Re: [PATCH] fix handling of SIGCHILD from reaped child

From: KAMEZAWA Hiroyuki
Date: Tue Feb 20 2007 - 10:26:30 EST


On Tue, 20 Feb 2007 17:22:57 +0300
Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

>
> I'd suggest to make a separate function, but not complicate collect_signal().
>
okay. I'll try again if people admit me to go ahead.

> > --- linux-2.6.20-devel.orig/kernel/exit.c
> > +++ linux-2.6.20-devel/kernel/exit.c
> > @@ -1252,8 +1252,12 @@ static int wait_task_zombie(struct task_
> > }
> > write_unlock_irq(&tasklist_lock);
> > }
> > - if (p != NULL)
> > + if (p != NULL) {
> > release_task(p);
> > + /* if we received sigchild from "p" and p is released,
> > + we remove sigchild from it. */
>
> current may be ptracer, not a parent. Should be ok, clear_stale_sigchild(pid)
> can't have a false positive (until we have namespace for pid_t), but the comment
> is misleading a bit.
>
I'll rewrite and make this clearer.

> > + clear_stale_sigchild(current, retval);
>
> But we are not checking that SIGCHLD is blocked?
>
I'm sorry if I don't read SUSv3 correctly. SUSv3 doesn't define how we should
do if SIGCHLD is not blocked.(so I don't check not-blocked case.)

IMHO, user's sig-child-handler is tend to call wait()/waitpid() and expects
successful return. So removing stale signal here may be good.

If this breaks assumptions of applications on Linux, I'll not go eagerly.

Thanks,
-Kame





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