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Date:   Sat, 13 Jan 2018 16:31:00 +0900
From:   Sergey Senozhatsky <>
To:     Petr Mladek <>
Cc:     Steven Rostedt <>,
        Sergey Senozhatsky <>,
        Tejun Heo <>,
        Sergey Senozhatsky <>,,,
        Cong Wang <>,
        Dave Hansen <>,
        Johannes Weiner <>,
        Mel Gorman <>, Michal Hocko <>,
        Vlastimil Babka <>,
        Peter Zijlstra <>,
        Linus Torvalds <>,
        Jan Kara <>,
        Mathieu Desnoyers <>,
        Tetsuo Handa <>,, Byungchul Park <>,
        Pavel Machek <>,
Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup

On (01/12/18 13:55), Petr Mladek 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.

could you elaborate a bit?

> > > reverting 6b97a20d3a7909daa06625d4440c2c52d7bf08d7 may be the right
> > > thing after all.
> > 
> > I would analyze that more before doing so. Because with my patch, I
> > think we make those that can do long prints (without triggering a
> > watchdog), the ones most likely doing the long prints.
> IMHO, it might make sense because it would help to see the messages
> faster. But I would prefer to handle this separately because it
> might also increase the risk of softlockups. Therefore it might
> cause regressions.
> We should also take into account the commit 8d91f8b15361dfb438ab6
> ("printk: do cond_resched() between lines while outputting to
> consoles"). It has the same effect for console_lock() callers.

I replied in another email.


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