Re: [PATCH] panic: Ensure preemption is disabled during panic()

[Will Deacon]

Hi Andrew,

Thanks for having a look.

On Wed, Oct 02, 2019 at 02:45:58PM -0700, Andrew Morton wrote:
> On Wed,  2 Oct 2019 13:35:38 +0100 Will Deacon <will@xxxxxxxxxx> wrote:
> > Disable preemption in 'panic()' before re-enabling interrupts.
> > 
> > ...
> >
> > --- a/kernel/panic.c
> > +++ b/kernel/panic.c
> > @@ -180,6 +180,7 @@ void panic(const char *fmt, ...)
> >  	 * after setting panic_cpu) from invoking panic() again.
> >  	 */
> >  	local_irq_disable();
> > +	preempt_disable_notrace();
> >  
> >  	/*
> >  	 * It's possible to come here directly from a panic-assertion and
> 
> We still do a lot of stuff (kexec, kgdb, etc) after this
> preempt_disable() and I worry that something in there will now trigger
> a might_sleep() warning as a result?

Given that interrupts are already disabled at this point, I don't think
we'll get any additional warnings here by disabling preemption as well.

Will