From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20968 invoked by alias); 5 May 2011 15:21:41 -0000 Received: (qmail 20921 invoked by uid 22791); 5 May 2011 15:21:39 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mail.codesourcery.com (HELO mail.codesourcery.com) (38.113.113.100) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 05 May 2011 15:21:24 +0000 Received: (qmail 13846 invoked from network); 5 May 2011 15:21:23 -0000 Received: from unknown (HELO scottsdale.localnet) (pedro@127.0.0.2) by mail.codesourcery.com with ESMTPA; 5 May 2011 15:21:23 -0000 From: Pedro Alves To: "Ulrich Weigand" Subject: Re: [RFA 2/3] Demote to sw watchpoint only in update_watchpoint Date: Thu, 05 May 2011 15:21:00 -0000 User-Agent: KMail/1.13.5 (Linux/2.6.35-28-generic; KDE/4.6.2; x86_64; ; ) Cc: Thiago Jung Bauermann , Eli Zaretskii , gdb-patches@sourceware.org References: <201105051110.p45BA6Jm013405@d06av02.portsmouth.uk.ibm.com> In-Reply-To: <201105051110.p45BA6Jm013405@d06av02.portsmouth.uk.ibm.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201105051621.42627.pedro@codesourcery.com> X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2011-05/txt/msg00135.txt.bz2 On Thursday 05 May 2011 12:10:05, Ulrich Weigand wrote: > Pedro Alves wrote: > > On Wednesday 04 May 2011 23:20:48, Thiago Jung Bauermann wrote: > > > Pedro's suggestion: > > > > > > 1. The inferior is stopped and software bp_locations (both breakpoints > > > and watchpoints) are removed. Hardware ones stay in place. > > > 2. The user asks for a new watchpoint. > > > 3. GDB evaluates the expression and creates the bp_locations. > > > 4. GDB tries to insert the bp_locations as hw watches. If that fails, > > > then converts to sw and registers the watchpoint for insertion. > > > 5. The user asks the inferior to be continued. > > > 6. GDB inserts sw breakpoints and watchpoints and resumes the inferior. > > > > Either that or try keep hardware breakpoints and watchpoints uninserted, > > and insert them just before 4. This variant is a bit safer in case GDB crashes, > > but is a bit less efficient in case there are many watchpoints. But then > > again we already remove/insert them all at each step, so that is kind of moot. > > I've no real preference on which. This is a minor detail in the grand scheme > > from my perspective. > > One thing I'm wondering about is the comment before update_watchpoints: > > Even with `set breakpoint always-inserted on' the watchpoints are > removed + inserted on each stop here Normal breakpoints must > never be removed because they might be missed by a running thread > when debugging in non-stop mode. On the other hand, hardware > watchpoints (is_hardware_watchpoint; processed here) are specific > to each LWP since they are stored in each LWP's hardware debug > registers. Therefore, such LWP must be stopped first in order to > be able to modify its hardware watchpoints. > [etc.] > > Is this still valid, and would it affect this current discussion if so? This is stale. Watchpoints are no longer removed/inserted on each stop with always-inserted on. It needed fixing for watchpoints+non-stop. linux gdbserver copes with inserting breakpoints/watchpoints when threads are running. Native linux doesn't, but that just it doesn't really fully support watchpoints in non-stop mode currently. -- Pedro Alves