From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261157AbULJUpi (ORCPT ); Fri, 10 Dec 2004 15:45:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261181AbULJUpi (ORCPT ); Fri, 10 Dec 2004 15:45:38 -0500 Received: from mustang.oldcity.dca.net ([216.158.38.3]:64932 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S261157AbULJUpe (ORCPT ); Fri, 10 Dec 2004 15:45:34 -0500 Subject: Re: RCU question From: Lee Revell To: dipankar@in.ibm.com Cc: George Anzinger , ganzinger@mvista.com, Manfred Spraul , lkml In-Reply-To: <20041210204003.GC4073@in.ibm.com> References: <41B8E6F1.4070007@mvista.com> <20041210043102.GC4161@in.ibm.com> <41B9FC3F.50601@mvista.com> <20041210204003.GC4073@in.ibm.com> Content-Type: text/plain Date: Fri, 10 Dec 2004 15:45:31 -0500 Message-Id: <1102711532.29919.35.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2004-12-11 at 02:10 +0530, Dipankar Sarma wrote: > On Fri, Dec 10, 2004 at 11:42:55AM -0800, George Anzinger wrote: > > Dipankar Sarma wrote: > > >And yes, RCU processing in softirq context can re-raise the softirq. > > >AFAICS, it is perfectly normal. > > > > My assumption was that, this being the idle task, RCU would be more than > > happy to finish all its pending tasks. > > We try to avoid really long running softirqs (RCU tasklet in this case) > for better scheduling latency. A long running rcu tasklet during > an idle cpu may delay running of an RT process that becomes runnable > during the rcu tasklet. > Well, softirqs should really be preemptible if you care about RT task latency. Ingo's patches have had this for months. Works great. Maybe it's time to push it upstream. Lee