From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Guthro Subject: Re: [PATCH] ns16550: delay resume until dom0 ACPI has a chance to run Date: Thu, 17 Jan 2013 07:04:17 -0500 Message-ID: <-7156672500108411140@unknownmsgid> References: <1358367656-5333-1-git-send-email-benjamin.guthro@citrix.com> <20130116212414.GT8912@reaktio.net> <50F71C3F.3040105@citrix.com> <50F71E58.4000004@citrix.com> <50F7EA1102000078000B6BD5@nat28.tlf.novell.com> Mime-Version: 1.0 (1.0) Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50F7EA1102000078000B6BD5@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: Malcolm Crossley , Ben Guthro , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On Jan 17, 2013, at 6:09 AM, Jan Beulich wrote: >>>> On 16.01.13 at 22:48, Ben Guthro wrote: >> On Wed, Jan 16, 2013 at 4:40 PM, Malcolm Crossley >> wrote: >> >>> Do these laptops (T430/T530) have built in serial? >> >> They seem to have the hardware for it, but no actual serial connector >> out of the machine. >> This hardware provides the legacy port that Xen initializes in >> xen/arch/x86/setup.c __start_xen() >> >> When the resume happened, it was getting stuck in __ns16550_poll() >> because it thought that the >> LSR register was 0xFF - and had lots of data to read. It got stuck in >> that while loop, and never >> exited. > > So before acking the patch I'd like to understand how we end up > in that loop even when no serial console is in use. Assuming that's > because the post-IRQ initialization (mostly) unconditionally inserts > the timer, that shouldn't be an issue on -unstable (as post-IRQ > init of the individual drivers doesn't get called anymore when no > respective command line option was present, and likewise their > suspend/resume handlers don't get called anymore in that case). > In which case backporting from -unstable would be preferable > over putting custom stuff on the 4.x branches (albeit we likely > still want the change here to have a way to resume with serial > console, but the impact would be quite different). > > Jan > Admittedly, I have been doing my testing on 4.2.y I can try unstable today to see if it makes a difference in this path.