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[RFC,bpf] Chose RCU Tasks based on TASKS_RCU rather than PREEMPTION

Message ID 847ac98b-886d-4f91-b961-2bb452555af0@paulmck-laptop (mailing list archive)
State RFC
Delegated to: BPF
Headers show
Series [RFC,bpf] Chose RCU Tasks based on TASKS_RCU rather than PREEMPTION | expand

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Commit Message

Paul E. McKenney Feb. 28, 2024, 7:41 p.m. UTC 
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.

Only build tested.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Ankur Arora <ankur.a.arora@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <bpf@vger.kernel.org>
diff mbox series

Patch

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index d382f5ebe06c8..5085f66b33890 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);