rcu: Provide counterpart to rcu_dereference() for non-RCU situations
Although rcu_dereference() and friends can be used in situations where object lifetimes are being managed by something other than RCU, the resulting sparse and lockdep-RCU noise can be annoying. This commit therefore supplies a lockless_dereference(), which provides the protection for dereferences without the RCU-related debugging noise. Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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@ -616,6 +616,21 @@ static inline void rcu_preempt_sleep_check(void)
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*/
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*/
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#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
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#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
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/**
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* lockless_dereference() - safely load a pointer for later dereference
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* @p: The pointer to load
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*
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* Similar to rcu_dereference(), but for situations where the pointed-to
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* object's lifetime is managed by something other than RCU. That
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* "something other" might be reference counting or simple immortality.
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*/
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#define lockless_dereference(p) \
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({ \
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typeof(p) _________p1 = ACCESS_ONCE(p); \
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smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
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(_________p1); \
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})
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/**
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/**
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* rcu_assign_pointer() - assign to RCU-protected pointer
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* rcu_assign_pointer() - assign to RCU-protected pointer
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* @p: pointer to assign to
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* @p: pointer to assign to
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