linux-kernel - Re: [GIT PULL] core/printk changes for v3.1

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Message-ID: <20110726114345.GB3298@swordfish.minsk.epam.com>
Date:	Tue, 26 Jul 2011 14:43:46 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Arnaud Lacombe <lacombar@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	DaveJones <davej@...hat.com>
Subject: Re: [GIT PULL] core/printk changes for v3.1

On (07/26/11 13:28), Peter Zijlstra wrote:
> > > Peter Zijlstra (3):
> > >      [...]
> > >      lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion
> > >
> > This commit is triggering:
> > 
> > WARNING: at /src/linux/linux/kernel/lockdep.c:2529
> 
> Not actually having reproduced the problem, does the below cure things?
>

Hello,
Well, it's not that it happens often on my system. I'll test for 
several hours.

	Sergey

 
> ---
> Subject: lockdep: Fix trace_hardirqs_on_caller()
> From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Date: Tue Jul 26 13:13:44 CEST 2011
> 
> Commit dd4e5d3ac4a ("lockdep: Fix trace_[soft,hard]irqs_[on,off]()
> recursion") made a bit of a mess of the various checks and error
> conditions.
> 
> In particular it moved the check for !irqs_disabled() before the
> spurious enable test, resulting in some warnings.
> 
> Reported-by: Arnaud Lacombe <lacombar@...il.com>
> Reported-by: Dave Jones <davej@...hat.com>
> Reported-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  kernel/lockdep.c |   30 ++++++++++++++++--------------
>  1 file changed, 16 insertions(+), 14 deletions(-)
> Index: linux-2.6/kernel/lockdep.c
> ===================================================================
> --- linux-2.6.orig/kernel/lockdep.c
> +++ linux-2.6/kernel/lockdep.c
> @@ -2485,23 +2485,9 @@ static void __trace_hardirqs_on_caller(u
>  {
>  	struct task_struct *curr = current;
>  
> -	if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
> -		return;
> -
> -	if (unlikely(curr->hardirqs_enabled)) {
> -		/*
> -		 * Neither irq nor preemption are disabled here
> -		 * so this is racy by nature but losing one hit
> -		 * in a stat is not a big deal.
> -		 */
> -		__debug_atomic_inc(redundant_hardirqs_on);
> -		return;
> -	}
>  	/* we'll do an OFF -> ON transition: */
>  	curr->hardirqs_enabled = 1;
>  
> -	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
> -		return;
>  	/*
>  	 * We are going to turn hardirqs on, so set the
>  	 * usage bit for all held locks:
> @@ -2529,9 +2515,25 @@ void trace_hardirqs_on_caller(unsigned l
>  	if (unlikely(!debug_locks || current->lockdep_recursion))
>  		return;
>  
> +	if (unlikely(current->hardirqs_enabled)) {
> +		/*
> +		 * Neither irq nor preemption are disabled here
> +		 * so this is racy by nature but losing one hit
> +		 * in a stat is not a big deal.
> +		 */
> +		__debug_atomic_inc(redundant_hardirqs_on);
> +		return;
> +	}
> +
>  	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
>  		return;
>  
> +	if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
> +		return;
> +
> +	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
> +		return;
> +
>  	current->lockdep_recursion = 1;
>  	__trace_hardirqs_on_caller(ip);
>  	current->lockdep_recursion = 0;
> 
--
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