From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763206AbYBUQm0 (ORCPT ); Thu, 21 Feb 2008 11:42:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751277AbYBUQmB (ORCPT ); Thu, 21 Feb 2008 11:42:01 -0500 Received: from ns2.suse.de ([195.135.220.15]:50951 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755156AbYBUQl7 (ORCPT ); Thu, 21 Feb 2008 11:41:59 -0500 From: Andi Kleen Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg) To: Gregory Haskins Subject: Re: [PATCH [RT] 11/14] optimize the !printk fastpath through the lock acquisition Date: Thu, 21 Feb 2008 17:36:25 +0100 User-Agent: KMail/1.9.6 Cc: mingo@elte.hu, a.p.zijlstra@chello.nl, tglx@linutronix.de, rostedt@goodmis.org, linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, bill.huey@gmail.com, kevin@hilman.org, cminyard@mvista.com, dsingleton@mvista.com, dwalker@mvista.com, npiggin@suse.de, dsaxena@plexity.net, gregkh@suse.de, sdietrich@novell.com, pmorreale@novell.com, mkohari@novell.com References: <20080221152504.4804.8724.stgit@novell1.haskins.net> <20080221152722.4804.77478.stgit@novell1.haskins.net> In-Reply-To: <20080221152722.4804.77478.stgit@novell1.haskins.net> MIME-Version: 1.0 Content-Disposition: inline Message-Id: <200802211736.26719.ak@suse.de> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 21 February 2008 16:27:22 Gregory Haskins wrote: > @@ -660,12 +660,12 @@ rt_spin_lock_fastlock(struct rt_mutex *lock, > void fastcall (*slowfn)(struct rt_mutex *lock)) > { > /* Temporary HACK! */ > - if (!current->in_printk) > - might_sleep(); > - else if (in_atomic() || irqs_disabled()) > + if (unlikely(current->in_printk) && (in_atomic() || irqs_disabled())) I have my doubts that gcc will honor unlikelies that don't affect the complete condition of an if. Also conditions guarding returns are by default predicted unlikely anyways AFAIK. The patch is likely a nop. -Andi