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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_bl.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_bl.h')
-rw-r--r--include/linux/list_bl.h5
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
index 2eb88556c5c5..8132214e8efd 100644
--- a/include/linux/list_bl.h
+++ b/include/linux/list_bl.h
@@ -93,9 +93,10 @@ static inline void __hlist_bl_del(struct hlist_bl_node *n)
LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
/* pprev may be `first`, so be careful not to lose the lock bit */
- *pprev = (struct hlist_bl_node *)
+ WRITE_ONCE(*pprev,
+ (struct hlist_bl_node *)
((unsigned long)next |
- ((unsigned long)*pprev & LIST_BL_LOCKMASK));
+ ((unsigned long)*pprev & LIST_BL_LOCKMASK)));
if (next)
next->pprev = pprev;
}