include <sys/ptrace.h>
>#include <dirent.h>
>#include <stdio.h>
>#include <signal.h>
>#include <errno.h>
>#include <sys/wait.h>
>#include <sys/poll.h>
>#include <assert.h>
>#include <string.h>
>
>#include <asm/unistd.h>
>#include <unistd.h>
>#define tkill(tid, sig) syscall (__NR_tkill, (tid), (sig))
>
>struct lwp_stop {
>  int lwpid;
>  int num_stops;
>};
>
>struct lwp_stop lwp[3];
>
>static
>void *infLoopThreadFunc (void *args)
>{
>  for (;;)
>    ;
>  return NULL;
>}
>
>static 
>int infThreadLoop (int n)
>{
>  int i = 0;
>  pid_t pid = fork ();
>  if (pid == 0) {
>    // want child to create n threads performing an infinite loop
>    pthread_t p[1000];  // up to 1000 threads
>    for (i = 0; i < n; ++i) {
>      pthread_create (&p[i], NULL, &infLoopThreadFunc, NULL);
>    }
>
>    for (i = 0; i < n; ++i)
>      pthread_join (p[i], NULL);
>
>    exit (0);
>  }
>  sleep (1);
>  return (int)pid;
>}   
>
>static void
>wait_stop (pid_t pid, int do_continue)
>{
>  {
>    pid_t pid_got;
>    int status;
>    int i;
>    long l;
>    errno = 0;
>
>    // Keep fetching the wait status until there are none left.
>    /* WNOHANG is racy, never use it.  */
>    pid_got = waitpid (pid, &status, __WALL);
>    assert (pid_got == pid);
>    assert (WIFSTOPPED (status));
>    {
>      printf ("stop event %d on <%d>\n", WSTOPSIG (status), (int) pid);
>      /* There may have been already enqueued signal before PTRACE_ATTACH or
>         our other signal sent.  Redeliver it and read the next signal in the
>         queue.  */
>      if (WSTOPSIG (status) != SIGSTOP) {
>	l = ptrace (PTRACE_CONT, pid, NULL, (void *) (long) WSTOPSIG (status));
>	assert (l == 0);
>	/* Try again.  */
>	wait_stop (pid, do_continue);
>	return;
>	}
>      for (i = 0; i < 3; ++i)
>        if (lwp[i].lwpid == pid)
>          break;
>      assert (i < 3);
>      if (lwp[i].num_stops++ == 0) {
>	printf ("continuing first stop\n");
>        l = ptrace (PTRACE_CONT, pid, NULL, 0);
>	assert (l == 0);
>      }
>    }
>  }
>}
>
>int main ()
>{
>   char buf [40];
>   DIR *dir;
>   struct dirent *d;
>   int lwpid;
>   int i;
>   int pid = infThreadLoop (2);
>   long l;
>
>   /* Wait until all the child threads get spawned.  It is racy here, we should
>      check the number of threads in READDIR below.  */
>   sleep (1);
>
>   lwp[0].lwpid = pid;
>
>   /* Attach to new pid and the two threads */
>   printf ("Attaching %d\n", pid);
>   l = ptrace (PTRACE_ATTACH, pid, 0, 0);
>   assert (l == 0);
>
>   wait_stop (pid, 1);
>
>   sprintf (buf, "/proc/%d/task/", pid);
>
>   dir = opendir (buf);
>
>   /* Skip over . and .. */
>   d = readdir (dir);
>   assert (strcmp (d->d_name, ".") == 0);
>   d = readdir (dir);
>   assert (strcmp (d->d_name, "..") == 0);
>
>   for (i = 0; i < 3; ++i) {
>     d = readdir (dir);
>     lwpid = atoi (d->d_name);
>     printf ("lwpid is %d\n", lwpid);
>     if (lwpid != pid) {
>       if (lwp[1].lwpid == 0)
>         lwp[1].lwpid = lwpid;
>       else if (lwp[2].lwpid == 0)
>         lwp[2].lwpid = lwpid;
>       else
>         assert (0);
>       printf ("Attaching %d\n", lwpid);
>       errno = 0;
>       ptrace (PTRACE_ATTACH, lwpid, 0, 0);
>       if (errno != 0)
>         perror ("attach lwpid");
>       wait_stop (lwpid, 1);
>     }
>   }
>
>   printf ("About to kill main thread\n");
>
>   /* Now try manually stopping threads.  */
>   /* kill (pid, SIGSTOP) here would:
>      * Try to deliver SIGSTOP to an arbitrary task of those three.
>      * Just get into `State: T (tracing stop)' and WAITPID back with `WSTOPSIG
>        (status) == SIGSTOP' for that arbitrarily chosen task.
>      Process under ptrace(2) no longer stops completely by a single SIGSTOP,
>      under ptrace(2) SIGSTOP applies only to a single task of the process
>      group.  */
>   
>   i = tkill (pid, SIGSTOP);
>   assert (i == 0);
>   wait_stop (pid, 0);
>   
>   i = tkill (lwp[1].lwpid, SIGSTOP);
>   assert (i == 0);
>   wait_stop (lwp[1].lwpid, 0);
>   
>   i = tkill (lwp[2].lwpid, SIGSTOP);
>   assert (i == 0);
>   wait_stop (lwp[2].lwpid, 0);
> 
>   printf ("Manually check to see what threads are stopped.\n");
>
>   pause ();
>
>   closedir (dir);
>
>   return EXIT_SUCCESS;
>}

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Attachments on bug 159663: 115173 | 263751