linux-kernel - Re: [PATCH 2/5] softlockup: make detector be aware of task switch of processes hogging cpu

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Message-ID: <20140818203801.GE49576@redhat.com>
Date:	Mon, 18 Aug 2014 16:38:08 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	akpm@...ux-foundation.org, kvm@...r.kernel.org,
	pbonzini@...hat.com, mingo@...hat.com,
	LKML <linux-kernel@...r.kernel.org>,
	chai wen <chaiw.fnst@...fujitsu.com>
Subject: Re: [PATCH 2/5] softlockup: make detector be aware of task switch of
 processes hogging cpu

On Mon, Aug 18, 2014 at 09:02:00PM +0200, Ingo Molnar wrote:
> 
> * Don Zickus <dzickus@...hat.com> wrote:
> 
> > > > > So I agree with the motivation of this improvement, but 
> > > > > is this implementation namespace-safe?
> > > > 
> > > > What namespace are you worried about colliding with?  I 
> > > > thought softlockup_ would provide the safety??  Maybe I 
> > > > am missing something obvious. :-(
> > > 
> > > I meant PID namespaces - a PID in itself isn't guaranteed 
> > > to be unique across the system.
> > 
> > Ah, I don't think we thought about that.  Is there a better 
> > way to do this?  Is there a domain id or something that can 
> > be OR'd with the pid?
> 
> What is always unique is the task pointer itself. We use pids 
> when we interface with user-space - but we don't really do that 
> here, right?

No, I don't believe so.  Ok, so saving 'current' and comparing that should
be enough, correct?

Cheers,
Don
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