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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-09-18 08:45:22 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-10-06 11:16:42 -0700
commit7f5f873c6a0772970d5fee1f364231207051ecd8 (patch)
treeca06a26b0a485a63cf42417a12dea443a0df103c /include/linux/list_nulls.h
parente62e3f620ba8d437f4998441fc11cf3dc9d466d1 (diff)
rculist: Use WRITE_ONCE() when deleting from reader-visible list
The various RCU list-deletion macros (list_del_rcu(), hlist_del_init_rcu(), hlist_del_rcu(), hlist_bl_del_init_rcu(), hlist_bl_del_rcu(), hlist_nulls_del_init_rcu(), and hlist_nulls_del_rcu()) do plain stores into the ->next pointer of the preceding list elemment. Unfortunately, the compiler is within its rights to (for example) use byte-at-a-time writes to update the pointer, which would fatally confuse concurrent readers. This patch therefore adds the needed WRITE_ONCE() macros. KernelThreadSanitizer (KTSAN) reported the __hlist_del() issue, which is a problem when __hlist_del() is invoked by hlist_del_rcu(). Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'include/linux/list_nulls.h')
-rw-r--r--include/linux/list_nulls.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
index f266661d2666..444d2b1313bd 100644
--- a/include/linux/list_nulls.h
+++ b/include/linux/list_nulls.h
@@ -76,7 +76,8 @@ static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
{
struct hlist_nulls_node *next = n->next;
struct hlist_nulls_node **pprev = n->pprev;
- *pprev = next;
+
+ WRITE_ONCE(*pprev, next);
if (!is_a_nulls(next))
next->pprev = pprev;
}