Messages in this thread |  | | Date | Sat, 21 Jan 2023 11:49:04 -0500 | From | Steven Rostedt <> | Subject | Re: [tip:sched/core] [tracing, hardirq] 9aedeaed6f: WARNING:suspicious_RCU_usage |
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On Fri, 20 Jan 2023 10:51:18 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> > does trigger the issue, you can then bisect the functions with the script: > > > > scripts/tracing/ftrace-bisect.sh > > Pff, that all sounds like actual work :-) > > Instead I did me the below hack and added my early_printk() hacks and > that got me a usable backtrace.
Well, if you system is still running after the issue, then sure. I created this when it would cause a triple fault reboot. In which case, there was no real debugging output to use.
-- Steve
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c > index 5e7ead52cfdb..7defc6e24f8f 100644 > --- a/arch/x86/kernel/ftrace.c > +++ b/arch/x86/kernel/ftrace.c > @@ -646,6 +646,9 @@ void prepare_ftrace_return(unsigned long ip, unsigned long *parent, > if (unlikely(atomic_read(¤t->tracing_graph_pause))) > return; > > + if (WARN_ONCE(!rcu_is_watching(), "RCU not on for: %pS\n", (void *)ip)) > + return; > + > bit = ftrace_test_recursion_trylock(ip, *parent); > if (bit < 0) > return;
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