From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752390AbaKCXDI (ORCPT ); Mon, 3 Nov 2014 18:03:08 -0500 Received: from mail-la0-f49.google.com ([209.85.215.49]:51840 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750905AbaKCXDF (ORCPT ); Mon, 3 Nov 2014 18:03:05 -0500 MIME-Version: 1.0 In-Reply-To: <20141103225721.GA12117@redhat.com> References: <20141103214712.GA8711@redhat.com> <20141103215837.GB8711@redhat.com> <20141103225721.GA12117@redhat.com> From: Andy Lutomirski Date: Mon, 3 Nov 2014 15:02:43 -0800 Message-ID: Subject: Re: [tip:x86/asm] sched/x86_64: Don't save flags on context switch To: Oleg Nesterov Cc: Jan Beulich , Ingo Molnar , Linus Torvalds , "H. Peter Anvin" , Sebastian Lackner , "linux-kernel@vger.kernel.org" , Chuck Ebbert , Anish Bhatt , Thomas Gleixner , "linux-tip-commits@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 3, 2014 at 2:57 PM, Oleg Nesterov wrote: > Argh, sorry for confusion... > > On 11/03, Andy Lutomirski wrote: >> >> On Mon, Nov 3, 2014 at 1:58 PM, Oleg Nesterov 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". But this is checking whether interrupts were on in the frame we're returning to, not whether they're on right now, right? --Andy