diff options
author | Michael S. Tsirkin <mst@redhat.com> | 2012-05-16 03:57:12 -0400 |
---|---|---|
committer | Michael S. Tsirkin <mst@redhat.com> | 2012-05-17 05:16:38 -0400 |
commit | ec13ee80145ccb95b00e6e610044bbd94a170051 (patch) | |
tree | 44c1f5ef734398ec15e0ca2dd45a1a474899919c | |
parent | b8ae0eb320b38415da94a41f75e9f99e0aaff06c (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 <uobergfe@redhat.com>
Tested-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r-- | drivers/net/virtio_net.c | 2 |
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) | |||
492 | * We synchronize against interrupts via NAPI_STATE_SCHED */ | 492 | * We synchronize against interrupts via NAPI_STATE_SCHED */ |
493 | if (napi_schedule_prep(&vi->napi)) { | 493 | if (napi_schedule_prep(&vi->napi)) { |
494 | virtqueue_disable_cb(vi->rvq); | 494 | virtqueue_disable_cb(vi->rvq); |
495 | local_bh_disable(); | ||
495 | __napi_schedule(&vi->napi); | 496 | __napi_schedule(&vi->napi); |
497 | local_bh_enable(); | ||
496 | } | 498 | } |
497 | } | 499 | } |
498 | 500 | ||