Subject: Re: [debug patch] printk: Add a printk killswitch to robustify NMI
 watchdog messages
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Arne Jansen <lists@die-jansens.de>,
        Linus Torvalds <torvalds@linux-foundation.org>, mingo@redhat.com,
        hpa@zytor.com, linux-kernel@vger.kernel.org, efault@gmx.de,
        npiggin@kernel.dk, akpm@linux-foundation.org, frank.rowand@am.sony.com,
        tglx@linutronix.de, linux-tip-commits@vger.kernel.org
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Date: Wed, 08 Jun 2011 21:45:29 +0200
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On Wed, 2011-06-08 at 21:17 +0200, Ingo Molnar wrote:
> Hm, the no-wakeup aspect seems rather useful.
> 
> Could we perhaps remove console_sem and replace it with a mutex and 
> do something like this with a mutex and its ->wait_lock?
> 
> We'd have two happy side effects:
> 
>  - we'd thus remove one of the last core kernel semaphore users
>  - we'd gain lockdep coverage for console locking as a bonus ... 

The mutex thing is more complex due to the mutex fast path, the
advantage of the semaphore is its simple implementation that always
takes the internal lock.

I guess I can make it happen, but its a tad more tricky.
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