[PATCH] Re: Zombies with 2.4.15pre5 (exit.c)

From: Dave McCracken (dmccr@us.ibm.com)
Date: Tue Nov 20 2001 - 11:08:12 EST


--On Saturday, November 17, 2001 03:45:49 +0000 Jeff Long
<jeffwlong@hotmail.com> wrote:

> Running 2.4.15pre5 (UP) on i386, running UML 2.4.14-2.
> UML processes create threads on the host system that don't
> die. Threads are stuck at do_exit( ), so I backed out the
> patch to kernel/exit.c @ 539 (in 2.4.15pre5 patch):
>
> p->state = TASK_DEAD;
>
> and things work fine. I do not see zombies with anything
> other than UML processes/native threads.

The intent of the original patch was to make the task unfindable to other
waiters, which fixed a race condition in sys_wait4(). My assumption was
that the task was about to be cleaned up in release_task(). What I missed
was that there are a couple of code paths that don't release the task, but
assume it'll be cleaned up later.

The patch below should fix the problem.

Dave McCracken

======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
dmccr@us.ibm.com T/L 678-3059

-----------------------

--- linux-2.4.15-pre7/kernel/exit.c Tue Nov 20 10:00:26 2001
+++ linux-2.4.15-pre7-patch/kernel/exit.c Tue Nov 20 09:57:48 2001
@@ -544,8 +544,11 @@
                                 retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
                                 if (!retval && stat_addr)
                                         retval = put_user(p->exit_code, stat_addr);
- if (retval)
+ if (retval) {
+ /* Reset state. We're not cleaning up yet */
+ p->state = TASK_ZOMBIE;
                                         goto end_wait4;
+ }
                                 retval = p->pid;
                                 if (p->p_opptr != p->p_pptr) {
                                         write_lock_irq(&tasklist_lock);
@@ -553,6 +556,8 @@
                                         p->p_pptr = p->p_opptr;
                                         SET_LINKS(p);
                                         do_notify_parent(p, SIGCHLD);
+ /* Reset state. We're not cleaning up yet */
+ p->state = TASK_ZOMBIE;
                                         write_unlock_irq(&tasklist_lock);
                                 } else
                                         release_task(p);

-
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This archive was generated by hypermail 2b29 : Fri Nov 23 2001 - 21:00:23 EST