linux-kernel - Re: [RFT PATCH v2 3/4] arm64: reduce duplicated code when saving/restoring FPSIMD for signal handling

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Date:	Tue, 15 Oct 2013 00:01:20 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Will Deacon <Will.Deacon@....com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christopher Covington <cov@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH v2 3/4] arm64: reduce duplicated code when saving/restoring
 FPSIMD for signal handling

On 10/14/2013 11:44 PM, Catalin Marinas wrote:
> On Sun, Oct 13, 2013 at 03:20:19PM +0100, Jiang Liu wrote:
>> +void fpsimd_prepare_sigctx(struct fpsimd_state *state)
>> +{
>> +	/* dump the hardware registers to the fpsimd_state structure */
>> +	fpsimd_save_state(state);
>> +	fpsimd_clear_fpsr();
>> +}
> 
> What don't particularly like is that you save the FP context and then
> corrupt it. Can we get preempted after this function and before we save
> it on the signal stack?
> 
Yeah, good point!
There's a race window to get preempted, will fix it.
Thanks!
Gerry

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