From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764748AbYECRRg (ORCPT ); Sat, 3 May 2008 13:17:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761148AbYECRR1 (ORCPT ); Sat, 3 May 2008 13:17:27 -0400 Received: from mx1.redhat.com ([66.187.233.31]:55194 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759712AbYECRR0 (ORCPT ); Sat, 3 May 2008 13:17:26 -0400 Date: Sat, 3 May 2008 13:16:27 -0400 From: "Frank Ch. Eigler" To: Clark Williams Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Subject: Re: preempt-rt, need old style rwlocks for systemtap Message-ID: <20080503171627.GC23961@redhat.com> References: <20080503132327.GA28881@redhat.com> <481C77E8.8050002@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <481C77E8.8050002@redhat.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi - On Sat, May 03, 2008 at 09:34:16AM -0500, Clark Williams wrote: > [...] > > It has come to my attention that the preempt-rt patch suite > > deliberately defeats the potential concurrency intended by systemtap's > > use of rwlocks to permit concurrent readers [...] > The reason it "defeats" the concurrent behavior is that it's really > complicated to have concurrent readers with Priority Inheritance, so > the initial cut of rtmutexes serialized all lock accesses. [...] Do you believe priority inheritance to be an essential property of every use of these primitives, regardless of the nature of the specifical critical sections being protected? Is there no way & need to opt out of the extra machinery? - FChE