From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755380Ab1IMIAO (ORCPT ); Tue, 13 Sep 2011 04:00:14 -0400 Received: from mail-yw0-f46.google.com ([209.85.213.46]:60968 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755339Ab1IMIAK (ORCPT ); Tue, 13 Sep 2011 04:00:10 -0400 Date: Tue, 13 Sep 2011 17:00:04 +0900 From: Tejun Heo To: Oleg Nesterov Cc: Denys Vlasenko , linux-kernel@vger.kernel.org, dvlasenk@redhat.com Subject: Re: [PATCH v2] Make PTRACE_SEIZE set ptrace options specified in 'data' parameter Message-ID: <20110913080004.GF11397@mtj.dyndns.org> References: <201109072340.31460.vda.linux@googlemail.com> <20110908004438.GC3987@mtj.dyndns.org> <20110908181747.GA28120@redhat.com> <20110911020523.GL29319@htj.dyndns.org> <20110911181442.GA22239@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110911181442.GA22239@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 11, 2011 at 08:14:42PM +0200, Oleg Nesterov wrote: > We need to rework the locking, yes. But we need the lock which protects > the parent's list_head (currently we rely on tasklist). Yes, a single > lock can't help. We already use ->cred_guard_mutex though. > > This needs more thinking, but imho child->siglock is pointless here. But we can at least guarantee that if ->ptrace is set (or clear) while tracee's siglock is held, its ->parent points to the tracer (or not). At any rate, AFAICS, this currently doesn't really matter. I suggested it mainly because it would make the locking change easier. Thanks. -- tejun