From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
commit 9f414eb409daf4f778f011cf8266d36896bb930b upstream.
The functions clear_bit and set_bit do not imply a memory barrier, thus it
may be possible that the waitqueue_active function (which does not take
any locks) is moved before clear_bit and it could miss a wakeup event.
Fix this bug by adding a memory barrier after clear_bit.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/rds/ib_recv.c | 1 +
1 file changed, 1 insertion(+)
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -363,6 +363,7 @@ static int acquire_refill(struct rds_con
static void release_refill(struct rds_connection *conn)
{
clear_bit(RDS_RECV_REFILL, &conn->c_flags);
+ smp_mb__after_atomic();
/* We don't use wait_on_bit()/wake_up_bit() because our waking is in a
* hot path and finding waiters is very rare. We don't want to walk
