linux-kernel - Re: [patch 2/2] x86, fpu: lazy allocation of FPU area

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Message-ID: <20080305194705.GA4386@ucw.cz>
Date:	Wed, 5 Mar 2008 20:47:06 +0100
From:	Pavel Machek <pavel@....cz>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Christoph Hellwig <hch@...radead.org>,
	hpa@...or.com, tglx@...utronix.de, andi@...stfloor.org,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [patch 2/2] x86, fpu: lazy allocation of FPU area - v3

On Tue 2008-03-04 09:55:28, Suresh Siddha wrote:
> On Tue, Mar 04, 2008 at 11:32:20AM +0100, Ingo Molnar wrote:
> > 
> > * Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> > 
> > > On Mon, Mar 03, 2008 at 08:20:12PM -0500, Christoph Hellwig wrote:
> > > > On Mon, Mar 03, 2008 at 03:02:46PM -0800, Suresh Siddha wrote:
> > > > > +	/*
> > > > > +	 * Memory allocation at the first usage of the FPU and other state.
> > > > > +	 */
> > > > > +	if (!tsk->thread.xstate)
> > > > > +		tsk->thread.xstate = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
> > > >
> > > >  Also don't we need some kind of error handling here?
> > > 
> > > Currently it uses SLAB_PANIC.
> > 
> > but SLAB_PANIC only covers kmem_cache_create() failures. 
> > 
> > kmem_cache_alloc() can fail (return NULL) and not handling it is a bug.
> 
> oops. you are correct. Will send a sigsegv in the failure case then. Thanks.

You are introducing possibility of hard to debug error, where previous
code just worked... Does not look like good idea to me.
-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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