On Fri, Aug 17, 2018 at 09:08:42AM -0700, Tejun Heo wrote: > Hello, > > On Tue, Aug 14, 2018 at 10:06:18AM -0700, Paul E. McKenney wrote: > > > Is there a way we could make a union, or reuse one of the other fields, > > > as we know that synchronize_srcu() can't be used yet (and if it is, > > > either warn, or just make it a nop). And when we call srcu_init() and > > > remove the srcu_struct from the list, we can then initialize whatever > > > we used as the temporary boot up list field. > > > > I will take a look. If nothing else, I could union it with the > > struct work_struct, since it cannot be used that early anyway. ;-) > > > > Or I could just use the work_struct that is already inside the struct > > work_struct. Tejun, would you be OK with that? > > Hmm... not super against it given how specialized the whole thing is > but maybe just making it a union is cleaner?
The problem with making it be a union is that I cannnot determine how to initialize it due to the possibility that someone will initialize it early, but not use it until much later. For example, if I initialize my side of the union, but they don't actually use it until after rcu_init() is invoked, I will end up passing a bogus work_struct to you. In theory, I could straighten all this out at rcu_init() time, but that would require linking all srcu_struct instances initialized at that point, including the compile-time-initialized instances. This can of course be done, but not simply. Or am I missing a trick here somewhere? Thanx, Paul