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[2.104.116.184]) by smtp.gmail.com with ESMTPSA id u26-20020ac248ba000000b0047255d21188sm2597000lfg.183.2022.05.24.09.08.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 May 2022 09:08:09 -0700 (PDT) From: Hans Schultz X-Google-Original-From: Hans Schultz To: Nikolay Aleksandrov , Hans Schultz , davem@davemloft.net, kuba@kernel.org Cc: netdev@vger.kernel.org, Andrew Lunn , Vivien Didelot , Florian Fainelli , Vladimir Oltean , Eric Dumazet , Paolo Abeni , Jiri Pirko , Ivan Vecera , Roopa Prabhu , Shuah Khan , Daniel Borkmann , Ido Schimmel , linux-kernel@vger.kernel.org, bridge@lists.linux-foundation.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH V3 net-next 1/4] net: bridge: add fdb flag to extent locked port feature In-Reply-To: <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> References: <20220524152144.40527-1-schultz.hans+netdev@gmail.com> <20220524152144.40527-2-schultz.hans+netdev@gmail.com> <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> Date: Tue, 24 May 2022 18:08:08 +0200 Message-ID: <8635gyvrpz.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Hi Hans, > So this approach has a fundamental problem, f->dst is changed without any synchronization > you cannot rely on it and thus you cannot account for these entries properly. We must be very > careful if we try to add any new synchronization not to affect performance as well. > More below... > >> @@ -319,6 +326,9 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f, >> if (test_bit(BR_FDB_STATIC, &f->flags)) >> fdb_del_hw_addr(br, f->key.addr.addr); >> >> + if (test_bit(BR_FDB_ENTRY_LOCKED, &f->flags) && !test_bit(BR_FDB_OFFLOADED, &f->flags)) >> + atomic_dec(&f->dst->locked_entry_cnt); > > Sorry but you cannot do this for multiple reasons: > - f->dst can be NULL > - f->dst changes without any synchronization > - there is no synchronization between fdb's flags and its ->dst > > Cheers, > Nik Hi Nik, I could check if f->dst is NULL, but in general this should be able to work on a per port basis, so do you have an idea of how to keep a per port counter of added locked fdb entries? Best, Hans From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:in-reply-to:references:date:message-id :mime-version; bh=FYyqUIqX7o7uukxhOxpvy5c6jwFhAW9JG5e+iqj0ZAA=; b=c40RMye4tt3qCM6W7eagyel05d9f+ezi9QjwhaQUCVPrgeXySiIl9CgyIOCULFxZRD R6hBjevW71JnRlce8PS7Z25IqHWEruI0bmo1pEwvrEZrFMyulwV9euVsIFwx1faYR3pt IZOpC8zioCI8T2SnZoD3ZoSTFvlbhGEjtZ8ulllzeUUNb91lhIKU8erEgOQ+3jnIWFjx fiv+sihOx6bLRkA5OmLH/IMQpg6fnANudZqfBYeJtNmLbZiq+VIKRXePkKm+JBYSWSOK 2et3ghTg4DPaTlWwem54LXEFrT27VZvUKSFjYc7yQesvH60Ljkbai0rT9V3qfElTv5FM XxeQ== From: Hans Schultz In-Reply-To: <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> References: <20220524152144.40527-1-schultz.hans+netdev@gmail.com> <20220524152144.40527-2-schultz.hans+netdev@gmail.com> <01e6e35c-f5c9-9776-1263-058f84014ed9@blackwall.org> Date: Tue, 24 May 2022 18:08:08 +0200 Message-ID: <8635gyvrpz.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Bridge] [PATCH V3 net-next 1/4] net: bridge: add fdb flag to extent locked port feature List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikolay Aleksandrov , Hans Schultz , davem@davemloft.net, kuba@kernel.org Cc: Ivan Vecera , Andrew Lunn , Florian Fainelli , Jiri Pirko , Daniel Borkmann , netdev@vger.kernel.org, Ido Schimmel , bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Eric Dumazet , linux-kselftest@vger.kernel.org, Roopa Prabhu , Paolo Abeni , Vladimir Oltean , Shuah Khan , Vivien Didelot > > Hi Hans, > So this approach has a fundamental problem, f->dst is changed without any synchronization > you cannot rely on it and thus you cannot account for these entries properly. We must be very > careful if we try to add any new synchronization not to affect performance as well. > More below... > >> @@ -319,6 +326,9 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f, >> if (test_bit(BR_FDB_STATIC, &f->flags)) >> fdb_del_hw_addr(br, f->key.addr.addr); >> >> + if (test_bit(BR_FDB_ENTRY_LOCKED, &f->flags) && !test_bit(BR_FDB_OFFLOADED, &f->flags)) >> + atomic_dec(&f->dst->locked_entry_cnt); > > Sorry but you cannot do this for multiple reasons: > - f->dst can be NULL > - f->dst changes without any synchronization > - there is no synchronization between fdb's flags and its ->dst > > Cheers, > Nik Hi Nik, I could check if f->dst is NULL, but in general this should be able to work on a per port basis, so do you have an idea of how to keep a per port counter of added locked fdb entries? Best, Hans