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Date: Sun, 1 Feb 2004 18:55:50 -0800 (PST)
From: Davide Libenzi <davidel@xmailserver.org>
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To: Davide Libenzi <davidel@xmailserver.org>
cc: Daniel Jacobowitz <dan@debian.org>, Linus Torvalds <torvalds@osdl.org>,
       Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Roland McGrath <roland@redhat.com>, Ingo Molnar <mingo@elte.hu>
Subject: Re: More waitpid issues with CLONE_DETACHED/CLONE_THREAD
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On Sun, 1 Feb 2004, Davide Libenzi wrote:

> > That may be (though I don't think so) but it reproduces without
> > PTRACE_KILL too.  Try the attached, which just replaced PTRACE_KILL
> > with PTRACE_CONT/tkill(pid, SIGKILL).  Still get zombies.  I haven't
> > tried reproducing entirely without ptrace yet.
> 
> Here w/out ptrace works as advertised.

Yes, even for something that uses tkill() :-)


- Davide




/* -DBUG to kill the parent before the child -> hang.  */
/* -DNOTHREAD to us fork instead of clone.  */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <signal.h>
#include <sched.h>
#include <errno.h>
#include <sys/wait.h>


int stack_one[8192], stack_two[8192];
int fds1[2], fds2[2];


int thread_func_two()
{

	fprintf(stdout, "Thread 2: ppid = %d\n", getppid());
	while (1) {
		sleep (1);
		fprintf(stdout, "Thread 2: ppid = %d\n", getppid());
	}
}

int thread_func_one()
{
	int ret;

	fprintf(stdout, "Thread 1\n");

	read(fds1[0], &ret, sizeof(int));

	fprintf(stdout, "Thread 1 cloning\n");

	ret = clone (thread_func_two, stack_two + 8192,
#ifdef NOTHREAD
		     SIGCHLD,
#else
		     CLONE_DETACHED | CLONE_THREAD | CLONE_SIGHAND | CLONE_VM | CLONE_FS,
#endif
		     NULL);

	fprintf(stdout, "child2 = %d\n", ret);

	write(fds2[1], &ret, sizeof(int));

	fprintf(stdout, "Thread 1 sleeping\n");
	while (1)
		sleep (1);
}

int main()
{
	int ret, wstat, child, child2;

	if (pipe(fds1) < 0 || pipe(fds2)) {
		perror("pipe");
		return 1;
	}

	child = fork();
	if (child == 0)
		return thread_func_one();

	fprintf(stdout, "child = %d\n", child);

	write(fds1[1], &child, sizeof(int));
	read(fds2[0], &child2, sizeof(int));

	fprintf(stdout, "parent got child2 = %d\n", child2);

#ifndef BUG
	syscall(SYS_tkill, child2, SIGKILL);
	ret = waitpid (child2, &wstat, __WALL);
	fprintf(stdout, "waitpid(%d) = %d (%s)\n", child2, ret,
		ret < 0 ? strerror(errno): "Success");
#endif

	syscall(SYS_tkill, child, SIGKILL);
	ret = waitpid (child, &wstat, __WALL);
	fprintf(stdout, "waitpid(%d) = %d (%s)\n", child, ret,
		ret < 0 ? strerror(errno): "Success");

#ifdef BUG
	sleep(2);

	syscall(SYS_tkill, child2, SIGKILL);
	ret = waitpid (child2, &wstat, __WALL);
	fprintf(stdout, "waitpid(%d) = %d (%s)\n", child2, ret,
		ret < 0 ? strerror(errno): "Success");
#endif

	return 0;
}