linux-kernel - Re: [tip:x86/asm] sched/x86_64: Don't save flags on context switch

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Message-ID: <20141103225721.GA12117@redhat.com>
Date:	Mon, 3 Nov 2014 23:57:21 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Jan Beulich <jbeulich@...e.com>, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Sebastian Lackner <sebastian@...-team.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chuck Ebbert <cebbert.lkml@...il.com>,
	Anish Bhatt <anish@...lsio.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/asm] sched/x86_64: Don't save flags on context switch

Argh, sorry for confusion...

On 11/03, Andy Lutomirski wrote:
>
> On Mon, Nov 3, 2014 at 1:58 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> > On 11/03, Oleg Nesterov wrote:
> >>
> > Btw, why retint_kernel() checks "interrupts on" ? It seems to me that
> > that "interrupts off" is not possible, no? And this will be more clear
> > when we remove the "exit_intr" label.
>
> We might get there from #MC or from any of a number of synchronous
> errors (#GP from xyz_safe, #PF from some atomic uaccess thing or a
> vmap fault, etc), and all of those have interrupts off.

Yes, yes, exactly.

I actually tried to say that irqs should be always disabled (afaics!).
IOW "interrupts on" should not be possible, not "interrupts off".

Oleg.

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