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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Bryan Tan , Vishnu Dasa , Broadcom internal kernel review list , virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, berrange@redhat.com, Bobby Eshleman Subject: Re: [PATCH net-next v8 01/14] vsock: a per-net vsock NS mode state Message-ID: References: <20251023-vsock-vmtest-v8-0-dea984d02bb0@meta.com> <20251023-vsock-vmtest-v8-1-dea984d02bb0@meta.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Nov 06, 2025 at 05:16:29PM +0100, Stefano Garzarella wrote: > On Thu, Oct 23, 2025 at 11:27:40AM -0700, Bobby Eshleman wrote: > > From: Bobby Eshleman [...] > > @@ -65,6 +66,7 @@ struct vsock_sock { > > u32 peer_shutdown; > > bool sent_request; > > bool ignore_connecting_rst; > > + enum vsock_net_mode net_mode; > > > > /* Protected by lock_sock(sk) */ > > u64 buffer_size; > > @@ -256,4 +258,58 @@ static inline bool vsock_msgzerocopy_allow(const struct vsock_transport *t) > > { > > return t->msgzerocopy_allow && t->msgzerocopy_allow(); > > } > > + > > +static inline enum vsock_net_mode vsock_net_mode(struct net *net) > > +{ > > + enum vsock_net_mode ret; > > + > > + spin_lock_bh(&net->vsock.lock); > > + ret = net->vsock.mode; > > Do we really need a spin_lock just to set/get a variable? > What about WRITE_ONCE/READ_ONCE and/or atomic ? > > Not a strong opinion, just to check if we can do something like this: > > static inline enum vsock_net_mode vsock_net_mode(struct net *net) > { > return READ_ONCE(net->vsock.mode); > } > > static inline bool vsock_net_write_mode(struct net *net, u8 mode) > { > // Or using test_and_set_bit() if you prefer > if (xchg(&net->vsock.mode_locked, true)) > return false; > > WRITE_ONCE(net->vsock.mode, mode); > return true; > } > I think that works and seems worth it to avoid the lock on the read side. I'll move this over for the next rev. [...] Best, Bobby