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Date: Tue, 16 Jan 2018 14:23:01 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Tejun Heo <tj@kernel.org>, akpm@linux-foundation.org,
        linux-mm@kvack.org, Cong Wang <xiyou.wangcong@gmail.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Peter Zijlstra <peterz@infradead.org>,
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        rostedt@home.goodmis.org, Byungchul Park <byungchul.park@lge.com>,
        Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup
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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