Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756562AbZCJOvW (ORCPT ); Tue, 10 Mar 2009 10:51:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756318AbZCJOu5 (ORCPT ); Tue, 10 Mar 2009 10:50:57 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:50593 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756184AbZCJOu4 (ORCPT ); Tue, 10 Mar 2009 10:50:56 -0400 Date: Tue, 10 Mar 2009 15:50:36 +0100 From: Ingo Molnar To: Alan Stern Cc: prasad@linux.vnet.ibm.com, Andrew Morton , Linux Kernel Mailing List , Roland McGrath Subject: Re: [patch 01/11] Introducing generic hardware breakpoint handler interfaces Message-ID: <20090310145036.GI3850@elte.hu> References: <20090310135018.GB3850@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1655 Lines: 45 * Alan Stern wrote: > On Tue, 10 Mar 2009, Ingo Molnar wrote: > > > * prasad@linux.vnet.ibm.com wrote: > > > > > > > +static u8 tprio[HB_NUM]; /* Thread bp max priorities */ > > > +LIST_HEAD(kernel_bps); /* Kernel breakpoint list */ > > > +static LIST_HEAD(thread_list); /* thread_hw_breakpoint list */ > > > +DEFINE_PER_CPU(struct cpu_hw_breakpoint, cpu_bp); > > If nobody minds, I'll answer some of these questions on > Prasad's behalf because they address parts of the code that > were written before he took over the project. > > > hm, why do we need the whole 'priority' mechanism? It seems > > very over-designed to me. > > This was done at Roland McGrath's express request. We should > see what he has to say about it. > > > The likelyhood of both user-space and kernel-space to use > > hw-breakpoints is very low to begin with. And if they use > > them, the likelyhood of there being more than 4 debugregs > > required in the same context is even lower. > > Not all architectures have 4 debug registers. Most have only > one. > > > If that happens we shouldnt try to be too smart about them - > > just override user-space ones with kernel space ones and > > that's it. No explicit priorities are needed. > > Roland really did not want it done this way. Well i guess i'll have to wait for Roland's reply then. Ingo -- 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/