write in 30M

hc

2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc

 kernel/include/linux/list_nulls.h
..
..
@@ -56,11 +56,33 @@
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 	return ((unsigned long)ptr) >> 1;
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 }
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+/**
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+ * hlist_nulls_unhashed - Has node been removed and reinitialized?
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+ * @h: Node to be checked
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+ *
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+ * Not that not all removal functions will leave a node in unhashed state.
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+ * For example, hlist_del_init_rcu() leaves the node in unhashed state,
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+ * but hlist_nulls_del() does not.
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+ */
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 static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h)
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 {
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 	return !h->pprev;
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 }
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+/**
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+ * hlist_nulls_unhashed_lockless - Has node been removed and reinitialized?
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+ * @h: Node to be checked
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+ *
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+ * Not that not all removal functions will leave a node in unhashed state.
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+ * For example, hlist_del_init_rcu() leaves the node in unhashed state,
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+ * but hlist_nulls_del() does not.  Unlike hlist_nulls_unhashed(), this
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+ * function may be used locklessly.
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+ */
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+static inline int hlist_nulls_unhashed_lockless(const struct hlist_nulls_node *h)
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+{
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+	return !READ_ONCE(h->pprev);
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+}
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+
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 static inline int hlist_nulls_empty(const struct hlist_nulls_head *h)
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 {
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 	return is_a_nulls(READ_ONCE(h->first));