Messages in this thread | | | Subject | Re: RCU stall when using function_graph | From | Pratyush Anand <> | Date | Wed, 9 Aug 2017 14:43:49 +0530 |
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On Sunday 06 August 2017 10:32 PM, Paul E. McKenney wrote: > On Sat, Aug 05, 2017 at 02:24:21PM +0900, 김동현 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! > > Hmmm... > > 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)?
-- Regards Pratyush
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