Re: [PATCH 7/7] [RFC] APM emulation driver for class batteries

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > +static void (*old_apm_get_power_status)(struct apm_power_info*);
> > > +
> > > +static int __init apm_battery_init(void)
> > > +{
> > > +	printk(KERN_INFO "APM Battery Driver\n");
> > > +
> > > +	old_apm_get_power_status = apm_get_power_status;
> > > +	apm_get_power_status = apm_battery_apm_get_power_status;
> > > +	return 0;
> > > +}
> > > +
> > > +static void __exit apm_battery_exit(void)
> > > +{
> > > +	apm_get_power_status = old_apm_get_power_status;
> > > +	return;
> > > +}
> > 
> > Utterly unsafe.  What happens if some other module gets loaded which
> > does this, and then this module is unloaded followed by the other
> > module.  Result: Oops.
> 
> Right. And loading two modules which changing apm_get_power_status
> is a race already. Thus, APM interface needs a mutex.
> 
> Or pda_power should be marked "bool" in Kconfig, as it is done
> in arch/arm/common/sharpsl_pm.c. Sharpsl_pm is safe only because it
> can't be a module.

Just mark it bool, when you fix it with mutex, you can go back to
tristate.
								Pavel

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