Re: [PATCH net] netpoll: run NAPI poll in softirq context to avoid rq->lock self-deadlock

[Peter Zijlstra <peterz@infradead.org>]

On Wed, Jun 17, 2026 at 12:12:07PM +0200, Petr Mladek wrote:
> On Tue 2026-06-16 17:31:22, Sebastian Andrzej Siewior wrote:
> > On 2026-06-16 08:11:28 [-0700], Jakub Kicinski wrote:
> > > > 
> > > > Adding sched and printk folks for opinions while eyeballing
> > > > WARN_ON_DEFERRED().
> > > 
> > > Thanks a lot for looking into this! To be clear - the printk_deferred /
> > > WARN_DEFERRED would be just for stable? Or there's still some
> > > sensitivity even with nbcon?
> > 
> > We already have printk_deferred(). WARN_DEFERRED() would be new. I
> > *think* this is not limited netpoll/ netconsole but all console drivers
> > not using CON_NBCON if the printk (via WARN) occurs with the rq held.
> > I don't remember all the details but printk_deferred() was introduced to
> > circumvent this until printk is fixed.
> 
> Just to make it clear. The problem with the legacy consoles is that
> they are called under console_lock() which is a semaphore. And it
> calls wake_up_process() in console_unlock() when there is another
> waiter on the lock.
> 
> > Once we get rid of those legacy drivers and NBCON is the default we can
> > get rid of printk_deferred() :)
> 
> Yup.

Can't we push all the legacy consoles into a single legacy kthread? I
mean, converting all consoles is of course awesome, but should we really
wait for that?