linux-kernel - Re: [PATCH] x86-64, espfix: consider IRQs are off when initializing

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Message-ID: <53C7F063.7030007@zytor.com>
Date:	Thu, 17 Jul 2014 08:48:51 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Sasha Levin <sasha.levin@...cle.com>
CC:	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86-64, espfix: consider IRQs are off when initializing

On 07/17/2014 08:13 AM, Sasha Levin wrote:
> When going through our initialization code (init_espfix_ap() ) we need to
> keep in mind IRQs are off, and we need to handle it appropriately:
> 
>  - Do not allocate with __GFP_FS.
>  - No point in using a mutex.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>

I don't think this is safe.  The whole point was that if we do
GFP_ATOMIC we have to accept failure, and if we have a spin lock then
sleeping is not permitted.  It is unclear to me is sleeping is safe in
this context even so, so we may still have a problem, but calling
__get_free_page(GFP_ATOMIC) and then unconditionally use the results is
not right.

	-hpa

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