linux-kernel - Re: [PATCH 2/2] lockdep reentrancy

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Date:	Tue, 23 Jan 2007 20:29:09 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, ltt-dev@...fik.org,
	"Martin J. Bligh" <mbligh@...igh.org>,
	Douglas Niehaus <niehaus@...s.ku.edu>,
	systemtap@...rces.redhat.com, Thomas Gleixner <tglx@...utronix.de>,
	Richard J Moore <richardj_moore@...ibm.com>
Subject: Re: [PATCH 2/2] lockdep reentrancy

On Tue, 16 Jan 2007 12:56:31 -0500
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:

> Here is a patch to lockdep.c so it behaves correctly when a kprobe breakpoint is
> put on a marker within hardirq tracing functions as long as the marker is within
> the lockdep_recursion incremented boundaries. It should apply on 
> 2.6.20-rc4-git3.
> 
> Mathieu
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> 
> 
> @@ -1841,33 +1843,36 @@ void trace_hardirqs_on(void)

You lost the patch headers.

>  	struct task_struct *curr = current;
>  	unsigned long ip;
>  
>  	if (unlikely(!debug_locks || current->lockdep_recursion))
>  		return;
>  
> +	current->lockdep_recursion++;
> +	barrier();

Why can't we use lockdep_off() here?

>  	if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
> -		return;
> +		goto end;
>  
>  	if (unlikely(curr->hardirqs_enabled)) {
>  		debug_atomic_inc(&redundant_hardirqs_on);
> -		return;
> +		goto end;
>  	}
>  	/* we'll do an OFF -> ON transition: */
>  	curr->hardirqs_enabled = 1;
>  	ip = (unsigned long) __builtin_return_address(0);
>  
>  	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
> -		return;
> +		goto end;
>  	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
> -		return;
> +		goto end;
>  	/*
>  	 * We are going to turn hardirqs on, so set the
>  	 * usage bit for all held locks:
>  	 */
>  	if (!mark_held_locks(curr, 1, ip))
> -		return;
> +		goto end;
>  	/*
>  	 * If we have softirqs enabled, then set the usage
>  	 * bit for all held locks. (disabled hardirqs prevented
> @@ -1875,11 +1880,14 @@ void trace_hardirqs_on(void)
>  	 */
>  	if (curr->softirqs_enabled)
>  		if (!mark_held_locks(curr, 0, ip))
> -			return;
> +			goto end;
>  
>  	curr->hardirq_enable_ip = ip;
>  	curr->hardirq_enable_event = ++curr->irq_events;
>  	debug_atomic_inc(&hardirqs_on_events);
> +end:
> +	barrier();
> +	current->lockdep_recursion--;

lockdep_on()?

>  }
>  
>  EXPORT_SYMBOL(trace_hardirqs_on);
> @@ -1888,14 +1896,17 @@ void trace_hardirqs_off(void)
>  {
>  	struct task_struct *curr = current;
>  
>  	if (unlikely(!debug_locks || current->lockdep_recursion))
>  		return;
>  
> +	current->lockdep_recursion++;
> +	barrier();

lockdep_off()?

>  	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
> -		return;
> +		goto end;
>  
>  	if (curr->hardirqs_enabled) {
>  		/*
> @@ -1910,6 +1921,9 @@ void trace_hardirqs_off(void)
>  		debug_atomic_inc(&hardirqs_off_events);
>  	} else
>  		debug_atomic_inc(&redundant_hardirqs_off);
> +end:
> +	barrier();
> +	current->lockdep_recursion--;

lockdep_on()?
-
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