From: Herbert Xu
> Sent: 16 May 2019 08:20
> As cmpxchg is a non-RCU mechanism it will cause sparse warnings
> when we use it for RCU. This patch adds explicit casts to silence
> those warnings. This should probably be moved to RCU itself in
> future.
>
...
> - if (cmpxchg(prev, NULL, ntbl) == NULL)
> + if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL)
I presume these casts remove an 'rcu' marker on the variable.
Is there a way of marking such casts as 'for sparse only' so
that the compiler does proper type checking.
(Clearly this isn't that relevant here as the cast could be (void **).)
Hmmm something should be checking that the type of the argument
to cmpxchg is 'pointer to "something the size of a pointer"'
Adding any kind of cast subverts that test.
David
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