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

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Message-ID: <47D1352F.6010504@zytor.com>
Date:	Fri, 07 Mar 2008 04:29:35 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Pavel Machek <pavel@....cz>
CC:	Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Christoph Hellwig <hch@...radead.org>, 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

Pavel Machek wrote:
> On Thu 2008-03-06 16:51:41, 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 
> 
> Well, we should not be sending SIGSEGV...? SIGBUS would be cleaner, or
> SIGKILL... what happens when userland tries to catch this one?
> 

I'm confused...

Normally when we need memory for userspace and can't get it, we put the 
process to sleep until memory is available.

Why is this different in any way?

	-hpa
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