Re: netconsole: HARDIRQ-safe -> HARDIRQ-unsafe lock order warning

[John Ogness <john.ogness@linutronix.de>]

On 2025-09-06, Mike Galbraith <efault@gmx.de> wrote:
>> The ->write_atomic() callback is intended to perform immediate
>> transmission. It is called with hardware interrupts disabled and is even
>> expected to work from NMI context. If you are not able to implement
>> these requirements, do not implement ->write_atomic(). Implementing some
>> sort of deferrment mechanism is inappropriate. Such a mechanism already
>> exists based on ->write_thread().
>
> Truly atomic packet blasting would be a case of happiness, but barring
> that, deferment is way better than the nothing that's available to both
> RT and !RT+wireless here/now.  With a .write_atomic that's really just
> .write_thread, both RT and !RT+wireless managed to successfully send a
> death rattle with the WIP nbcon patch.. a progression for each of them.

Just be aware that ->write_atomic() will be called from _any_ context
(including scheduler and NMI) and a console implementing this callback
must handle the message or the message is lost for that console.

I request that I am added CC to the next incarnation of this
series. Thanks!

John Ogness