Re: [PATCH v2 33/44] ftrace: WARN on rcuidle
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2022-09-26 18:43:00
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Nit, the subject should have "tracing:" an not "ftrace:" as the former encompasses the tracing infrastructure and the latter is for the function hook part of that. On Mon, 19 Sep 2022 12:00:12 +0200 Peter Zijlstra [off-list ref] wrote:
quoted hunk ↗ jump to hunk
CONFIG_GENERIC_ENTRY disallows any and all tracing when RCU isn't enabled. XXX if s390 (the only other GENERIC_ENTRY user as of this writing) isn't comfortable with this, we could switch to HAVE_NOINSTR_VALIDATION which is x86_64 only atm. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- include/linux/tracepoint.h | 13 ++++++++++++- kernel/trace/trace.c | 3 +++ 2 files changed, 15 insertions(+), 1 deletion(-)--- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h@@ -178,6 +178,16 @@ static inline struct tracepoint *tracepo #endif /* CONFIG_HAVE_STATIC_CALL */ /* + * CONFIG_GENERIC_ENTRY archs are expected to have sanitized entry and idle + * code that disallow any/all tracing/instrumentation when RCU isn't watching. + */ +#ifdef CONFIG_GENERIC_ENTRY +#define RCUIDLE_COND(rcuidle) (rcuidle) +#else
Should probably move the below comment to here: /* srcu can't be used from NMI */
quoted hunk ↗ jump to hunk
+#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. */@@ -189,7 +199,8 @@ static inline struct tracepoint *tracepo return; \ \ /* srcu can't be used from NMI */ \
And remove the above. -- Steve
quoted hunk ↗ jump to hunk
- 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@@ -3104,6 +3104,9 @@ 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