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

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Date:	Mon, 06 Jun 2011 15:12:08 +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 Mon, 2011-06-06 at 15:10 +0200, Ingo Molnar wrote:


> diff --git a/kernel/printk.c b/kernel/printk.c
> index 3518539..1b9d2be 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -859,7 +859,6 @@ asmlinkage int vprintk(const char *fmt, va_list args)
>  		zap_locks();
>  	}
>  
> -	lockdep_off();

At the very least you should also do: s/raw_local_irq_/local_irq/ on
this function.

>  	spin_lock(&logbuf_lock);
>  	printk_cpu = this_cpu;
>  
> @@ -947,7 +946,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
>  	 * Try to acquire and then immediately release the
>  	 * console semaphore. The release will do all the
>  	 * actual magic (print out buffers, wake up klogd,
> -	 * etc). 
> +	 * etc).
>  	 *
>  	 * The console_trylock_for_printk() function
>  	 * will release 'logbuf_lock' regardless of whether it
> @@ -956,7 +955,6 @@ asmlinkage int vprintk(const char *fmt, va_list args)
>  	if (console_trylock_for_printk(this_cpu))
>  		console_unlock();
>  
> -	lockdep_on();
>  out_restore_irqs:
>  	raw_local_irq_restore(flags);
>  

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