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

[Petr Mladek <pmladek@suse.com>]

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.

Best Regards,
Petr