Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() | Date | Tue, 23 Feb 2010 18:15:59 +0100 |
| |
On Tuesday 23 February 2010, Paul E. McKenney wrote: > We would also need something for initialization of structure fields. > Does __force work in that case as well?
Yes, it will just need some syntactical sugar to avoid placing __force in device drivers.
> > If there are cases where it does not work, we need to come up with > > names for new primitives that just do the assignment or dereference > > with __force but no actual synchronization. > > Some data structures are shared by RCU and non-RCU code, with struct > list_head being the most prominent example. Making the "next" pointer > as __rcu might be OK, but there are a -lot- of non-RCU uses of struct > list_head. Would we really want to introduce rcu_dereference() to all > non-RCU list-traversal primitives, or do we need to do something else?
I've just started an experimental implementation and got stuck at list rcu. The two to deal with it that I can see are - ignore list-rcu for now, and make all include/linux/rculist.h __force the problem to be ignored. - introduce a new struct rcu_list_head that needs to be used for list rcu.
A nicer option might be if sparse would let you write 'struct list_head __rcu head' and interpret that as having the pointers inside it annotated as __rcu.
Arnd
| |