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Fri, 30 Oct 2026 15:22:25 -0700 (PDT) Received: from localhost ([153.61.198.241]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8aada3d38eesm414805b3a.40.2026.10.30.15.22.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Oct 2026 15:22:24 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Fri, 30 Oct 2026 22:22:24 +0000 Message-Id: To: , "Daniel Borkmann" , "Andrii Nakryiko" Cc: "Martin KaFai Lau" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "John Fastabend" , "Shuah Khan" , , , Subject: Re: [PATCH RFC bpf-next 0/2] bpf: Do not let preemption cause false recursion drops in trampoline progs From: "Alexei Starovoitov" In-Reply-To: <20261025-b4-bpf-trampoline-preempt-v1-0-198dcdc0c6ac@sentinelone.com> References: <20261025-b4-bpf-trampoline-preempt-v1-0-198dcdc0c6ac@sentinelone.com> Content-Transfer-Encoding: 8bit X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Sun, Oct 25, 2026 at 04:02 AM Mike Bazov via B4 Relay wrote: > Is disabling preemption in __bpf_prog_enter_recur() on !PREEMPT_RT the > preferred fix for fentry/fexit, or would you prefer a different > mechanism for reconciling preemptible execution with prog->active and > the per-CPU private stack? No. We cannot disable preemption, since progs are not short with may_goto they can take 1/4 sec. Sounds like private stack is the culprit. Should we disable it? pw-bot: cr