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

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Message-ID: <20080306191051.GH28006@linux-os.sc.intel.com>
Date:	Thu, 6 Mar 2008 11:10:52 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Pavel Machek <pavel@....cz>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	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 Thu, Mar 06, 2008 at 04:51:41PM +0100, Ingo Molnar wrote:
> 
> * Pavel Machek <pavel@....cz> wrote:
> 
> > > > 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.
> 
> hm, how does it differ from any other allocation failure? We could fail 
> to allocate a pagetable page. We could fail to allocate the task_struct 
> to begin with.

Yes. This happens under out of memory conditions. And we are also using
GFP_KERNEL here, which can block.
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