On Thu, Apr 18, 2024 at 12:09:09PM -0700, Andrii Nakryiko wrote: > Take into account CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING when validating > that RCU is watching when trying to setup rethooko on a function entry. > > One notable exception when we force rcu_is_watching() check is > CONFIG_KPROBE_EVENTS_ON_NOTRACE=y case, in which case kretprobes will use > old-style int3-based workflow instead of relying on ftrace, making RCU > watching check important to validate. > > This further (in addition to improvements in the previous patch) > improves BPF multi-kretprobe (which rely on rethook) runtime throughput > by 2.3%, according to BPF benchmarks ([0]). > > [0] https://lore.kernel.org/bpf/CAEf4BzauQ2WKMjZdc9s0rBWa01BYbgwHN6aNDXQSHYia47pQ-w@xxxxxxxxxxxxxx/ > > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > --- > kernel/trace/rethook.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c > index fa03094e9e69..a974605ad7a5 100644 > --- a/kernel/trace/rethook.c > +++ b/kernel/trace/rethook.c > @@ -166,6 +166,7 @@ struct rethook_node *rethook_try_get(struct rethook *rh) > if (unlikely(!handler)) > return NULL; > > +#if defined(CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING) || defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE) > /* > * This expects the caller will set up a rethook on a function entry. > * When the function returns, the rethook will eventually be reclaimed > @@ -174,6 +175,7 @@ struct rethook_node *rethook_try_get(struct rethook *rh) > */ > if (unlikely(!rcu_is_watching())) > return NULL; > +#endif > > return (struct rethook_node *)objpool_pop(&rh->pool); > } > -- > 2.43.0 >
