Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup

Sergey Senozhatsky
2018-01-16T05:23:07Z

Hi,

On (01/15/18 11:17), Petr Mladek wrote:
> Hi Sergey,
>
> I wonder if there is still some miss understanding.
>
> Steven and me are trying to get this patch in because we believe
> that it is a step forward. We know that it is not perfect. But
> we believe that it makes things better. In particular, it limits
> the time spent in console_unlock() in atomic context. It does
> not make it worse in preemptible context.
>
> It does not block further improvements, including offloading
> to the kthread. We will happily discuss and review further
> improvements, it they prove to be necessary.
>
> The advantage of this approach is that it is incremental. It should
> be easier for review and analyzing possible regressions.
>
> What is the aim of your mails, please?
> Do you want to say that this patch might cause regressions?
> Or do you want to say that it does not solve all scenarios?
>
> Please, answer the above questions. I am still confused.

I ACK-ed the patch set, given that I hope that we at least will
do (a)

a) remove preemption out of printk()->user critical path

---

b) the next thing would be - O(logbuf) is not a good boundary

c) the thing after that would be to - O(logbuf) boundary can be
broken in both preemptible and non-preemptible contexts.

but (b) and (c) can wait.

-ss