Re: [patch] inherited events not signalling parent on overflow

From: Vince Weaver <vincent.weaver@maine.edu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org, eranian@google.com,
	Paul Mackerras <paulus@samba.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [patch] inherited events not signalling parent on overflow
Date: Fri, 31 Jul 2015 00:42:06 -0400 (EDT)	[thread overview]
Message-ID: <alpine.DEB.2.20.1507310039390.25091@vincent-weaver-1.umelst.maine.edu> (raw)
In-Reply-To: <1434011521.1495.71.camel@twins>

On Thu, 11 Jun 2015, Peter Zijlstra wrote:

> Right, I had a peek earlier at how fasync worked but came away confused.
> 
> Today I seem to have had better luck. Installing fasync allocates memory
> and sets filp->f_flags |= FASYNC, which upon the demise of the file
> descriptor ensures the allocation is freed.
> 
> Now for perf, we can have the events stick around for a while after the
> original FD is dead because of references from child events. With the
> above patch these events would still have a pointer into this free'd
> fasync. This is bad.
> 
> A further problem with the patch is that if the parent changes its
> fasync state the children might lag and again have pointers into dead
> space.
> 
> All is not lost though; does something like the below work?

I had meant to reply to this earlier but maybe I forgot.

I've been running with this patch for a month now and haven't had 
problems, and it fixes the issue of inherited signals.  So it no one else 
has issues with the patch it would be nice if it could be pushed upstream.

Thanks,

Vince