Re: [PATCH 16/16] phy: phy-core: fix initcall level

[Alexander Holler]

Am 18.09.2015 um 08:16 schrieb Kishon Vijay Abraham I:
> Hi,
>
> On Wednesday 26 August 2015 05:58 PM, Alexander Holler wrote:
> > The phy-core has to be initialized before other dependent usb-drivers,
> > otherwise a crash might occur.
> >
> > Currently phy_core_init() is called in the initcall-level device, which is
> > the same level where most usb-drivers will end up. By luck this seemed to
> > have been called most of the time before other usb-drivers without having
> > been explicitly enforced. But if phy_core_init() is not called before a
> > dependent driver, a null-pointer exception might occur (e.g. because the
> > phy device class isn't registered).
>
> Did you actually face a problem? IIUC the modules get loaded based on
> the drivers/Makefile order (unless the other modules are in a different
> initcall table).

I had a problem while playing with a modified init-system (based on 
dependencies). So not an actual problem.

> IMHO the fix should be in the module that caused the crash. Change it to
> use module_init?

The problem arises if the init-system ignores the link order and assumes 
all drivers in the same initcall level can be called without any special 
ordering.
The problem might also appear if a driver changes its name, directory or 
position in file system. E.g. how to you make sure that a driver in 
staging will be linked after the phy-core? Actually this happens, but I 
would assume its by luck. I assume if staging would be renamed to 
'beta-quality' a lot of stuff would actually fail because of the problem 
with the implicit link order.

Anyway, nothing which really has to be fixed. It's just a notice that 
maybe another initcall level of 'subsys' or something else before 
'device' might be a better place for phy-core. I've chosen fs_sync 
instead of subsys because otherwise I would have had to look up if 
phy-core depends on another subsystem and therefore has to be 
initialized after subsys.

Regards,

Alexander Holler

> Thanks
> Kishon
>
> > To fix this, phy_core_init() is moved to the initcall-level fs (right
> > before the standard initcall level device).
> >
> > Signed-off-by: Alexander Holler <holler@xxxxxxxxxxxxx>
> > ---
> >   drivers/phy/phy-core.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
> > index fc48fac..4945029 100644
> > --- a/drivers/phy/phy-core.c
> > +++ b/drivers/phy/phy-core.c
> > @@ -930,7 +930,7 @@ static int __init phy_core_init(void)
> >
> >   	return 0;
> >   }
> > -module_init(phy_core_init);
> > +fs_initcall_sync(phy_core_init);
> >
> >   static void __exit phy_core_exit(void)
> >   {
> --
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