From: "Paul E. McKenney" <[email protected]> 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 <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Daniel Borkmann <[email protected]> Cc: John Fastabend <[email protected]> Cc: Andrii Nakryiko <[email protected]> Cc: Martin KaFai Lau <[email protected]> Cc: Song Liu <[email protected]> Cc: Yonghong Song <[email protected]> Cc: KP Singh <[email protected]> Cc: Stanislav Fomichev <[email protected]> Cc: Hao Luo <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Ankur Arora <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: <[email protected]> Signed-off-by: Uladzislau Rezki (Sony) <[email protected]> --- 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 db7599c59c78..88673a4267eb 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); -- 2.39.2
