Re: [tip:sched/core] [tracing, hardirq] 9aedeaed6f: WARNING:suspicious_RCU_usage
flat view
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2023-01-21 16:49:13
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On Fri, 20 Jan 2023 10:51:18 +0100 Peter Zijlstra [off-list ref] wrote:
quoted
does trigger the issue, you can then bisect the functions with the script: scripts/tracing/ftrace-bisect.shPff, 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
quoted hunk ↗ jump to hunk
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;