Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755908AbZCJOUB (ORCPT ); Tue, 10 Mar 2009 10:20:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754976AbZCJOTu (ORCPT ); Tue, 10 Mar 2009 10:19:50 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:47219 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754951AbZCJOTt (ORCPT ); Tue, 10 Mar 2009 10:19:49 -0400 Date: Tue, 10 Mar 2009 10:19:47 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Ingo Molnar 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 In-Reply-To: <20090310135018.GB3850@elte.hu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1488 Lines: 40 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. Alan Stern -- 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/