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Date:   Thu, 18 Jan 2018 23:03:24 +0100
From:   Pavel Machek <pavel@ucw.cz>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Petr Mladek <pmladek@suse.com>,
        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>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/2] printk: Add console owner and waiter logic to
 load balance console writes
Message-ID: <20180118220323.GC17196@amd>
References: <20180110132418.7080-1-pmladek@suse.com>
 <20180110132418.7080-2-pmladek@suse.com>
 <20180112115454.17c03c8f@gandalf.local.home>
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Hi!

> > By other words, this deadlock was there even before. Such
> > deadlocks are prevented by using printk_deferred() in
> > the sections guarded by the lock A.
>=20
> Petr,
>=20
> Please add this here:
>=20
> =3D=3D=3D=3D
>=20
> To demonstrate the issue, this module has been shown to lock up a
> system with 4 CPUs and a slow console (like a serial console). It is
> also able to lock up a 8 CPU system with only a fast (VGA) console, by
> passing in "loops=3D100". The changes in this commit prevent this module
> from locking up the system.
>=20
> #include <linux/module.h>
> #include <linux/delay.h>
> #include <linux/sched.h>
> #include <linux/mutex.h>
> #include <linux/workqueue.h>
> #include <linux/hrtimer.h>

Programs in commit messages. Not preffered way to distribute code, I'd
say. What about putting it into kernel selftests directory or
something like that?
									Pavel

--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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