Re: [Ksummit-discuss] Late KS topics

[Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>]

On (10/26/15 23:51), Jiri Kosina wrote:
> On Mon, 26 Oct 2015, Hannes Reinecke wrote:
> 
> >   The talk/proposal should be used to come to a consensus about
> >   restricting printk() to high-priority, small volume messages,
> >   and implement a different call (like log_printk()) for the
> >   low-priority, high-volume traffic.
> 
> The printk() troubles are not only about the "high volume" vs. "very 
> important", but also about the context of the caller.

sometimes "high volume" and 'unlucky' printk_deferred() dynamic duo
can do dramatic things. printk_deferred() queues a irq work -
wake_up_klogd_work(), which does

wake_up_klogd_work_func():
	..
	console_trylock()
		console_unlock()


so we eventually end up in

	for (;;) {
		..
		call_console_drivers()
		..
	}

	-ss

> The optimistic comment above printk() says that it can be called from any 
> context, but that's not true for quite some time already.
> So if printk() is going to be redesigned to be more lightweight, this 
> aspect definitely needs to be taken into consideration as well.