From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754407AbcEaOS2 (ORCPT ); Tue, 31 May 2016 10:18:28 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:44617 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753692AbcEaOS0 (ORCPT ); Tue, 31 May 2016 10:18:26 -0400 Date: Tue, 31 May 2016 15:18:17 +0100 From: Russell King - ARM Linux To: Will Deacon Cc: Simon Marchi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: Possible race between PTRACE_SETVFPREGS and PTRACE_CONT on ARM? Message-ID: <20160531141817.GW19428@n2100.arm.linux.org.uk> References: <574C7CDB.7050103@ericsson.com> <20160530213529.GS19428@n2100.arm.linux.org.uk> <20160530224028.GT19428@n2100.arm.linux.org.uk> <20160531135251.GK24936@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160531135251.GK24936@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 31, 2016 at 02:52:52PM +0100, Will Deacon wrote: > The only thing I'm uncertain of is whether or not PTRACE_SEIZE/PTRACE_LISTEN > allow switching to the child (but even then, how is the parent doing > to issue such a request?). I can't see how that would be possible - the parent needs to finish the vfp_set() call before it can issue any others - and there can only be one tracer. IOW, if we're in vfp_set(), the thread must have attached to the child, at which point PTRACE_SEIZE will be rejected. PTRACE_LISTEN also requires the child to be in STOP state as well, and again, can only be issued from the current tracer. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.