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list: Use WRITE_ONCE() when adding to lists and hlists
Code that does lockless emptiness testing of non-RCU lists is relying on the list-addition code to write the list head's ->next pointer atomically. This commit therefore adds WRITE_ONCE() to list-addition pointer stores that could affect the head's ->next pointer. Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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6cf1008122
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1c97be677f
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@ -42,7 +42,7 @@ static inline void __list_add(struct list_head *new,
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next->prev = new;
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next->prev = new;
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new->next = next;
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new->next = next;
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new->prev = prev;
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new->prev = prev;
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prev->next = new;
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WRITE_ONCE(prev->next, new);
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}
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}
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#else
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#else
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extern void __list_add(struct list_head *new,
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extern void __list_add(struct list_head *new,
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@ -642,7 +642,7 @@ static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
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n->next = first;
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n->next = first;
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if (first)
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if (first)
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first->pprev = &n->next;
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first->pprev = &n->next;
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h->first = n;
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WRITE_ONCE(h->first, n);
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n->pprev = &h->first;
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n->pprev = &h->first;
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}
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}
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@ -653,14 +653,14 @@ static inline void hlist_add_before(struct hlist_node *n,
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n->pprev = next->pprev;
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n->pprev = next->pprev;
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n->next = next;
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n->next = next;
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next->pprev = &n->next;
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next->pprev = &n->next;
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*(n->pprev) = n;
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WRITE_ONCE(*(n->pprev), n);
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}
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}
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static inline void hlist_add_behind(struct hlist_node *n,
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static inline void hlist_add_behind(struct hlist_node *n,
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struct hlist_node *prev)
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struct hlist_node *prev)
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{
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{
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n->next = prev->next;
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n->next = prev->next;
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prev->next = n;
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WRITE_ONCE(prev->next, n);
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n->pprev = &prev->next;
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n->pprev = &prev->next;
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if (n->next)
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if (n->next)
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@ -37,7 +37,7 @@ void __list_add(struct list_head *new,
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next->prev = new;
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next->prev = new;
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new->next = next;
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new->next = next;
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new->prev = prev;
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new->prev = prev;
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prev->next = new;
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WRITE_ONCE(prev->next, new);
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}
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}
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EXPORT_SYMBOL(__list_add);
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EXPORT_SYMBOL(__list_add);
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