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| author |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-09-20 17:03:16 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-11-23 10:37:35 -0800 |
| commit | 1658d35ead5d8dd76f2b2d6ad0e32c08d123faa2 (patch) | |
| tree | b237b079d8c057cb77e54f7e21baec00196b448f | |
| parent | list: Use WRITE_ONCE() when adding to lists and hlists (diff) | |
| download | wireguard-linux-1658d35ead5d8dd76f2b2d6ad0e32c08d123faa2.tar.xz wireguard-linux-1658d35ead5d8dd76f2b2d6ad0e32c08d123faa2.zip | |
list: Use READ_ONCE() when testing for empty lists
Most of the list-empty-check macros (list_empty(), hlist_empty(),
hlist_bl_empty(), hlist_nulls_empty(), and hlist_nulls_empty()) use
an unadorned load to check the list header. Given that these macros
are sometimes invoked without the protection of a lock, this is
not sufficient. This commit therefore adds READ_ONCE() calls to
them. This commit does not touch llist_empty() because it already
has the needed ACCESS_ONCE().
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| -rw-r--r-- | include/linux/list.h | 4 | ||||
| -rw-r--r-- | include/linux/list_bl.h | 2 | ||||
| -rw-r--r-- | include/linux/list_nulls.h | 2 |
3 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index d7e31fe398b3..06c2d887a918 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -186,7 +186,7 @@ static inline int list_is_last(const struct list_head *list, */ static inline int list_empty(const struct list_head *head) { - return head->next == head; + return READ_ONCE(head->next) == head; } /** @@ -608,7 +608,7 @@ static inline int hlist_unhashed(const struct hlist_node *h) static inline int hlist_empty(const struct hlist_head *h) { - return !h->first; + return !READ_ONCE(h->first); } static inline void __hlist_del(struct hlist_node *n) diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h index 8132214e8efd..ee7229a6c06a 100644 --- a/include/linux/list_bl.h +++ b/include/linux/list_bl.h @@ -70,7 +70,7 @@ static inline void hlist_bl_set_first(struct hlist_bl_head *h, static inline int hlist_bl_empty(const struct hlist_bl_head *h) { - return !((unsigned long)h->first & ~LIST_BL_LOCKMASK); + return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK); } static inline void hlist_bl_add_head(struct hlist_bl_node *n, diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h index 444d2b1313bd..b01fe1009084 100644 --- a/include/linux/list_nulls.h +++ b/include/linux/list_nulls.h @@ -57,7 +57,7 @@ static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h) static inline int hlist_nulls_empty(const struct hlist_nulls_head *h) { - return is_a_nulls(h->first); + return is_a_nulls(READ_ONCE(h->first)); } static inline void hlist_nulls_add_head(struct hlist_nulls_node *n, |