Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753786AbbHUGXe (ORCPT ); Fri, 21 Aug 2015 02:23:34 -0400 Received: from mail-wi0-f169.google.com ([209.85.212.169]:37048 "EHLO mail-wi0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753764AbbHUGXc (ORCPT ); Fri, 21 Aug 2015 02:23:32 -0400 Date: Fri, 21 Aug 2015 08:23:28 +0200 From: Ingo Molnar To: Andy Lutomirski Cc: x86@kernel.org, Sasha Levin , Brian Gerst , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Denys Vlasenko , linux-kernel@vger.kernel.org, Oleg Nesterov , Borislav Petkov , Thomas Gleixner Subject: Re: [PATCH] x86/traps: Weaken context tracking entry assertions Message-ID: <20150821062328.GA32366@gmail.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 965 Lines: 26 * Andy Lutomirski wrote: > We were asserting that we were all the way in CONTEXT_KERNEL when exception > handlers were called. While having this be true is, I think, a nice goal (or > maybe a variant in which we assert that we're in CONTEXT_KERNEL or some new IRQ > context), we're not quite there. > > In particular, if an IRQ interrupts the SYSCALL prologue and the IRQ handler in > turn causes an exception, the exception entry will be called in RCU IRQ mode but > with CONTEXT_USER. Hm, so what harm would there be in making IRQ handlers enter CONTEXT_KERNEL? Would nohz-full break? I'd rather have a bit more tracking overhead here than lose such useful sanity checks. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/