Re: [RFC][PATCHv3 2/5] printk: introduce printing kernel thread

From: Sergey Senozhatsky
Date: Tue Jul 04 2017 - 02:53:54 EST

On (07/04/17 14:26), Sergey Senozhatsky wrote:
> not sure if we can properly throttle printk in all of the cases.
> we know that console_sem is locked, but we don't know what for.
> is CPU that owns the console_sem is now in console_unlock() or
> somewhere in fbcon, or anywhere else. we probably need not to
> throttle printk() if we know that console_sem is already locked
> by this_cpu and we simply call printk either from IRQ that
> preempted console_unlock() on this_cpu or recursive printk from
> console_unlock()... and so on.

which is hard to do, given that console_unlock() can schedule with
console_sem locked. so CPU number won't do the trick. unless we will
forbid preemption in console_unlock()... we sort of need to do it.