Hello, +CC netdev mailing-list
On 18.8.2020 23.12, Antonio Quartulli wrote: > Hi, > > On 18/08/2020 16:46, Jussi Kivilinna wrote: >> batadv_bla_send_claim() gets called from worker thread context through >> batadv_bla_periodic_work(), thus netif_rx_ni needs to be used in that >> case. This fixes "NOHZ: local_softirq_pending 08" log messages seen >> when batman-adv is enabled. >> >> Signed-off-by: Jussi Kivilinna <jussi.kivili...@haltian.com> >> --- >> net/batman-adv/bridge_loop_avoidance.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/net/batman-adv/bridge_loop_avoidance.c >> b/net/batman-adv/bridge_loop_avoidance.c >> index 5c41cc52bc53..ab6cec3c7586 100644 >> --- a/net/batman-adv/bridge_loop_avoidance.c >> +++ b/net/batman-adv/bridge_loop_avoidance.c >> @@ -437,7 +437,10 @@ static void batadv_bla_send_claim(struct batadv_priv >> *bat_priv, u8 *mac, >> batadv_add_counter(bat_priv, BATADV_CNT_RX_BYTES, >> skb->len + ETH_HLEN); >> >> - netif_rx(skb); >> + if (in_interrupt()) >> + netif_rx(skb); >> + else >> + netif_rx_ni(skb); > > What's the downside in calling netif_rx_ni() all the times? > Is there any possible side effect? > (consider this call is not along the fast path) Good question. I tried to find answer for this but found documentation being lacking on the issue, so I looked for examples and used 'in_interrupt/netif_rx/netif_rx_ni' bit that appears in few other places: https://elixir.bootlin.com/linux/v5.8/source/drivers/net/caif/caif_hsi.c#L469 https://elixir.bootlin.com/linux/v5.8/source/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c#L425 https://elixir.bootlin.com/linux/v5.8/source/drivers/net/wireless/marvell/libertas/rx.c#L153 https://elixir.bootlin.com/linux/v5.8/source/drivers/net/wireless/marvell/mwifiex/uap_txrx.c#L356 https://elixir.bootlin.com/linux/v5.8/source/net/caif/chnl_net.c#L121 Maybe someone on netdev mailing-list could give hint on this matter - should 'in_interrupt()?netif_rx(skb):netif_rx_ni(skb)' be used if context is not known or is just using 'netif_rx_ni(skb)' ok? > > On top of that, I just checked the definition of in_interrupt() and I > got this comment: > > * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() > really > * should not be used in new code. > > > Check > https://elixir.bootlin.com/linux/latest/source/include/linux/preempt.h#L85 > > Is that something we should consider or is the comment bogus? It very well be that the existing code that I looked at may not be the best for reuse today. -Jussi
