lkml.org 
[lkml]   [2007]   [Apr]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 7/7] [RFC] APM emulation driver for class batteries
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

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-04-20 10:31    [from the cache]
©2003-2011 Jasper Spaans. Advertise on this site