On Wed, Feb 28, 2024 at 01:31:12PM -0500, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <[email protected]> > > There are two WARN_ON*() warnings in tracepoint.h that deal with RCU > usage. But when they trigger, especially from using a TRACE_EVENT() > macro, the information is not very helpful and is confusing: > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 0 at include/trace/events/lock.h:24 > lock_acquire+0x2b2/0x2d0 > > Where the above warning takes you to: > > TRACE_EVENT(lock_acquire, <<<--- line 24 in lock.h > > TP_PROTO(struct lockdep_map *lock, unsigned int subclass, > int trylock, int read, int check, > struct lockdep_map *next_lock, unsigned long ip), > [..] > > Change the WARN_ON_ONCE() to WARN_ONCE() and add a string that allows > someone to search for exactly where the bug happened. > > Reported-by: Borislav Petkov <[email protected]> > Signed-off-by: Steven Rostedt (Google) <[email protected]>
Reviewed-by: Paul E. McKenney <[email protected]> > --- > include/linux/tracepoint.h | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 88c0ba623ee6..689b6d71590e 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -199,7 +199,8 @@ static inline struct tracepoint > *tracepoint_ptr_deref(tracepoint_ptr_t *p) > if (!(cond)) \ > return; \ > \ > - if (WARN_ON_ONCE(RCUIDLE_COND(rcuidle))) \ > + if (WARN_ONCE(RCUIDLE_COND(rcuidle), \ > + "Bad RCU usage for tracepoint")) \ > return; \ > \ > /* keep srcu and sched-rcu usage consistent */ \ > @@ -259,7 +260,8 @@ static inline struct tracepoint > *tracepoint_ptr_deref(tracepoint_ptr_t *p) > TP_ARGS(args), \ > TP_CONDITION(cond), 0); \ > if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \ > - WARN_ON_ONCE(!rcu_is_watching()); \ > + WARN_ONCE(!rcu_is_watching(), \ > + "RCU not watching for tracepoint"); \ > } \ > } \ > __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args), \ > -- > 2.43.0 >
