On Sat, May 09, 2020 at 11:25:16AM +0200, Peter Zijlstra wrote: > Right; it's just that the moment you do trigger it, it'll iterate that > pgd_list and that is potentially huge. Then again, that's not a new > problem. > > I suppose we can deal with it if/when it becomes an actual problem. > > I had a quick look and I think it might be possible to make it an RCU > managed list. We'd have to remove the pgd_list entry in > put_task_struct_rcu_user(). Then we can play games in sync_global_*() > and use RCU iteration. New tasks (which can be missed in the RCU > iteration) will already have a full clone of the PGD anyway. Right, it should not be that difficult to rcu-protect the pgd-list, but we can try that when it actually becomes a problem. Joerg
