From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758893Ab1IINBc (ORCPT ); Fri, 9 Sep 2011 09:01:32 -0400 Received: from smarthost1.greenhost.nl ([195.190.28.78]:52010 "EHLO smarthost1.greenhost.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758817Ab1IINBa (ORCPT ); Fri, 9 Sep 2011 09:01:30 -0400 Message-ID: <661eb210adc223ac1eb80777df48b226.squirrel@webmail.greenhost.nl> In-Reply-To: <93a9bd6624aa6a991d688bfaba766a91.squirrel@webmail.greenhost.nl> References: <1315500802.18043.45.camel@dhcp-25-63.brq.redhat.com> <20110909001853.GA29319@htj.dyndns.org> <201109090754.50272.vda.linux@googlemail.com> <93a9bd6624aa6a991d688bfaba766a91.squirrel@webmail.greenhost.nl> Date: Fri, 9 Sep 2011 15:01:28 +0200 Subject: Re: Why I want PTRACE_O_TRACESTOP option From: "Indan Zupancic" To: "Indan Zupancic" Cc: "Denys Vlasenko" , "Tejun Heo" , "Denys Vlasenko" , "Oleg Nesterov" , linux-kernel@vger.kernel.org User-Agent: SquirrelMail/1.4.22 MIME-Version: 1.0 Content-Type: text/plain;charset=UTF-8 Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal X-Spam-Score: 0.0 X-Scan-Signature: 1fac81774939798d1cdb19633eb460de Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, September 9, 2011 14:26, Indan Zupancic wrote: > Hello, > > On Fri, September 9, 2011 07:54, Denys Vlasenko wrote: >> On Friday 09 September 2011 02:18, Tejun Heo wrote: >>> Hello, Denys. >>> >>> On Thu, Sep 08, 2011 at 06:50:01PM +0200, Denys Vlasenko wrote: >>> > Consider what will happen when a next ptrace fix will require >>> > a way to change ptrace API at runtime. A new option will likely >>> > be introduced, say, PTRACE_O_TRACEPONY, with next available >>> > bit position 7, and perhaps some new event will be generated, >>> > PTRACE_EVENT_PONY, with value.... yes, it can't be 7, >>> > PTRACE_EVENT_STOP took it. So it will probably be 8. >>> >>> Then, just give it the next matching number. >> >> My point is that previously, ptrace behavior was modified by setting >> options. Why don't we use this mechanism? Why we invent a different >> wheel? Ptrace is ugly as-is, why complicate it even further? >> >> The argument was that SETOPTIONS wasn't suitable for modifying >> attach behavior, but this is fixed by "set options on SEIZE" >> patch. I don't see why we can't use options mechanist to affect >> group-stop behavior now. > > I totally agree with Denys here. > > It is very useful to set options atomically at SEIZE time. Having > SEIZE set some hidden option implicitly only makes things more > confusing and harder to explain what SEIZE does. Please apply Denys' > SEIZE API improvements. > > Another important reason to make PTRACE_O_TRACESTOP an option is > because not everyone uses SEIZE: Users using PTRACE_TRACEME can't > set this option at all. For those PTRACE_O_TRACESTOP is needed. > Using PTRACE_TRACEME is the common case for both strace and gdb. PTRACE_O_TRACESTOP only makes sense if it also affects auto-attach SIGSTOPS, of course. I don't know if it does. It probably should. Indan