On Mon, Sep 19, 2022 at 12:00:12PM +0200, Peter Zijlstra wrote: > 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@xxxxxxxxxxxxx> > --- > 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 > +#define RCUIDLE_COND(rcuidle) (rcuidle && in_nmi()) > +#endif Could we make this depend on ARCH_WANTS_NO_INSTR instead? That'll allow arm64 to check this even though we're not using the generic entry code (and there's lots of work necessary to make that possible...). Thanks, Mark. > + > +/* > * 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 */ \ > - 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 > >
