[PATCH v3 34/51] trace: WARN on rcuidle

Peter Zijlstra
2023-01-12T20:04:21Z

ARCH_WANTS_NO_INSTR (a superset of CONFIG_GENERIC_ENTRY) disallows any
and all tracing when RCU isn't enabled.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
---
include/linux/tracepoint.h | 15 +++++++++++++--
kernel/trace/trace.c | 3 +++
2 files changed, 16 insertions(+), 2 deletions(-)

--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -178,6 +178,17 @@ static inline struct tracepoint *tracepo
#endif /* CONFIG_HAVE_STATIC_CALL */

/*
+ * ARCH_WANTS_NO_INSTR archs are expected to have sanitized entry and idle
+ * code that disallow any/all tracing/instrumentation when RCU isn't watching.
+ */
+#ifdef CONFIG_ARCH_WANTS_NO_INSTR
+#define RCUIDLE_COND(rcuidle) (rcuidle)
+#else
+/* srcu can't be used from NMI */
+#define RCUIDLE_COND(rcuidle) (rcuidle && in_nmi())
+#endif
+
+/*
* it_func[0] is never NULL because there is at least one element in the array
* when the array itself is non NULL.
*/
@@ -188,8 +199,8 @@ static inline struct tracepoint *tracepo
if (!(cond)) \
return; \
\
- /* srcu can't be used from NMI */ \
- WARN_ON_ONCE(rcuidle && in_nmi()); \
+ if (WARN_ON_ONCE(RCUIDLE_COND(rcuidle))) \
+ return; \
\
/* keep srcu and sched-rcu usage consistent */ \
preempt_disable_notrace(); \
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3119,6 +3119,9 @@ void __trace_stack(struct trace_array *t
return;
}

+ if (WARN_ON_ONCE(IS_ENABLED(CONFIG_GENERIC_ENTRY)))
+ return;
+
/*
* When an NMI triggers, RCU is enabled via ct_nmi_enter(),
* but if the above rcu_is_watching() failed, then the NMI