Re: [PATCH v3] net: use exponential backoff in netdev_wait_allrefs

From: Stephen Hemminger
Date: Thu Sep 17 2020 - 20:02:15 EST

On Thu, 17 Sep 2020 16:49:53 -0700
fruggeri@xxxxxxxxxx (Francesco Ruggeri) wrote:

> The combination of aca_free_rcu, introduced in commit 2384d02520ff
> ("net/ipv6: Add anycast addresses to a global hashtable"), and
> fib6_info_destroy_rcu, introduced in commit 9b0a8da8c4c6 ("net/ipv6:
> respect rcu grace period before freeing fib6_info"), can result in
> an extra rcu grace period being needed when deleting an interface,
> with the result that netdev_wait_allrefs ends up hitting the msleep(250),
> which is considerably longer than the required grace period.
> This can result in long delays when deleting a large number of interfaces,
> and it can be observed with this script:

Is there anyway to make RCU trigger faster?