[PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
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STALE1366d
From: Peter Zijlstra <peterz@infradead.org>
Date: 2023-01-23 20:58:44
Also in:
kvm, linux-pm, lkml, virtualization
Subsystem:
function hooks (ftrace), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Steven Rostedt, Masami Hiramatsu, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
All RCU disabled code should be noinstr and hence we should never get here -- when we do, WARN about it and make sure to not actually do tracing. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/kernel/ftrace.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c@@ -646,6 +646,9 @@ void prepare_ftrace_return(unsigned long 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;