On Thu, Nov 17, 2022 at 4:52 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > Hi Eric, > > On Thu, Nov 17, 2022 at 01:58:18PM -0800, Eric Dumazet wrote: > > On Wed, Nov 16, 2022 at 7:16 PM Joel Fernandes (Google) > > <joel@xxxxxxxxxxxxxxxxx> wrote: > > > > > > In a networking test on ChromeOS, we find that using the new CONFIG_RCU_LAZY > > > causes a networking test to fail in the teardown phase. > > > > > > The failure happens during: ip netns del <name> > > > > > > Using ftrace, I found the callbacks it was queuing which this series fixes. Use > > > call_rcu_flush() to revert to the old behavior. With that, the test passes. > > > > > > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> > > > --- > > > net/ipv4/devinet.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c > > > index e8b9a9202fec..98b20f333e00 100644 > > > --- a/net/ipv4/devinet.c > > > +++ b/net/ipv4/devinet.c > > > @@ -328,7 +328,7 @@ static void inetdev_destroy(struct in_device *in_dev) > > > neigh_parms_release(&arp_tbl, in_dev->arp_parms); > > > arp_ifdown(dev); > > > > > > - call_rcu(&in_dev->rcu_head, in_dev_rcu_put); > > > + call_rcu_flush(&in_dev->rcu_head, in_dev_rcu_put); > > > } > > > > For this one, I suspect the issue is about device refcount lingering ? > > > > I think we should release refcounts earlier (and only delegate the > > freeing part after RCU grace period, which can be 'lazy' just fine) > > > > Something like: > > The below diff where you reduce refcount before RCU grace period, also makes the > test pass. > > If you are Ok with it, I can roll it into a patch with your Author tag and my > Tested-by. Let me know what you prefer? > > Also, looking through the patch, I don't see any issue. One thing is > netdev_put() now happens before a grace period, instead of after. But I don't > think that's an issue. Normally the early netdev_put() is fine, because these netdev are already fully RCU protected. Sure, feel free to take this patch as is, thanks.
