[PATCH 4.20 024/183] pvcalls-back: set -ENOTCONN in pvcalls_conn_back_read

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit e6587cdbd732eacb4c7ce592ed46f7bbcefb655f ]

When a connection is closing we receive on pvcalls_sk_state_change
notification. Instead of setting the connection as closed immediately
(-ENOTCONN), let's read one more time from it: pvcalls_conn_back_read
will set the connection as closed when necessary.

That way, we avoid races between pvcalls_sk_state_change and
pvcalls_back_ioworker.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/xen/pvcalls-back.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index 2e5d845b50914..71b628774c6fb 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -160,9 +160,10 @@ static void pvcalls_conn_back_read(void *opaque)
 
 	/* write the data, then modify the indexes */
 	virt_wmb();
-	if (ret < 0)
+	if (ret < 0) {
+		atomic_set(&map->read, 0);
 		intf->in_error = ret;
-	else
+	} else
 		intf->in_prod = prod + ret;
 	/* update the indexes, then notify the other end */
 	virt_wmb();
@@ -288,7 +289,7 @@ static void pvcalls_sk_state_change(struct sock *sock)
 		return;
 
 	intf = map->ring;
-	intf->in_error = -ENOTCONN;
+	atomic_inc(&map->read);
 	notify_remote_via_irq(map->irq);
 }
 
-- 
2.19.1