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

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Date:	Tue, 20 Feb 2007 20:20:49 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	akpm@...ux-foundation.org, roland@...hat.com,
	Michael Kerrisk <mtk-manpages@....net>
Subject: Re: [PATCH] fix handling of SIGCHILD from reaped child

On 02/21, KAMEZAWA Hiroyuki wrote:
>
> On Tue, 20 Feb 2007 17:22:57 +0300
> Oleg Nesterov <oleg@...sign.ru> 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.

Yes, it would be nice to know what maintainers think. This is a user visible
change, even if good.

> > > +		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.)

Probably it is me who misunderstands SUSv3. Could you point me the reference
to authoritative document? My understanding: if blocked AND wait() succeeds.

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

Yes. But sig-child-handler should do

	while (wait() >= 0)
		....

anyway, because SIGCHLD is not a realtime signal.

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

I just don't know... (Michael Kerrisk cc'ed).

Oleg.

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