Messages in this thread | | | Date | Tue, 23 Feb 2010 10:01:27 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() |
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On Tue, Feb 23, 2010 at 06:15:59PM +0100, Arnd Bergmann wrote: > 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.
Very good!
> > > 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.
Only the "next" pointer, not the "prev" pointer, but yes.
Perhaps it would be best to see if the sparse guys are willing to take this on?
Thanx, Paul
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