Messages in this thread | | | Date | Sun, 17 Feb 2013 20:31:52 +0900 | From | Alex Courbot <> | Subject | Re: usb_wwan_write() called while device still being resumed |
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On 02/15/2013 08:05 PM, Bjørn Mork wrote: > Alex Courbot <acourbot@nvidia.com> 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. -- 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/
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