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

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Date:	Fri, 24 Sep 2010 17:41:02 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	fweisbec@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 1/3] tracing: proper check for irq_depth routines

On Thu, Sep 23, 2010 at 03:48:13PM -0400, Steven Rostedt wrote:
> 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.
> >  	 */
> 
> 

hi,
attaching changed patch

thanks,
jirka

---
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 private data do no exist.
+	 * 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 private data do no exist.
+	 * 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.
 	 */
-- 
1.7.1

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