| Message ID | 20170616172400.10809-1-bigeasy@linutronix.de |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Fri, 16 Jun 2017 19:23:59 +0200 > In 2004 [0] netif_rx_ni() gained a preempt_disable() section around > netif_rx() and its do_softirq() + testing for it. The do_softirq() part > is required because netif_rx() raises the softirq but does not invoke > it. The preempt_disable() is required to avoid running the BH in > parallel. > All this can be avoided be putting this into a local_bh_disable()ed > section. The local_bh_enable() part will invoke do_softirq() if > required. > > [0] Make netif_rx_ni preempt-safe > http://oss.sgi.com/projects/netdev/archive/2004-10/msg02211.html > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Why make extra work? The current code is cheaper. Doing all of that dance with the local_bh_enable() function call is more expensive than the inlined counter bump and softirq state check. I'm not applying this without a better justification, sorry.
diff --git a/net/core/dev.c b/net/core/dev.c index b8d6dd9e8b5c..b1f8a89322bd 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3928,11 +3928,9 @@ int netif_rx_ni(struct sk_buff *skb) trace_netif_rx_ni_entry(skb); - preempt_disable(); + local_bh_disable(); err = netif_rx_internal(skb); - if (local_softirq_pending()) - do_softirq(); - preempt_enable(); + local_bh_enable(); return err; }
In 2004 [0] netif_rx_ni() gained a preempt_disable() section around netif_rx() and its do_softirq() + testing for it. The do_softirq() part is required because netif_rx() raises the softirq but does not invoke it. The preempt_disable() is required to avoid running the BH in parallel. All this can be avoided be putting this into a local_bh_disable()ed section. The local_bh_enable() part will invoke do_softirq() if required. [0] Make netif_rx_ni preempt-safe http://oss.sgi.com/projects/netdev/archive/2004-10/msg02211.html Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- net/core/dev.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)