From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754214AbZBXEDn (ORCPT ); Mon, 23 Feb 2009 23:03:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752323AbZBXEDe (ORCPT ); Mon, 23 Feb 2009 23:03:34 -0500 Received: from smtp102.mail.mud.yahoo.com ([209.191.85.212]:47386 "HELO smtp102.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751711AbZBXEDe (ORCPT ); Mon, 23 Feb 2009 23:03:34 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=DFeXoPo+Llx6GLUVIaQbt/bpS1jffT+uYgDxOq4eD5oxHPpqiyuFtwHzDH/qUqMzr6IzjYV2m0UKzi0ZyNs22rmFo4HcV06QyJrRkO99lInqP9NUgZ/DVh37/XKBYjH/vb0ZO6YCJCxe4wWnocP2AsDjdlsEzBHsuMV3pSqNtuY= ; X-YMail-OSG: dZdLdCIVM1mGD3bjOBImiQUMOTM80U.Eh6ykI_oz2sM_UcMfkoOLPRgwuflsuParQnwTIaIWCbJV_In5cgLUfFj6VIIvI7UzaBFwQWkWO.YGAnuv4WfcqWUTwnIkjMqSZjmDUhjYy2w4Mtm6GOujhUSWInm3uajosj9W_jz9BsXyVXvire4VgY1FVjMeUQ-- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: paulmck@linux.vnet.ibm.com Subject: Re: [PATCH] v2 Teach RCU that idle task is not quiscent state at boot Date: Tue, 24 Feb 2009 15:02:56 +1100 User-Agent: KMail/1.9.51 (KDE/4.0.4; ; ) Cc: linux-kernel@vger.kernel.org, vegard.nossum@gmail.com, mingo@elte.hu, stable@kernel.org, akpm@linux-foundation.org, npiggin@suse.de, penberg@cs.helsinki.fi References: <20090223161611.GA9563@linux.vnet.ibm.com> <20090223204332.GA19861@linux.vnet.ibm.com> In-Reply-To: <20090223204332.GA19861@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200902241502.57833.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 24 February 2009 07:43:32 Paul E. McKenney wrote: > @@ -80,6 +81,10 @@ void wakeme_after_rcu(struct rcu_head *head) > void synchronize_rcu(void) > { > struct rcu_synchronize rcu; > + > + if (num_online_cpus() == 1) > + return; /* If UP, synchronize_rcu() is a grace period! */ > + Nice patch... May I just suggest a comment to say that this is also a correctness requirement due to the grace period holdoff for early boot?