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Thu, 03 Apr 2025 09:24:18 -0700 (PDT) Received: from localhost ([2601:646:9e00:f56e:123b:cea3:439a:b3e3]) by smtp.gmail.com with UTF8SMTPSA id d2e1a72fcca58-739d97ee2b3sm1693762b3a.46.2025.04.03.09.24.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Apr 2025 09:24:18 -0700 (PDT) Date: Thu, 3 Apr 2025 09:24:17 -0700 From: Stanislav Fomichev To: Justin Iurman Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, kuniyu@amazon.com, Alexei Starovoitov , bpf Subject: Re: [PATCH net] net: lwtunnel: disable preemption when required Message-ID: References: <20250403083956.13946-1-justin.iurman@uliege.be> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250403083956.13946-1-justin.iurman@uliege.be> On 04/03, Justin Iurman wrote: > In lwtunnel_{input|output|xmit}(), dev_xmit_recursion() may be called in > preemptible scope for PREEMPT kernels. This patch disables preemption > before calling dev_xmit_recursion(). Preemption is re-enabled only at > the end, since we must ensure the same CPU is used for both > dev_xmit_recursion_inc() and dev_xmit_recursion_dec() (and any other > recursion levels in some cases) in order to maintain valid per-cpu > counters. Dummy question: CONFIG_PREEMPT_RT uses current->net_xmit.recursion to track the recursion. Any reason not to do it in the generic PREEMPT case?