Re: [PATCH 3/7] Celleb: Support for Power/Reset buttons

[Arnd Bergmann <arnd@arndb.de>]

On Sunday 30 September 2007, you wrote:
>=20
> > kernel_restart() seems appropriate for that.
>=20
> Now a comment to this one says:
>=20
> =A0*=A0=A0=A0=A0=A0=A0This is not safe to call in interrupt context.
>=20
> and AFAIU, this is called from an interrupt. Am I missing anything or=20
> would this be wrong to call kernel_restart() here?

It should be called through a workqueue, afaics, do avoid calling
a sleeping notifier from an interrupt.

> > > +static irqreturn_t beat_reset_event(int virq, void *arg)
> > > +{
> > > +=A0=A0=A0printk(KERN_DEBUG "Beat: reset button pressed\n");
> > > +=A0=A0=A0beat_pm_poweroff_flag =3D 0;
> > > +=A0=A0=A0if (kill_cad_pid(SIGINT, 1)) {
> > > +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0/* Just in case killing init proces=
s failed */
> > > +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0beat_restart(NULL);
> > > +=A0=A0=A0}
> > > +=A0=A0=A0return IRQ_HANDLED;
> > > +}
> >=20
> > same here, except calling kernel_halt() in the end.
>=20
> kernel_halt() doesn't have a similar comment, but it does call the=20
> kernel_shutdown_prepare() too, so, seems like it should not be called fro=
m=20
> an interrupt either?

yes

> Now, another question, is it generally good to hard-wire "reset" and=20
> "power-off" buttons in the kernel? Isn't it better to just register them=
=20
> as input event sources and let userspace (power-management daemon) decide=
=20
> what to do with them? Like poweroff / reboot / suspend / hibernate / ...

Tough question. I can see arguments for either way, but I guess I'd tend
to handling it in the kernel, choosing simplicity over consistency.

	Arnd <><