diff options
authorMichael S. Tsirkin <>2012-05-16 10:57:12 +0300
committerMichael S. Tsirkin <>2012-05-17 12:16:38 +0300
commitec13ee80145ccb95b00e6e610044bbd94a170051 (patch)
parentb8ae0eb320b38415da94a41f75e9f99e0aaff06c (diff)
virtio_net: invoke softirqs after __napi_schedule
__napi_schedule might raise softirq but nothing causes do_softirq to trigger, so it does not in fact run. As a result, the error message "NOHZ: local_softirq_pending 08" sometimes occurs during boot of a KVM guest when the network service is started and we are oom: ... Bringing up loopback interface: [ OK ] Bringing up interface eth0: Determining IP information for eth0...NOHZ: local_softirq_pending 08 done. [ OK ] ... Further, receive queue processing might get delayed indefinitely until some interrupt triggers: virtio_net expected napi to be run immediately. One way to cause do_softirq to be executed is by invoking local_bh_enable(). As __napi_schedule is normally called from bh or irq context, this seems to make sense: disable bh before __napi_schedule and enable afterwards. In fact it's a very complicated way of calling do_softirq(), and works since this function is only used when we are not in interrupt context. It's not hot at all, in any ideal scenario. Reported-by: Ulrich Obergfell <> Tested-by: Ulrich Obergfell <> Signed-off-by: Michael S. Tsirkin <> Acked-by: Rusty Russell <>
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index af8acc85f4bb..cbefe671bcc6 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -492,7 +492,9 @@ static void virtnet_napi_enable(struct virtnet_info *vi)
* We synchronize against interrupts via NAPI_STATE_SCHED */
if (napi_schedule_prep(&vi->napi)) {
+ local_bh_disable();
+ local_bh_enable();