Re: [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference()

[Arnd Bergmann]

On Tuesday 23 February 2010, Paul E. McKenney wrote:
> This patch series adds lockdep-based checking to the rcu_dereference()
> primitive in order to flag misuses of RCU.

While I haven't looked much at this series, I've been thinking about
adding static diagnostics for rcu_dereference misuse, in the form of
an __rcu address space qualifier for pointers. Such a patch would
obviously conflict with this series, so I'd wait for yours to go
in first, but maybe you like the idea enough to do it yourself ;-).

The observation is that all accesses to an RCU protected pointer
are either through rcu_dereference, rcu_assign_pointer or one of their
variants. so it should be possible to add a new address space like we
have for __iomem, __user and soon __percpu and have sparse check that
we use RCU consistently on pointers that need it.

	Arnd
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