From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933468AbaKSXXS (ORCPT ); Wed, 19 Nov 2014 18:23:18 -0500 Received: from mail-vc0-f171.google.com ([209.85.220.171]:33293 "EHLO mail-vc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932143AbaKSXXR (ORCPT ); Wed, 19 Nov 2014 18:23:17 -0500 MIME-Version: 1.0 In-Reply-To: References: <20141119192928.GL12538@two.firstfloor.org> Date: Wed, 19 Nov 2014 15:23:16 -0800 X-Google-Sender-Auth: 8YHi2-qQjml0oKkMhabSv_ElGxU Message-ID: Subject: Re: [PATCH v3 3/3] sched, x86: Check that we're on the right stack in schedule and __might_sleep From: Linus Torvalds To: Andy Lutomirski Cc: Andi Kleen , Borislav Petkov , "the arch/x86 maintainers" , Linux Kernel Mailing List , Peter Zijlstra , Oleg Nesterov , Tony Luck 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 Wed, Nov 19, 2014 at 3:04 PM, Andy Lutomirski wrote: > > Does that include nmi? I'm a bit afraid of touching that code. NMI is kind of special, since it's really not supposed to touch 'current' or anything like that, and that's how we do preempt-count (and that's where irq-count is) right now. I would prefer to have preempt_count be a percpu variable rather than a per-thread one, but there are historical reasons for that horror. Oh well. > It's certainly easy enough to bump irq_count in the paranoid entries. It definitely shouldn't be done from the assembly code. Usually it's "irq_enter/exit()" that does it, but for NMI you'd presumably just do it explicitly from do_nmi() or similar. But NMI really is nastier than other cases, see above. (That said, I thought we did it anyway, but now that I look I can't find it. So I was probably just smoking something) Linus