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Date: Mon, 15 Jan 2018 07:08:21 -0500
From: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup
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To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>, Tejun Heo <tj@kernel.org>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, 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>, Linus Torvalds <torvalds@linux-foundation.org>, Jan Kara <jack@suse.cz>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, rostedt@home.goodmis.org, Byungchul Park <byungchul.park@lge.com>, Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org

On Fri, 12 Jan 2018 13:55:37 +0100
Petr Mladek <pmladek@suse.com> wrote:

> > I'm not fixing console_unlock(), I'm fixing printk(). BTW, all my
> > kernels are CONFIG_PREEMPT (I'm a RT guy), my mind thinks more about
> > PREEMPT kernels than !PREEMPT ones.  
> 
> I would say that the patch improves also console_unlock() but only in
> non-preemttive context.
> 
> By other words, it makes console_unlock() finite in preemptible context
> (limited by buffer size). It might still be unlimited in
> non-preemtible context.

Since I'm worried most about printk(), I would argue to make printk
console unlock always non-preempt.

	preempt_disable();
	if (console_trylock_spinning())
		console_unlock();
	preempt_enable();

-- Steve

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