Re: [PATCH v1 1/3] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")

[David Hildenbrand]

On 26.09.22 09:44, Kalle Valo wrote:
> David Hildenbrand <david@xxxxxxxxxx> writes:
>
> > > > +Use WARN_ON_ONCE() rather than WARN() or WARN_ON()
> > > > +**************************************************
> > > > +
> > > > +WARN_ON_ONCE() is generally preferred over WARN() or WARN_ON(), because it
> > > > +is common for a given warning condition, if it occurs at all, to occur
> > > > +multiple times. This can fill up and wrap the kernel log, and can even slow
> > > > +the system enough that the excessive logging turns into its own, additional
> > > > +problem.
> > >
> > > FWIW I have had cases where WARN() messages caused a reboot, maybe
> > > mention that here? In my case the logging was so excessive that the
> > > watchdog wasn't updated and in the end the device was forcefully
> > > rebooted.
> >
> > That should be covered by the last part, no? What would be your suggestion?
>
> I was just thinking that maybe make it more obvious that even WARN_ON()
> can crash the system, something along these lines:
>
> "..., additional problem like stalling the system so much that it causes
> a reboot."

Hi Kalle,

sorry for the late reply. Jonathan already queued v2 and sent it upstream.

I think that's it is already covered by the statement and that the 
additional example isn't required -- most of us learned the hard way 
that "excessive logging turns into its own problem" includes all weird 
kinds of kernel crashes. A panic/reboot due to a watchdog not firing is 
one such possible outcome.

Thanks!

--
Thanks,

David / dhildenb