linux-kernel - Re: [PATCH 2/4] fanotify: Add pids to events

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Date:	Sat, 16 Jan 2010 19:44:04 -0800
From:	Matt Helsley <matthltc@...ibm.com>
To:	Andreas Gruenbacher <agruen@...e.de>
Cc:	Matt Helsley <matthltc@...ibm.com>,
	Matthew Helsley <matt.helsley@...il.com>,
	Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
	hch@...radead.org, containers@...ts.linux-foundation.org,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 2/4] fanotify: Add pids to events

On Sat, Jan 16, 2010 at 11:53:45PM +0100, Andreas Gruenbacher wrote:
> On Friday 15 January 2010 10:21:46 pm Matt Helsley wrote:
> > On Fri, Jan 15, 2010 at 04:12:09PM +0100, Andreas Gruenbacher wrote:
> > > > 2. If the event recipient does a clone and enters a new pidns the pid
> > > > number will be incorrect without any indication.
> > >
> > > No, if a process has a pid within the listener's namespace the listener
> > > will see this pid; otherwise, the resulting pid value is 0.
> > 
> > So the pid reference is resolved at read(), correct? If so then that's
> >  fine. (Otherwise I'd think the values could still become stale).
> 
> Yes.  Note that for non-blocking events, there is no guarantee that the 
> triggering process still runs when the event is consumed though.

Holding the reference until the event is read ensures the pid
won't be reused in that namespace, so I think that's fine.

Cheers,
	-Matt Helsley
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