Re: Driver bind/unbind and __devinit

[Dmitry Torokhov]

On 12/8/05, Greg KH <gregkh@xxxxxxx> wrote:
> On Thu, Dec 08, 2005 at 05:22:12PM -0500, Dmitry Torokhov wrote:
> > On 12/8/05, Greg KH <gregkh@xxxxxxx> wrote:
> > > On Thu, Dec 08, 2005 at 04:14:58PM -0500, Dmitry Torokhov wrote:
> > > > Hi,
> > > >
> > > > Many drivers have their probe routines declared as __devinit which is
> > > > a no-op unless CONFIG_HOTPLUG is set. However driver's bind/unbind
> > > > attributes are created unconditionally, as fas as I can see. Would not
> > > > it cause an oops if someone tries to use these attributes with
> > > > CONFIG_HOTPLUG=N? Am I missing something?
> > >
> > > You are missing the CONFIG_HOTPLUG checks around the functions that add
> > > and check the device ids from these sysfs files.  If CONFIG_HOTPLUG is
> > > not enabled, those files do not do anything.
> > >
> >
> > I am slow today... I don't see any dependencies on CONFIG_HOTPLUG in
> > drivers/base... Or you talking about one particular subsystem that
> > handles this correctly?
>
> Ugh, very sorry about that, I was thinking of the USB and PCI new_id
> stuff.  You are right.
>
> Yes, bind happening after the __init data section is thrown away, if
> CONFIG_HOTPLUG is not enabled would be a bad thing.  But unbind can
> stay.  I'll go make up a patch for that.
>

Unbind may invoke ->remove code which is __devexit[_p] and may be also
discarded if !MODULE && !HOTPLUG.

> > > > Also, unbind implementation does not seem safe - we check the driver
> > > > before taking device's semaphore so we risk unbinding wrong driver (in
> > > > the unlikely event that we manage to unbind and bind another driver in
> > > > another thread).
> > >
> > > Do you have a suggestion as to how to fix this?
> > >
> >
> > I think we could take the semaphore before checking driver and then
> > use __device_release_driver(). But we'd need to make it global or move
> > bind/unbind code into drivers/base/dd.c
>
> I don't have a problem moving the code if it makes it easier.  Have a
> patch?  :)
>

Just handwaving for now ;)

--
Dmitry
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