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[73.170.40.124]) by smtp.gmail.com with UTF8SMTPSA id d2e1a72fcca58-74058dbba97sm9436665b3a.56.2025.05.06.10.12.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 May 2025 10:12:24 -0700 (PDT) Date: Tue, 6 May 2025 10:12:23 -0700 From: Stanislav Fomichev To: Cosmin Ratiu Cc: netdev@vger.kernel.org, Stanislav Fomichev , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "jiri @ resnulli . us" , Saeed Mahameed , Dragos Tatulea , linux-kselftest@vger.kernel.org Subject: Re: [PATCH net] net: Lock lower level devices when updating features Message-ID: References: <20250506142117.1883598-1-cratiu@nvidia.com> Precedence: bulk X-Mailing-List: linux-kselftest@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: <20250506142117.1883598-1-cratiu@nvidia.com> On 05/06, Cosmin Ratiu wrote: > __netdev_update_features() expects the netdevice to be ops-locked, but > it gets called recursively on the lower level netdevices to sync their > features, and nothing locks those. > > This commit fixes that, with the assumption that it shouldn't be possible > for both higher-level and lover-level netdevices to require the instance > lock, because that would lead to lock dependency warnings. > > Without this, playing with higher level (e.g. vxlan) netdevices on top > of netdevices with instance locking enabled can run into issues: Mentioning vxlan is a bit confusing here; it shouldn't let you flip lro (I think). Which upper are you testing against? Trying to understand if we can cover this case in the selftests. netdevsim also doesn't expose F_LRO feature... (yet?)