From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
The sparse checking for rcu_assign_pointer() was recently upgraded
to reject non-__kernel address spaces. This also rejects __rcu,
which is almost always the right thing to do. However, the use in
notifier_chain_unregister() is legitimate: It is deleting an element
from an RCU-protected list, and all elements of this list are already
visible to caller.
This commit therefore silences this false positive by laundering the
pointer using ACCESS_ONCE() as suggested by Eric Dumazet and Josh
Triplett.
Reported-by: kbuild test robot <fengguang...@intel.com>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
kernel/notifier.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/notifier.c b/kernel/notifier.c
index 2d5cc4ccff7f..197eb70805a4 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -51,7 +51,8 @@ static int notifier_chain_unregister(struct notifier_block
**nl,
{
while ((*nl) != NULL) {
if ((*nl) == n) {
- rcu_assign_pointer(*nl, n->next);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(*nl) = n->next;
return 0;
}
nl = &((*nl)->next);
--
1.8.1.5
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