Messages in this thread |  | | Date | Tue, 1 Aug 2017 20:12:14 -0400 | From | Steven Rostedt <> | Subject | Re: RCU stall when using function_graph |
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On Wed, 2 Aug 2017 00:15:44 +0200 Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
> On 02/08/2017 00:04, Paul E. McKenney wrote: > >> Hi Paul, > >> > >> I have been trying to set the function_graph tracer for ftrace and each time I > >> get a CPU stall. > >> > >> How to reproduce: > >> ----------------- > >> > >> echo function_graph > /sys/kernel/debug/tracing/current_tracer > >> > >> This error appears with v4.13-rc3 and v4.12-rc6.
Can you bisect this? It may be due to this commit:
0598e4f08 ("ftrace: Add use of synchronize_rcu_tasks() with dynamic trampolines")
-- Steve
> >> > >> Is it something already reported ? > > > > I have seen this sort of thing, but only when actually dumping the trace > > out, and I though those got fixed. You are seeing this just accumulating > > the trace? > > No, just by changing the tracer. It is the first operation I do after > rebooting and it is reproducible each time. That happens on an ARM64 > platform. > > > These RCU CPU stall warnings usually occur when something grabs hold of > > a CPU for too long, as in 21 seconds or so. One way that they can happen > > is excessive lock contention, another is having the kernel run through > > too much data at one shot. > > > > Adding Steven Rostedt on CC for his thoughts. > > >
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