From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755904Ab3BQL3P (ORCPT ); Sun, 17 Feb 2013 06:29:15 -0500 Received: from hqemgate03.nvidia.com ([216.228.121.140]:2704 "EHLO hqemgate03.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754164Ab3BQL3N convert rfc822-to-8bit (ORCPT ); Sun, 17 Feb 2013 06:29:13 -0500 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Sun, 17 Feb 2013 03:28:34 -0800 Message-ID: <5120BFA8.2000506@nvidia.com> Date: Sun, 17 Feb 2013 20:31:52 +0900 From: Alex Courbot Organization: NVIDIA User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130109 Thunderbird/17.0.2 MIME-Version: 1.0 To: =?UTF-8?B?QmrDuHJuIE1vcms=?= CC: USB list , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Alexandre Courbot Subject: Re: usb_wwan_write() called while device still being resumed References: <511CBCE8.9070204@nvidia.com> <87ehgivlmg.fsf@nemi.mork.no> <511DF09F.3070401@nvidia.com> <87r4khu9az.fsf@nemi.mork.no> In-Reply-To: <87r4khu9az.fsf@nemi.mork.no> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/15/2013 08:05 PM, Bjørn Mork wrote: > Alex Courbot writes: > >> Unfortunately it does not, and fails the same way. On the other hand, >> I do not see the issue when doing the following: >> >> diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c >> index e4fad5e..1490029 100644 >> --- a/drivers/usb/serial/usb_wwan.c >> +++ b/drivers/usb/serial/usb_wwan.c >> @@ -238,8 +238,6 @@ int usb_wwan_write(struct tty_struct *tty, struct >> usb_serial_port *port, >> usb_pipeendpoint(this_urb->pipe), i); >> >> err = >> usb_autopm_get_interface_async(port->serial->interface); >> - if (err < 0) >> - break; >> >> /* send the data */ >> memcpy(this_urb->transfer_buffer, buf, todo); >> >> After doing this I don't see this issue anymore. It looks wrong >> though. But it seems to work despite the obvious unbalance in autopm >> calls that results. >> >> If I understand you correctly, usb_wwan_write() failing here is not a >> problem in itself, and the ack should just be sent again later? > > That was what I thought looking (obviously too) briefly through this. > > Most errors from usb_autopm_get_interface_async will be translated to > EIO before being returned by serial_write. I believe the userspace > application should deal with that. But maybe it just gives up? Should > we return EAGAIN or something instead? > > I don't know. I am pretty clueless about these things... Obviously not as much as I am. :) Checking what userspace is doing could indeed be another trail. > But looking again, trying to guess why it works fine if you just ignore > the error. I believe that is because you then end up hitting this until > the interface is fully resumed: > > if (intfdata->suspended) { > usb_anchor_urb(this_urb, &portdata->delayed); > spin_unlock_irqrestore(&intfdata->susp_lock, flags); > } Yes, this seems to be exactly what is happening. > I am way out of my league here, but I wonder if pm_runtime_get() > shouldn't return -EINPROGRESS instead if there is a queued resume > request or an ongoing resume, regardless of disable_depth? > > Maybe something like the completely untested: > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > index 3148b10..38e19ba 100644 > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -512,6 +512,9 @@ static int rpm_resume(struct device *dev, int rpmflags) > else if (dev->power.disable_depth == 1 && dev->power.is_suspended > && dev->power.runtime_status == RPM_ACTIVE) > retval = 1; > + else if (rpmflags & RPM_ASYNC && dev->power.request_pending && > + dev->power.request == RPM_REQ_RESUME) > + retval = -EINPROGRESS; > else if (dev->power.disable_depth > 0) > retval = -EACCES; > if (retval) > --- > usb_autopm_get_interface_async() will interprete EINPROGRESS as success, > so that would prevent this problem. That sounds sensefull indeed. If the interface is soon to be resumed, there should be no reason for usb_autopm_get_interface_async() to fail. Let's give this a try and bring the idea to the PM people if it works. In any case thanks a lot for the help, it is extremely useful. Alex.