Re: [RESEND AGAIN][PATCH] pcmcia: move unbind/rebind intodev_pm_ops.complete

From: Andrew Morton
Date: Mon Jul 09 2012 - 19:01:27 EST


On Tue, 10 Jul 2012 00:54:54 +0200
Christian Lamparter <chunkeey@xxxxxxxxxxxxxx> wrote:

> On Monday, July 09, 2012 11:59:39 PM Andrew Morton wrote:
> > On Fri, 6 Jul 2012 14:30:16 -0700
> > Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > > On Fri, Jul 06, 2012 at 11:23:52PM +0200, Christian Lamparter wrote:
> > > > The idea of moving rebind procedure into pm.complete
> > > > was taken from the usb-subsystem, which has similar
> > > > problems with reattaching devices during/after
> > > > resume.
> > > >
> > > > Signed-off-by: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>
> > > > ---
> > > > To Greg:
> > > >
> > > > I have submitted this patch back in March and again in May.
> > > > As far as I can tell it was neither rejected nor was it
> > > > accepted into linux-pcmcia.git since. So I'm asking you,
> > > > if you could take the patch instead... please.
> > >
> > > There is a PCMCIA "team" who should be taking these types of patches.
> > > Why are they not doing so?
> > >
> >
> > Things are pretty quiet in pcmcia world, but Dominik does appear to
> > still be doing stuff.
> >
> > I sometimes queue PCMCIA patches for people, but not this one. The
> > changelog is just junk. What does the patch do? Why does it do it?
> > What problems does it solve? What are these mysterious "problems with
> > reattaching devices" to which it refers? Useless...
> >
> Well, that can be improved, but it is a bit tricky.
> AFAICT the usb subsystem dealt with pm in this commit:
>
> "commit 5096aedcd2eb70fbea83f09281f97f9ec973d9de
> Author: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Date: Tue Aug 12 14:34:14 2008 -0400
>
> USB: Don't rebind before "complete" callback
>
> [...] We are not allowed to call drivers' probe routines during
> a system sleep transition between the "prepare" and "complete"
> callbacks, but that's exactly what we do when a driver doesn't
> have full suspend/resume support. [...]"
>
> And on the pcmcia subsystem we have this:
>
> "commit 88b060d6c03fcb9e4d2018b4349954c4242a5c7f
> Author: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
> Date: Sat Jan 2 14:14:23 2010 +0100
>
> pcmcia: improve check for same card in slot after resume
>
> During a suspend/resume cycle, an user may change the card in the
> PCMCIA/CardBus slot. [...]
>
> For CardBus devices, the PCI hotplug interface doesn't offer a "rescan"
> facility which also _removes_ devices no longer to be found behind a
> bridge. Therefore, remove and re-add all devices unconditionally."
>
> Unfortunately, the "re-add" is currently done in the *pm resume* callback
> (socket_late_resume), but according to "USB: Don't rebind..." is not
> allowed to have it there, so the patch moves it into the *pm complete*
> callback. The Documentation/power/* contains mostly informations for
> drivers developers, but AFAICT it doesn't say much about the subsystem
> to which the device is connected should behave, so there's a bit of a
> "citing-gap".

hm, it does seem a bit of a screwup.

What's unclear to me is whether your patch fixes any observed runtime
problems. Or adds any runtime problems, which looks to be a distinct
possibility.

> So, my question now: Would you accept the pcmcia patch if I add the
> "USB: Don't rebind..." as a reference to why the re-add needs to be
> done in complete? Or do you think that I should bug the pm people
> (and Alan - since he wrote that it is "not allowed") in this case
> so I can link their official answer to this patch?

Well I could grab it and give it a little bit of testing in linux-next.
But I'd be super-reluctant to send such a patch upstream without
detailed input from Alan/Greg/Rafael/Dominik/etc.

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