On Wed, Mar 31, 2010 at 06:37:34PM +0100, David Howells wrote: > Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > > Protected by something that the caller did, be it holding the the correct > > lock, operating on it during initialization before other CPUs have access > > to it, operating on it during cleanup after other CPUs' access has been > > revoked, or whatever. > > But the point I made very early this morning still stands: What if someone > simply wants to test the pointer, not actually to dereference it? OK, I was missing your point. And this is what you were proposing rcu_pointer_not_null() for. > NFS was using rcu_dereference() for this in a couple of places - which is > overkill. I suggested stripping this off and you countered with the > suggestion that it should be using rcu_dereference_check(). > > Why do I need anything at all? Right now you don't. We will need something as part of Arnd's patches to shut sparse up, and I was hoping not to have to go through the find/fix cycle twice. But that turned out to be kind of pointless, since we have burned far more time discussing than it would have taken to fix it twice. ;-) But the discussion has been helpful, as I was previously just fine with sprinkling otherwise-unneed rcu_dereference_whatever() calls thoughout the kernel! Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
