Re: [PATCH] PCI: keystone: fix incorrect annotations on probe and remove

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Bjorn,

On Fri, Jan 23, 2015 at 03:34:12PM -0600, Bjorn Helgaas wrote:
> [+cc Fabio]
> 
> On Thu, Jan 08, 2015 at 02:17:36PM -0800, Dmitry Torokhov wrote:
> > Even though platform bus is not hot-pluggable, devices on it can be unbound
> > from the driver and bound back to it via sysfs, so we should not be using
> > __init annotations on probe() and __exit annotations on remove() methods.
> 
> I don't completely understand this problem.  Does this mean there should be
> no __init/__exit annotations in these drivers at all?  If other PCI host
> bridge drivers have the same problem, I'd like to fix them all at once.

Basically they should not use __init/__exit, unless you take explicit
steps to make sure that devices can't be unbound and bound again later
via sysfs by setting driver->suppress_bind_attrs and/or using
platform_driver_probe(). Note that if you use platform_driver_probe()
then your driver can't cope with -EPROBE_DEFER reported by any of the
subsystems it might be using.

> 
> For example, after applying this patch, ks_pcie_probe() is non-__init, but
> it calls ks_add_pcie_port(), which is still __init.  I thought that was
> illegal.

My bad, I missed that. The __init marking on ks_add_pcie_port() shoudl
be removed as well.

> 
> I'm not sure about module_platform_driver_probe() either; it generates
> __init and __exit functions.  Should those annotations be removed, too?

module_platform_driver_probe() does internally platform_driver_probe()
so it is OK for that probe function be __init (because we'd suppress
sysfs bind/unbind and deferred probing so discaring init section is
safe).

Note that above applied to driver's ->probe() and ->remove() code paths
only.  Marking module init/exit code as __init and __exit is still right
thing to do.

Thanks.

> 
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > ---
> > 
> > Not tested, found by casual code inspection.
> > 
> >  drivers/pci/host/pci-keystone.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/host/pci-keystone.c b/drivers/pci/host/pci-keystone.c
> > index 1b893bc..7b84e1d 100644
> > --- a/drivers/pci/host/pci-keystone.c
> > +++ b/drivers/pci/host/pci-keystone.c
> > @@ -332,7 +332,7 @@ static const struct of_device_id ks_pcie_of_match[] = {
> >  };
> >  MODULE_DEVICE_TABLE(of, ks_pcie_of_match);
> >  
> > -static int __exit ks_pcie_remove(struct platform_device *pdev)
> > +static int ks_pcie_remove(struct platform_device *pdev)
> >  {
> >  	struct keystone_pcie *ks_pcie = platform_get_drvdata(pdev);
> >  
> > @@ -341,7 +341,7 @@ static int __exit ks_pcie_remove(struct platform_device *pdev)
> >  	return 0;
> >  }
> >  
> > -static int __init ks_pcie_probe(struct platform_device *pdev)
> > +static int ks_pcie_probe(struct platform_device *pdev)
> >  {
> >  	struct device *dev = &pdev->dev;
> >  	struct keystone_pcie *ks_pcie;
> > @@ -398,9 +398,9 @@ fail_clk:
> >  	return ret;
> >  }
> >  
> > -static struct platform_driver ks_pcie_driver __refdata = {
> > +static struct platform_driver ks_pcie_driver = {
> >  	.probe  = ks_pcie_probe,
> > -	.remove = __exit_p(ks_pcie_remove),
> > +	.remove = ks_pcie_remove,
> >  	.driver = {
> >  		.name	= "keystone-pcie",
> >  		.owner	= THIS_MODULE,
> > -- 
> > 2.2.0.rc0.207.ga3a616c
> > 
> > 
> > -- 
> > Dmitry

-- 
Dmitry