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

Petr Mladek
2018-01-11T09:34:43Z

On Thu 2018-01-11 13:58:17, Sergey Senozhatsky wrote:
> On (01/10/18 13:05), Steven Rostedt wrote:
> > The solution is simple, everyone at KS agreed with it, there should be
> > no controversy here.
>
> frankly speaking, that's not what I recall ;)

To be honest, I do not longer remember the details. I think that
nobody was really against that solution. Of course, there were
doubts and other proposals.

I think that I was actually the most sceptical guy there. I would
split my old doubts into three areas:

+ new possible deadlocks
-> I was wrong

+ did not fully prevent softlockups
-> no real life example in hands

+ looked tricky and complex
-> like many other new things

You see that I have changed my mind and decided to give this solution
a chance.

> [..]
> > My printk solution is solid, with no risk of regressions of current
> > printk usages.
>
> except that handing off a console_sem to atomic task when there
> is O(logbuf) > watchdog_thresh is a regression, basically...
> it is what it is.

How this could be a regression? Is not the victim that handles
other printk's random? What protected the atomic task to
handle the other printks before this patch?

Or do you have a system that started to suffer from softlockups
with this patchset and did not do this before?

>
> > If anything, I'll pull theses patches myself, and push them to Linus
> > directly
>
> lovely.

Do you know about any system where this patch made the softlockup
deterministically or statistically more likely, please?

Best Regards,
Petr