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

Dave McCracken
2001-11-20T16:09:05Z

--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);