Re: [lm-sensors] [PATCH] x86/hwmon: fix module init for hotplug-but-no-device-foundcase

[Chen Gong]

ä 9/14/2010 2:47 PM, Jan Beulich åé:
> > > > On 14.09.10 at 08:30, Chen Gong<gong.chen@xxxxxxxxxxxxxxx>  wrote:
> > ä 9/13/2010 6:05 PM, Jan Beulich åé:
> > > In commit 0dca94baeab4a1a514841b0a4c8e3a51dfb4d5ae the call to
> > > platform_driver_unregister() was made conditional upon !HOTPLUG_CPU,
> > > but the return value from coretemp_init() was left to indicate an
> > > error. This isn't correct, as the negative return value indicates to
> > > the module loader that initialization failed, which isn't intended
> >
> > only !HOTPLUG_CPU can remove the driver. That is what we need to do
> > because under the hotplug condition, we need to consider those "offline"
> > cpus. I don't understand what you are afraid. Can you give me a scinario ?
>
> If the driver's init routine returns -ENODEV (like is the case without this
> change when HOTPLUG_CPU is enabled and there is no device found),
> the platform driver will remain registered, yet the driver memory will
> get freed (leaving dangling pointers into the driver's former image). Or

Under this condition, I can't fine who frees the memory of the platform
driver

> in other words - when leaving the driver registered, the return value
> of the init function must be zero.

Is it mandotary or just some kind of convention ?

> Jan
>
> > > here and results in dangling pointers.
> > >
> > > Signed-off-by: Jan Beulich<jbeulich@xxxxxxxxxx>
> > > Cc: Chen Gong<gong.chen@xxxxxxxxxxxxxxx>
> > >
> > > ---
> > >    drivers/hwmon/coretemp.c |    5 ++++-
> > >    1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > --- linux-2.6.36-rc4/drivers/hwmon/coretemp.c	2010-09-13 08:45:02.000000000
> > +0200
> > > +++
> > 2.6.36-rc4-x86-coretemp-hotplug-init-return/drivers/hwmon/coretemp.c	2010-
> > 09-03 17:54:14.000000000 +0200
> > > @@ -541,16 +541,19 @@ static int __init coretemp_init(void)
> > >    				" has no thermal sensor.\n", c->x86_model);
> > >    		}
> > >    	}
> > > +
> > > +#ifndef CONFIG_HOTPLUG_CPU
> > >    	if (list_empty(&pdev_list)) {
> > >    		err = -ENODEV;
> > >    		goto exit_driver_unreg;
> > >    	}
> > > +#endif
> > >
> > >    	register_hotcpu_notifier(&coretemp_cpu_notifier);
> > >    	return 0;
> > >
> > > -exit_driver_unreg:
> > >    #ifndef CONFIG_HOTPLUG_CPU
> > > +exit_driver_unreg:
> > >    	platform_driver_unregister(&coretemp_driver);
> > >    #endif
> > >    exit:
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