Hello Gur! On Tue, 2024-09-17 at 11:10 +0300, Gur Stavi wrote: > > @@ -1594,10 +1592,11 @@ void dsa_switch_shutdown(struct dsa_switch *ds) > > } > > > > /* Disconnect from further netdevice notifiers on the conduit, > > - * since netdev_uses_dsa() will now return false. > > + * from now on, netdev_uses_dsa_currently() will return false. > > */ > > dsa_switch_for_each_cpu_port(dp, ds) > > - dp->conduit->dsa_ptr = NULL; > > + rcu_assign_pointer(dp->conduit->dsa_ptr, NULL); > > + synchronize_rcu(); > > > > rtnl_unlock(); > > out: > > Hi, I am a newbie here. Thanks for the opportunity for learning more > about rcu. > Wouldn't it make more sense to call synchronize_rcu after rtnl_unlock? This is indeed a question which is usually resolved other way around (making locked section shorter), but in this particular case I thought that: - we actually don't need giving rtnl lock sooner, which would potentially make synchronize_rcu() call longer (if another thread manages to wake up and claim the rtnl lock before synchronize_rcu()) - we are in shutdown phase, we don't need to minimize lock contention, we need to minimize the overall shutdown time -- Alexander Sverdlin Siemens AG www.siemens.com
