On Mon, Jul 22, 2019 at 04:51:49AM -0700, Paul E. McKenney wrote: > > > > Would it make sense to have call_rcu() check to see if there are many > > > > outstanding requests on this CPU and if so process them before returning? > > > > That would ensure that frequent callers usually ended up doing their > > > > own processing. > > > > > > Unfortunately, no. Here is a code fragment illustrating why: That is only true in the general case though, kfree_rcu() doesn't have this problem since we know what the callback is doing. In general a caller of kfree_rcu() should not need to hold any locks while calling it. We could apply the same idea more generally and have some 'call_immediate_or_rcu()' which has restrictions on the caller's context. I think if we have some kind of problem here it would be better to handle it inside the core code and only require that callers use the correct RCU API. I can think of many places where kfree_rcu() is being used under user control.. Jason
