On Fri, 29 Jan 2021 10:18:12 -0800 Wei Wang wrote:
> This patch adds a new sysfs attribute to the network device class.
> Said attribute provides a per-device control to enable/disable the
> threaded mode for all the napi instances of the given network device,
> without the need for a device up/down.
> User sets it to 1 or 0 to enable or disable threaded mode.
>
> Co-developed-by: Paolo Abeni <pab...@redhat.com>
> Signed-off-by: Paolo Abeni <pab...@redhat.com>
> Co-developed-by: Hannes Frederic Sowa <han...@stressinduktion.org>
> Signed-off-by: Hannes Frederic Sowa <han...@stressinduktion.org>
> Co-developed-by: Felix Fietkau <n...@nbd.name>
> Signed-off-by: Felix Fietkau <n...@nbd.name>
> Signed-off-by: Wei Wang <wei...@google.com>
> +static int napi_set_threaded(struct napi_struct *n, bool threaded)
> +{
> + int err = 0;
> +
> + if (threaded == !!test_bit(NAPI_STATE_THREADED, &n->state))
> + return 0;
> +
> + if (!threaded) {
> + clear_bit(NAPI_STATE_THREADED, &n->state);
Can we put a note in the commit message saying that stopping the
threads is slightly tricky but we'll do it if someone complains?
Or is there a stronger reason than having to wait for thread to finish
up with the NAPI not to stop them?
> + return 0;
> + }
> +
> + if (!n->thread) {
> + err = napi_kthread_create(n);
> + if (err)
> + return err;
> + }
> +
> + /* Make sure kthread is created before THREADED bit
> + * is set.
> + */
> + smp_mb__before_atomic();
> + set_bit(NAPI_STATE_THREADED, &n->state);
> +
> + return 0;
> +}
> +
> +static void dev_disable_threaded_all(struct net_device *dev)
> +{
> + struct napi_struct *napi;
> +
> + list_for_each_entry(napi, &dev->napi_list, dev_list)
> + napi_set_threaded(napi, false);
> + dev->threaded = 0;
> +}
> +
> +int dev_set_threaded(struct net_device *dev, bool threaded)
> +{
> + struct napi_struct *napi;
> + int ret;
> +
> + dev->threaded = threaded;
> + list_for_each_entry(napi, &dev->napi_list, dev_list) {
> + ret = napi_set_threaded(napi, threaded);
> + if (ret) {
> + /* Error occurred on one of the napi,
> + * reset threaded mode on all napi.
> + */
> + dev_disable_threaded_all(dev);
> + break;
> + }
> + }
> +
> + return ret;
> +}
> +
> void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
> int (*poll)(struct napi_struct *, int), int weight)
> {
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index daf502c13d6d..884f049ee395 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -538,6 +538,55 @@ static ssize_t phys_switch_id_show(struct device *dev,
> }
> static DEVICE_ATTR_RO(phys_switch_id);
>
> +static ssize_t threaded_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct net_device *netdev = to_net_dev(dev);
> + int ret;
> +
> + if (!rtnl_trylock())
> + return restart_syscall();
> +
> + if (!dev_isalive(netdev)) {
> + ret = -EINVAL;
> + goto unlock;
> + }
> +
> + if (list_empty(&netdev->napi_list)) {
> + ret = -EOPNOTSUPP;
> + goto unlock;
> + }
Maybe others disagree but I'd take this check out. What's wrong with
letting users see that threaded napi is disabled for devices without
NAPI?
This will also help a little devices which remove NAPIs when they are
down.
I've been caught off guard in the past by the fact that kernel returns
-ENOENT for XPS map when device has a single queue.
> + ret = sprintf(buf, fmt_dec, netdev->threaded);
> +
> +unlock:
> + rtnl_unlock();
> + return ret;
> +}
> +
> +static int modify_napi_threaded(struct net_device *dev, unsigned long val)
> +{
> + int ret;
> +
> + if (list_empty(&dev->napi_list))
> + return -EOPNOTSUPP;
> +
> + if (val != 0 && val != 1)
> + return -EOPNOTSUPP;
> +
> + ret = dev_set_threaded(dev, val);
> +
> + return ret;
return dev_set_threaded(dev, val);
> +}
