From: Matt Mackall This avoids a nasty NAPI race by checking that work was actually scheduled for the CPU netpoll is running on and pulls the NAPI-specific code out into a separate function. Original idea from Jeff Moyer Tested by Andrew Tridgell Signed-off-by: Matt Mackall Signed-off-by: Andrew Morton --- 25-akpm/net/core/netpoll.c | 41 +++++++++++++++++++++++++---------------- 1 files changed, 25 insertions(+), 16 deletions(-) diff -puN net/core/netpoll.c~netpoll-fix-napi-polling-race-on-smp net/core/netpoll.c --- 25/net/core/netpoll.c~netpoll-fix-napi-polling-race-on-smp Tue Jan 11 14:41:14 2005 +++ 25-akpm/net/core/netpoll.c Tue Jan 11 14:41:14 2005 @@ -65,27 +65,25 @@ static int checksum_udp(struct sk_buff * return csum_fold(skb_checksum(skb, 0, skb->len, skb->csum)); } -void netpoll_poll(struct netpoll *np) +/* + * Check whether delayed processing was scheduled for our current CPU, + * and then manually invoke NAPI polling to pump data off the card. + * + * In cases where there is bi-directional communications, reading only + * one message at a time can lead to packets being dropped by the + * network adapter, forcing superfluous retries and possibly timeouts. + * Thus, we set our budget to greater than 1. + */ +static void poll_napi(struct netpoll *np) { - /* - * In cases where there is bi-directional communications, reading - * only one message at a time can lead to packets being dropped by - * the network adapter, forcing superfluous retries and possibly - * timeouts. Thus, we set our budget to a more reasonable value. - */ int budget = 16; unsigned long flags; + struct softnet_data *queue; - if(!np->dev || !netif_running(np->dev) || !np->dev->poll_controller) - return; - - /* Process pending work on NIC */ - np->dev->poll_controller(np->dev); - - /* If scheduling is stopped, tickle NAPI bits */ spin_lock_irqsave(&netpoll_poll_lock, flags); - if (np->dev->poll && - test_bit(__LINK_STATE_RX_SCHED, &np->dev->state)) { + queue = &__get_cpu_var(softnet_data); + if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) && + !list_empty(&queue->poll_list)) { np->dev->netpoll_rx |= NETPOLL_RX_DROP; atomic_inc(&trapped); @@ -95,6 +93,17 @@ void netpoll_poll(struct netpoll *np) np->dev->netpoll_rx &= ~NETPOLL_RX_DROP; } spin_unlock_irqrestore(&netpoll_poll_lock, flags); +} + +void netpoll_poll(struct netpoll *np) +{ + if(!np->dev || !netif_running(np->dev) || !np->dev->poll_controller) + return; + + /* Process pending work on NIC */ + np->dev->poll_controller(np->dev); + if (np->dev->poll) + poll_napi(np); zap_completion_queue(); } _