linux-kernel - Re: [PATCH v12 0/3] printk: Make printk() completely async

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Date:	Tue, 12 Jul 2016 10:04:59 -0700
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.com>, Tejun Heo <tj@...nel.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Byungchul Park <byungchul.park@....com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH v12 0/3] printk: Make printk() completely async

On 12-07-16, 17:59, Petr Mladek wrote:
> On Mon 2016-07-11 12:25:11, Viresh Kumar wrote:
> > We were also screwed because of the problem this thread is trying to solve,
> > which I posted last week [1].
> > 
> > And then I found this thread which fixed my issue, thanks a lot guys :)
> > 
> > Tested-by: Viresh Kumar <viresh.kumar@...aro.org>
> > 
> > Though, I would also like to mention one unwanted thing that happened on
> > my setup :)
> > 
> > [   12.874909] sched: RT throttling activated for rt_rq ffffffc0ac13fcd0 (cpu 0)
> > [   12.874909] potential CPU hogs:
> > [   12.874909]  printk (292)
> > 
> > On my system, the excessive printing happens during suspend/resume and this
> > happened after all the non-boot CPUs were offlined. So, only CPU 0 was left and
> > that was doing printing for a long time and so these errors :)
> > 
> > It resulted in missing some print messages eventually as the scheduler probably
> > didn't schedule this thread for sometime after that.
> > 
> > Will it be fine to get the priority of this kthread to a somewhat lower value,
> > etc ?
> 
> I think that this patch helped only by chance.

Sorry got confused a bit here..

Which patch are you taking about here ? As you replied below my
message, I believe that you are talking about the 3 patches that were
posted in this series. But the rest of your comment looks like the
fourth fixup patch that Sergey shared :)

So, the fixup patch doesn't fix any issues in my case, to make it
clear. I still have my system hanging somewhere.

> I am still scratching my head about the problem fixed by this patch
> and also about suspend problems.

:)

-- 
viresh