Paul E. McKenney b1a07165be rcu: Create an unrcu_pointer() to remove __rcu from a pointer ...

[ Upstream commit 76c8eaafe4f061f3790112842a2fbb297e4bea88 ]

The xchg() and cmpxchg() functions are sometimes used to carry out RCU
updates.  Unfortunately, this can result in sparse warnings for both
the old-value and new-value arguments, as well as for the return value.
The arguments can be dealt with using RCU_INITIALIZER():

	old_p = xchg(&p, RCU_INITIALIZER(new_p));

But a sparse warning still remains due to assigning the __rcu pointer
returned from xchg to the (most likely) non-__rcu pointer old_p.

This commit therefore provides an unrcu_pointer() macro that strips
the __rcu.  This macro can be used as follows:

	old_p = unrcu_pointer(xchg(&p, RCU_INITIALIZER(new_p)));

Reported-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Stable-dep-of: 5f35a624c1e3 ("drm/nouveau/fence:: fix warning directly dereferencing a rcu pointer")
Signed-off-by: Sasha Levin <sashal@kernel.org>

2024-01-25 14:37:46 -08:00

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