On Tue 16 May 2023 at 17:39, Jakub Kicinski [off-list ref] wrote:

On Tue, 16 May 2023 15:58:46 -0700 Peilin Ye wrote:

quoted

quoted

Given Peilin's investigation I think fix without changing core may
indeed be hard. I'm not sure if returning -EBUSY when qdisc refcnt
is elevated will be appreciated by the users, do we already have
similar behavior in other parts of TC?  

Seems like trying to delete an "in-use" cls_u32 filter returns -EBUSY

I meant -EBUSY due to a race (another operation being in flight).
I think that's different.

I wonder if somehow leveraging existing tc_modify_qdisc() 'replay'
functionality instead of returning error to the user would be a better
approach? Currently the function is replayed when qdisc_create() returns
EAGAIN. It should be trivial to do the same for qdisc_graft() result.