From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757468AbZCMJZ3 (ORCPT ); Fri, 13 Mar 2009 05:25:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752831AbZCMJZU (ORCPT ); Fri, 13 Mar 2009 05:25:20 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:22074 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751517AbZCMJZT convert rfc822-to-8bit (ORCPT ); Fri, 13 Mar 2009 05:25:19 -0400 Message-Id: <49BA33BE.76E4.0078.0@novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.0 Date: Fri, 13 Mar 2009 09:21:50 +0000 From: "Jan Beulich" To: , "Peter Zijlstra" , , , Cc: Subject: Re: [tip:core/ipi] generic-ipi: eliminate spurious pointlessWARN_ON()s References: <49B91A7E.76E4.0078.0@novell.com> <1236934491.5188.209.camel@laptop> In-Reply-To: <1236934491.5188.209.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> Peter Zijlstra 13.03.09 09:54 >>> >Wouldn't leaving them in place but changing them to: > >WARN_ON(irqs_disabled() && system_state == SYSTEM_RUNNING); > >be clearer? I don't think that would be precise: system_state gets set to SYSTEM_RUNNING much later than APs get brought up (i.e. there are cases where the WARN_ON()s could validly trigger with SYSTEM_BOOTING), and also doesn't cover states > SYSTEM_RUNNING (where, again, after perhaps having brought down all APs the warnings could become pointless, but the warnings could be meaningful as long as there are still some APs online). While from an abstract code reading perspective your suggestion might seem reasonable, the changed placement really reflects what the warning is trying to warn about - a potential deadlock which cannot occur under the conditions filtered out by conditionals the warnings were moved beyond. Jan