net/mlx4: fix build with -fno-common

[ upstream commit a5e5af7 ]

The variable storages of the same name are merged together
if compiled with -fcommon. This is the default.
This default behaviour allows to declare a variable in a header file and
share the variable in every .o binaries thanks to merge at link-time.

In the case of dlopen linking of the glue library, the pointer mlx4_glue
is referencing the glue functions struct and is set after calling
dlopen.

If compiling with -fno-common (default in GCC 10), the variables must be
declared as extern to avoid multiple re-definitions.
In case the glue layer is split in glue library, the variable mlx4_glue
needs to have its own storage for the rest of the PMD.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@mellanox.com>

drivers/net/mlx4/mlx4.c

@@ -48,6 +48,10 @@
 #include "mlx4_rxtx.h"
 #include "mlx4_utils.h"
 
+#ifdef MLX4_GLUE
+const struct mlx4_glue *mlx4_glue;
+#endif
+
 struct mlx4_dev_list mlx4_mem_event_cb_list =
 	LIST_HEAD_INITIALIZER(mlx4_mem_event_cb_list);
 

drivers/net/mlx4/mlx4_glue.h

@@ -84,6 +84,6 @@ struct mlx4_glue {
 				   void *attr);
 };
 
-const struct mlx4_glue *mlx4_glue;
+extern const struct mlx4_glue *mlx4_glue;
 
 #endif /* MLX4_GLUE_H_ */

drivers/net/mlx4/mlx4_rxtx.h

@@ -120,7 +120,7 @@ struct txq {
 
 /* mlx4_rxq.c */
 
-uint8_t mlx4_rss_hash_key_default[MLX4_RSS_HASH_KEY_SIZE];
+extern uint8_t mlx4_rss_hash_key_default[MLX4_RSS_HASH_KEY_SIZE];
 int mlx4_rss_init(struct mlx4_priv *priv);
 void mlx4_rss_deinit(struct mlx4_priv *priv);
 struct mlx4_rss *mlx4_rss_get(struct mlx4_priv *priv, uint64_t fields,