From e03c05ac9813410d15c9c39ccf02c84efe563533 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Thu, 18 Apr 2024 12:09:09 -0700 Subject: [PATCH] rethook: honor CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING in rethook_try_get() 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@mail.gmail.com/ Link: https://lore.kernel.org/all/20240418190909.704286-2-andrii@kernel.org/ Signed-off-by: Andrii Nakryiko Acked-by: Paul E. McKenney Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/rethook.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 4297a132a7ae..30d224946881 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); }