improve printk reliability [LWN.net]

From:		Peter Zijlstra <a.p.zijlstra@chello.nl>
To:		Linus Torvalds <torvalds@linux-foundation.org>, Ted Ts'o <tytso@mit.edu>, Greg KH <greg@kroah.com>, Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>, akpm@linux-foundation.org
Subject:		[RFC][PATCH 0/7] improve printk reliability
Date:		Wed, 21 Dec 2011 11:57:39 +0100
Message-ID:		<20111221105739.798864333@chello.nl>
Cc:		linux-kernel <linux-kernel@vger.kernel.org>
Archive-link:		Article, Thread

Hi,

So these are my current efforts to make my own console output more
reliable. I've hit every deadlock described in this series and a few
more.

With these patches applied I can printk() and WARN() from inside 
scheduler context and not have my machine deadlock, even without the 
aid of early_printk().

While I'll go an remove the sole printk() I found in the scheduler
so that we don't have to rely on the console doing this, it is good
to have a reliable console that can do this.

As it stands some of the patches, the semaphore one in particular,
are really too ugly to live so I won't push those but wanted to share
anyway.

Debugging this was 'fun', and I really hope to not have to do it
again :-)

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