Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269974AbUJNFGW (ORCPT ); Thu, 14 Oct 2004 01:06:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269976AbUJNFGW (ORCPT ); Thu, 14 Oct 2004 01:06:22 -0400 Received: from e31.co.us.ibm.com ([32.97.110.129]:3061 "EHLO e31.co.us.ibm.com") by vger.kernel.org with ESMTP id S269974AbUJNFGS (ORCPT ); Thu, 14 Oct 2004 01:06:18 -0400 Date: Thu, 14 Oct 2004 10:39:05 +0530 From: Dipankar Sarma To: Ingo Molnar Cc: Sven Dietrich , Daniel Walker , Andrew Morton , linux-kernel@vger.kernel.org, abatyrshin@ru.mvista.com, amakarov@ru.mvista.com, emints@ru.mvista.com, ext-rt-dev@mvista.com, hzhang@ch.mvista.com, yyang@ch.mvista.com, "Witold. Jaworski@Unibw-Muenchen. De" , arnd.heursch@unibw-muenchen.de Subject: Re: [ANNOUNCE] Linux 2.6 Real Time Kernel Message-ID: <20041014050905.GA6927@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20041011215420.GA19796@elte.hu> <20041012055029.GB1479@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041012055029.GB1479@elte.hu> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 34 On Tue, Oct 12, 2004 at 07:50:29AM +0200, Ingo Molnar wrote: > > regarding RCU serialization - i think that is the way to go - i dont > think there is any sensible way to extend RCU to a fully preempted > model, RCU is all about per-CPU-ness and per-CPU-ness is quite limited > in a fully preemptible model. It seems that way to me too. Long ago I implemented preemptible RCU, but did not follow it through because I believed it was not a good idea. The original patch is here : http://www.uwsg.iu.edu/hypermail/linux/kernel/0205.1/0026.html This allows read-side critical sections of RCU to be preempted. It will take a bit of work to re-use it in RCU as of now, but I don't think it makes sense to do so. My primary concern is DoS/OOM situation due to preempted tasks holding up RCU. > > could you send those RCU patches (no matter how incomplete/broken)? It's > the main issue that causes the dcache_lock to be raw still. (and a > number of dependent locks: fs-writeback.c, inode.c, etc.) We can make > those RCU changes not impact the normal !PREEMPT_REALTIME locking so it > might have a chance for upstream merging as well. I would be interested in this too. Thanks Dipankar - 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/