linux-kernel - Re: [PATCH 3/2 -v3] fcntl: F_[SG]ETOWN

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Date:	Tue, 4 Aug 2009 19:19:05 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, eranian@...il.com,
	mingo@...e.hu, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	robert.richter@....com, paulus@...ba.org, andi@...stfloor.org,
	mpjohn@...ibm.com, cel@...ibm.com, cjashfor@...ibm.com,
	mucci@...s.utk.edu, terpstra@...s.utk.edu,
	perfmon2-devel@...ts.sourceforge.net, mtk.manpages@...glemail.com,
	roland@...hat.com
Subject: Re: [PATCH 3/2 -v3] fcntl: F_[SG]ETOWN_EX

On 08/04, Peter Zijlstra wrote:
>
> On Tue, 2009-08-04 at 18:20 +0200, Oleg Nesterov wrote:
>
> > > +	rcu_read_lock();
> > > +	pid = find_vpid(owner.pid);
> > > +	ret = __f_setown(filp, pid, type, 1);
> > > +	rcu_read_unlock();
> > > +
> > > +	return ret;
> >
> > Perhaps it makes sense to return -ESRCH if owner.pid && !pid, not
> > sure.
>
> We'd need that case to unset/clear the owner, so returning -ESRCH might
> confuse users I think.

Agreed. Perhaps we should do nothing but return -ESRCH if user passes
owner->pid != 0 and it is not valid.

But this is minor and can be tweaked later. (and to clarify again, not
that I really think we should do this, just a random thought).

> How about the below delta, it changes send_sigurg_to_task() to also use
> do_send_sig_info() which looses the check_kill_permission() check, but
> your previous changes lost that same thing from SIGIO -- so I'm hoping
> that's ok.

Yes, I think this is fine!

Oleg.

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