On Mon. 10 Mar 2025 at 18:46, Oliver Hartkopp <socketcan@xxxxxxxxxxxx> wrote: > On 10.03.25 10:29, Vincent Mailhol wrote: > > On Mon. 10 Mar 2025 at 03:59, Oliver Hartkopp <socketcan@xxxxxxxxxxxx> wrote: (...) > >> Isn't there some lock-less per-cpu safe statistic handling within netdev > >> we might pick for our use-case? > > > > I see two solutions. Either we use lock_sock(skb->sk) and > > release_sock(skb->sk) or we can change the types of > > can_pkg_stats->tx_frames and can_pkg_stats->tx_frames_delta from long > > to atomic_long_t. > > > > The atomic_long_t is the closest solution to a lock-less. But my > > preference goes to the lock_sock() which looks more natural in this > > context. And look_sock() is just a spinlock which under the hood is > > also an atomic, so no big penalty either. > > When we get skbs from the netdevice (and not from user space), we do not > have a valid sk value. It is set to zero. > > See: > https://elixir.bootlin.com/linux/v6.13.6/source/net/can/raw.c#L203 > > And those skbs can also be forwarded by can-gw using can_send(). > > Therefore there is no lock_sock() without a valid sk ;-) > > When 'atomic_long_t' would also fix this simple statistics handling, we > should use that. I see, Thanks for the explanation. Then atomic_long_t seems the best (and easiest).
