linux-kernel - Re: [PATCHv2 1/3] tracing: proper check for irq

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Date:	Thu, 23 Sep 2010 15:48:13 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	fweisbec@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 1/3] tracing: proper check for irq_depth routines

On Thu, 2010-09-23 at 14:00 +0200, Jiri Olsa wrote:
> The check_irq_entry and check_irq_return could be called
> from graph event context. In such case there's no graph
> private data allocated. Adding checks to handle this case.
> 
> wbr,
> jirka
> 
> 
> Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> ---
>  kernel/trace/trace_functions_graph.c |   24 ++++++++++++++++++++----
>  1 files changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index 02c708a..1390159 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -887,12 +887,20 @@ check_irq_entry(struct trace_iterator *iter, u32 flags,
>  		unsigned long addr, int depth)
>  {
>  	int cpu = iter->cpu;
> +	int *depth_irq;
>  	struct fgraph_data *data = iter->private;
> -	int *depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
>  
> -	if (flags & TRACE_GRAPH_PRINT_IRQS)
> +	/*
> +	 * We either display irqs, or we got called as
> +	 * graph event, and out private data do no exist.

"out private data do no exist" makes no sense.

> +	 * In both cases we bypass the irq check.
> +	 */
> +	if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
> +	    (!data))
>  		return 0;
>  
> +	depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
> +
>  	/*
>  	 * We are inside the irq code
>  	 */
> @@ -925,12 +933,20 @@ static int
>  check_irq_return(struct trace_iterator *iter, u32 flags, int depth)
>  {
>  	int cpu = iter->cpu;
> +	int *depth_irq;
>  	struct fgraph_data *data = iter->private;
> -	int *depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
>  
> -	if (flags & TRACE_GRAPH_PRINT_IRQS)
> +	/*
> +	 * We either display irqs, or we got called as
> +	 * graph event, and out private data do no exist.

ditto.

-- Steve

> +	 * In both cases we bypass the irq check.
> +	 */
> +	if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
> +	    (!data))
>  		return 0;
>  
> +	depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
> +
>  	/*
>  	 * We are not inside the irq code.
>  	 */


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