net/virtio: fix variable assignment in helper macro

Inside Macro ASSIGN_UNLESS_EQUAL(var, val), assignment to var is always
failing as assignment done using var_ having local scope only.
This leads to TX packets not going out and found broken due to cleanup
malfunctioning. This patch fixes the wrong variable assignment.

Fixes: 57f90f894588 ("net/virtio: reuse packed ring functions")
Cc: stable@dpdk.org
Signed-off-by: Vipul Ashri <vipul.ashri@oracle.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 105a9c0..6ed5064 100644 (file)
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -607,10 +607,10 @@ virtqueue_notify(struct virtqueue *vq)
 
 /* avoid write operation when necessary, to lessen cache issues */
 #define ASSIGN_UNLESS_EQUAL(var, val) do {     \
-       typeof(var) var_ = (var);               \
-       typeof(val) val_ = (val);               \
-       if ((var_) != (val_))                   \
-               (var_) = (val_);                \
+       typeof(var) *const var_ = &(var);       \
+       typeof(val)  const val_ = (val);        \
+       if (*var_ != val_)                      \
+               *var_ = val_;                   \
 } while (0)
 
 #define virtqueue_clear_net_hdr(hdr) do {              \