From: Mikulas Patocka mpatocka@redhat.com
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@redhat.com Cc: stable@vger.kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rds/ib_recv.c | 1 + 1 file changed, 1 insertion(+)
--- a/net/rds/ib_recv.c +++ b/net/rds/ib_recv.c @@ -356,6 +356,7 @@ 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