From 1e52af7f023c44859868306fac1a4b6b556cf47b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 28 Feb 2024 11:17:28 -0800 Subject: [PATCH] bpf: Choose RCU Tasks based on TASKS_RCU rather than PREEMPTION The advent of CONFIG_PREEMPT_AUTO, AKA lazy preemption, will mean that even kernels built with CONFIG_PREEMPT_NONE or CONFIG_PREEMPT_VOLUNTARY might see the occasional preemption, and that this preemption just might happen within a trampoline. Therefore, update bpf_tramp_image_put() to choose call_rcu_tasks() based on CONFIG_TASKS_RCU instead of CONFIG_PREEMPTION. This change might enable further simplifications, but the goal of this effort is to make the code safe, not necessarily optimal. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: John Fastabend Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: KP Singh Cc: Stanislav Fomichev Cc: Hao Luo Cc: Jiri Olsa Cc: Ankur Arora Cc: Thomas Gleixner Cc: Signed-off-by: Uladzislau Rezki (Sony) --- kernel/bpf/trampoline.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index db7599c59c78a..88673a4267ebd 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -333,7 +333,7 @@ static void bpf_tramp_image_put(struct bpf_tramp_image *im) int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP, NULL, im->ip_epilogue); WARN_ON(err); - if (IS_ENABLED(CONFIG_PREEMPTION)) + if (IS_ENABLED(CONFIG_TASKS_RCU)) call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks); else percpu_ref_kill(&im->pcref); -- 2.30.2