On Sunday 06 August 2017 10:32 PM, Paul E. McKenney wrote:
On Sat, Aug 05, 2017 at 02:24:21PM +0900, κΉ€λ™ν˜„ wrote:
Dear All

As for me, after configuring function_graph as below, crash disappears.
"echo 0 > d/tracing/tracing_on"
"sleep 1"

"echo function_graph > d/tracing/current_tracer"
"sleep 1"

"echo smp_call_function_single > d/tracing/set_ftrace_filter"

It will limit trace output to only for the filtered function (smp_call_function_single).

adb shell "sleep 1"

"echo 1 > d/tracing/tracing_on"
adb shell "sleep 1"

Right after function_graph is enabled, too many logs are traced upon IRQ
transaction which many times eventually causes stall.

That would do it!


Steven, would it be helpful if RCU were to inform tracing (say) halfway
through the RCU CPU stall interval, allowing the tracer to do something
like cond_resched_rcu_qs()?  I can imagine all sorts of reasons why this
wouldn't work, for example, if all the tracing was with irqs disabled
or some such, but figured I should ask.

Does Guillermo's approach work for others?

Limited output with a couple of filtered function will definitely not cause RCU schedule stall. But the question is whether we should expect a full function graph trace working on every platform or not (specially the one which generates high interrupts)?


Reply via email to