linux-kernel - Re: [PATCH 3/7] revoke: core code

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Message-Id: <1173612316.7330.3.camel@haji>
Date:	Sun, 11 Mar 2007 13:25:16 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	hch@...radead.org, alan@...rguk.ukuu.org.uk, serue@...ibm.com
Subject: Re: [PATCH 3/7] revoke: core code

On Fri, 2007-03-09 at 10:15 +0200, Pekka J Enberg wrote:
> > +  again:
> > +	restart_addr = zap_page_range(vma, start_addr, end_addr - start_addr,
> > +				      details);
> > +
> > +	need_break = need_resched() || need_lockbreak(details->i_mmap_lock);
> > +	if (need_break)
> > +		goto out_need_break;
> > +
> > +	if (restart_addr < end_addr) {
> > +		start_addr = restart_addr;
> > +		goto again;
> > +	}
> > +	return 0;
> > +
> > +  out_need_break:
> > +	spin_unlock(details->i_mmap_lock);
> > +	cond_resched();
> > +	spin_lock(details->i_mmap_lock);
> > +	return -EINTR;

On Fri, 2007-03-09 at 13:30 +0100, Peter Zijlstra wrote:
> I'm not sure this scheme works, given a sufficiently loaded machine,
> this might never complete.

Hmm, so what's the alternative? It's better to fail revoke than lock up
the box.

On Fri, 2007-03-09 at 13:30 +0100, Peter Zijlstra wrote:
> I'm never sure of operator precedence and prefer:
> 
>  (vma->vm_flags & VM_SHARED) && ...
> 
> which leaves no room for error.

Thanks, fixed.

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