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Subject[PATCH 9/9] tracing: Remove parent recording in latency tracer graph options
From: Steven Rostedt <srostedt@redhat.com>

Even though the parent is recorded with the normal function tracing
of the latency tracers (irqsoff and wakeup), the function graph
recording is bogus.

This is due to the function graph messing with the return stack.
The latency tracers pass in as the parent CALLER_ADDR0, which
works fine for plain function tracing. But this causes bogus output
with the graph tracer:

3) <idle>-0 | d.s3. 0.000 us | return_to_handler();
3) <idle>-0 | d.s3. 0.000 us | _raw_spin_unlock_irqrestore();
3) <idle>-0 | d.s3. 0.000 us | return_to_handler();
3) <idle>-0 | d.s3. 0.000 us | trace_hardirqs_on();
The "return_to_handle()" call is the trampoline of the
function graph tracer, and is meaningless in this context.

Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_functions_graph.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index af03ba9..b545634 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -287,7 +287,6 @@ trace_graph_function(struct trace_array *tr,
unsigned long ip, unsigned long parent_ip,
unsigned long flags, int pc)
{
- __trace_graph_function(tr, parent_ip, flags, pc);
__trace_graph_function(tr, ip, flags, pc);
}

--
1.7.1



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