disabling timer interrupt until (system_state >= SYSTEM_RUNNING)

[William Tambe]

On Thu, Feb 6, 2020 at 2:24 PM Greg KH <greg at kroah.com> wrote:
>
> On Thu, Feb 06, 2020 at 12:25:27PM -0500, William Tambe wrote:
> > Since voluntary preemption is used during kernel booting, is it safe
> > to disable timer interrupt until (system_state >= SYSTEM_RUNNING) ?
> >
> > Wouldn't it speed up booting ?
>
> Try it and see!
>
> :)
>
> Seriously, think about what needs to be done by the system during boot
> time.  Hardware is initialized, threads are spawned, lots of other
> things are going on.  It's not just one single process until that system
> state change happens by any means.

I am doing kernel porting work and I am able to see Linux booting all
the way to init without timer interrupt; despite kernel thread being
spawned during booting.

Perhaps I may start seeing issues if a module spawn a thread that
never voluntarily preempt itself ?

>
> thanks,
>
> greg k-h