Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754584Ab1FCL60 (ORCPT ); Fri, 3 Jun 2011 07:58:26 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:51180 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753654Ab1FCL6Z (ORCPT ); Fri, 3 Jun 2011 07:58:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=from:to:subject:date:user-agent:cc:references:in-reply-to :mime-version:content-type:content-transfer-encoding :content-disposition:message-id; b=p2Az/rjVWYubZGZWTa2wYWacNx+ZHX8F2jC1YRfVUEq70TAubKYOIKwhs9u4jWZeNI qx08Pdjlr0kqZzwhAV9RDpyA5XcK+Gbh+C2Rkf+oCJTONL5eNG787K8Y66miSNncuz0F bwPc3TCX11OS62upUA0vUPGPOd7ECRyaniQ/A= From: Denys Vlasenko To: Tejun Heo Subject: Re: [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification, take#4 Date: Fri, 3 Jun 2011 13:58:20 +0200 User-Agent: KMail/1.8.2 Cc: Oleg Nesterov , jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu, bdonlan@gmail.com, pedro@codesourcery.com References: <1306710760-16440-1-git-send-email-tj@kernel.org> <20110603013423.GB14872@mtj.dyndns.org> <201106031337.11615.vda.linux@googlemail.com> In-Reply-To: <201106031337.11615.vda.linux@googlemail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <201106031358.20857.vda.linux@googlemail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1820 Lines: 46 On Friday 03 June 2011 13:37, Denys Vlasenko wrote: > On Friday 03 June 2011 03:34, Tejun Heo wrote: > > > This should alleviate Linus' concerns that we are suffering from unnecessary > > > featuritis - that we invent API which is significantly different > > > from existing one, and as such users will not use it. > > > > > > Existing API doesn't use GETSIGINFO data per se to distinguish group-stop from > > > signal-delivery-stop, it uses the fact that GETSIGINFO fails on group-stop. > > > (Well, arguably it's not a "designed" API, more like "accidentally created API", > > > but nevertheless it exists right now). Oleg's proposal means that the new way > > > may be makde to work very similarly. > > > > Okay, you want to preserve %NULL SIGINFO on all STOP traps. Dropping > > si_pt_flags and using exit_code makes sense but I think we'll be > > better off enabling GETSIGINFO. The affected part of code has to be > > changed anyway > > Well, not exactly. The affected part of code in strace *has been changed > already*. Latest version of strace finally does show "SIGSTOP delivered" > and "group-stop happened" events differently. > > Now strace, ideally, can have a minimal change > > - ptrace(PTRACE_LISTEN, pid, 0, sig); > + if (this_is_group_stop) > + ptrace(PTRACE_LISTEN, pid, 0, 0); > + else > + ptrace(PTRACE_SYSCALL, pid, 0, sig); > > and boom, group-stops are handled correctly! I meant - ptrace(PTRACE_SYSCALL, pid, 0, sig); + if (this_is_group_stop) + ptrace(PTRACE_LISTEN, pid, 0, 0); + else + ptrace(PTRACE_SYSCALL, pid, 0, sig); -- vda -- 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/