Re: [PATCH v4 1/7] kernel: Add support for restart notifier call chain

[Guenter Roeck]

On 07/14/2014 07:53 AM, Catalin Marinas wrote:
> On Sun, Jul 13, 2014 at 04:30:25PM +0100, Guenter Roeck wrote:
> > diff --git a/include/linux/reboot.h b/include/linux/reboot.h
> > index 48bf152..120db73 100644
> > --- a/include/linux/reboot.h
> > +++ b/include/linux/reboot.h
> > @@ -38,6 +38,9 @@ extern int reboot_force;
> >   extern int register_reboot_notifier(struct notifier_block *);
> >   extern int unregister_reboot_notifier(struct notifier_block *);
> >
> > +extern int register_restart_notifier(struct notifier_block *);
> > +extern int unregister_restart_notifier(struct notifier_block *);
> > +extern void kernel_restart_notify(char *cmd);
> >
> >   /*
> >    * Architecture-specific implementations of sys_reboot commands.
> > diff --git a/kernel/reboot.c b/kernel/reboot.c
> > index a3a9e24..1bc9bf2 100644
> > --- a/kernel/reboot.c
> > +++ b/kernel/reboot.c
> > @@ -104,6 +104,87 @@ int unregister_reboot_notifier(struct notifier_block *nb)
> >   }
> >   EXPORT_SYMBOL(unregister_reboot_notifier);
> >
> > +/*
> > + *	Notifier list for kernel code which wants to be called
> > + *	to restart the system.
> > + */
> > +static BLOCKING_NOTIFIER_HEAD(restart_notifier_list);
> > +
> > +/**
> > + *	register_restart_notifier - Register function to be called to reset
> > + *				    the system
> > + *	@nb: Info about notifier function to be called
> > + *	@nb->priority:	Notifier priority. Notifiers should follow the
> > + *			following guidelines for setting priorities.
> > + *			0:	Restart notifier of last resort,
> > + *				with limited restart capabilities
> > + *			128:	Default notifier; use if no other
> > + *				notifier is expected to be available,
> > + *				and/or if restart functionality is
> > + *				sufficient to restart the entire system
> > + *			255:	Highest priority notifier, will preempt
> > + *				all other notifier functions
>
> I'm not fully convinced implying a 'notifier' is the right approach
> here. By analogy with the reboot notifier, this is something drivers
> would want to know about and do some work before the actual system
> restart (e.g. disable watchdogs as in the reboot notifier case). The
> restart notifier here is meant to perform the actual system restart.
> Arguably, the actual restart should be handled by priority 0 with some
> preparation before but we have reboot notifier already, so I don't think
> it's worth another notifier.
>
> While re-using the notifier mechanism behind the scene is fine, I think
> we should at least rename the functions to something like
> (un)register_restart_handler().

Fine with me. Any other comments / suggestions on the name of the function ?

Guenter


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