linux-kernel - Re: [PATCH v3 2/2] x86_64: Don't save flags on context switch

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Date:	Wed, 01 Oct 2014 11:35:27 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
	Ingo Molnar <mingo@...hat.com>
CC:	Sebastian Lackner <sebastian@...-team.de>,
	Anish Bhatt <anish@...lsio.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chuck Ebbert <cebbert.lkml@...il.com>
Subject: Re: [PATCH v3 2/2] x86_64: Don't save flags on context switch

On 10/01/2014 11:28 AM, Andy Lutomirski wrote:
>  
>  #define __EXTRA_CLOBBER  \
>  	, "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \
> -	  "r12", "r13", "r14", "r15"
> +	  "r12", "r13", "r14", "r15", "flags"
>  

I was under the impression that gcc *always* assumes the flags were
clobbered for an asm statement.  Otherwise I think we'd have a lot of
problems.

	-hpa


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