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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-09-18 08:45:22 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-10-06 11:16:42 -0700 |
| commit | 7f5f873c6a0772970d5fee1f364231207051ecd8 (patch) | |
| tree | ca06a26b0a485a63cf42417a12dea443a0df103c /include/linux/list_bl.h | |
| parent | e62e3f620ba8d437f4998441fc11cf3dc9d466d1 (diff) | |
| download | lwn-7f5f873c6a0772970d5fee1f364231207051ecd8.tar.gz lwn-7f5f873c6a0772970d5fee1f364231207051ecd8.zip | |
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.h | 5 |
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; } |