linux-kernel - Re: [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages

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Date:	Wed, 08 Jun 2011 21:45:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Arne Jansen <lists@...-jansens.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	efault@....de, npiggin@...nel.dk, akpm@...ux-foundation.org,
	frank.rowand@...sony.com, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [debug patch] printk: Add a printk killswitch to robustify NMI
 watchdog messages

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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