Re: [dpdk-stable] [dpdk-dev] [PATCH 0/3] mlx: fix build with -fno-common (gcc 10)

Re: [dpdk-stable] [dpdk-dev] [PATCH 0/3] mlx: fix build with -fno-common (gcc 10)

[Thomas Monjalon]

17/03/2020 09:34, Matan Azrad:
>  From:  Thomas Monjalon
> > In GCC 10, -fno-common will be the default.
> > There are 2 ways of solving issues:
> >   - add -fcommon
> >   - stop allocating variables in .h files
> > 
> > In this patchset, the variables are declared extern, because it is cleaner
> > anyway.
> 
> Series-acked-by: Matan Azrad <matan@mellanox.com>
> 
> > Thomas Monjalon (3):
> >   common/mlx5: split glue initialization
> >   common/mlx5: fix build with -fno-common
> >   net/mlx4: fix build with -fno-common

It seems these patches are also fixing usage of glue dlopen
with PMD as shared library.
We should add Cc: stable@dpdk.org and identify a root cause.

[dpdk-stable] [PATCH v2 2/3] common/mlx5: fix build with -fno-common

[Thomas Monjalon]

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 mlx5_glue
is referencing the glue functions struct and is set after calling dlopen.

If compiling with -fno-common (default in GCC 10), the variable
must be declared as extern to avoid multiple re-definitions.
In case the glue layer is split in glue library, the variable mlx5_glue
needs to have its own storage for the rest of the PMD.

Cc: stable@dpdk.org

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@mellanox.com>
---
 drivers/common/mlx5/mlx5_common.c | 3 +++
 drivers/common/mlx5/mlx5_glue.h   | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/common/mlx5/mlx5_common.c b/drivers/common/mlx5/mlx5_common.c
index 9a30e6e0aa..98a82c262f 100644
--- a/drivers/common/mlx5/mlx5_common.c
+++ b/drivers/common/mlx5/mlx5_common.c
@@ -18,6 +18,9 @@
 
 int mlx5_common_logtype;
 
+#ifdef MLX5_GLUE
+const struct mlx5_glue *mlx5_glue;
+#endif
 
 /**
  * Get PCI information by sysfs device path.
diff --git a/drivers/common/mlx5/mlx5_glue.h b/drivers/common/mlx5/mlx5_glue.h
index 6238b43946..29678623e4 100644
--- a/drivers/common/mlx5/mlx5_glue.h
+++ b/drivers/common/mlx5/mlx5_glue.h
@@ -300,6 +300,6 @@ struct mlx5_glue {
 			 size_t event_resp_len);
 };
 
-const struct mlx5_glue *mlx5_glue;
+extern const struct mlx5_glue *mlx5_glue;
 
 #endif /* MLX5_GLUE_H_ */
-- 
2.26.0

[dpdk-stable] [PATCH v2 3/3] net/mlx4: fix build with -fno-common

[Thomas Monjalon]

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.

Cc: stable@dpdk.org

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@mellanox.com>
---
 drivers/net/mlx4/mlx4.c      | 4 ++++
 drivers/net/mlx4/mlx4_glue.h | 2 +-
 drivers/net/mlx4/mlx4_rxtx.h | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c
index 339a4d3ab6..ee15f28dff 100644
--- a/drivers/net/mlx4/mlx4.c
+++ b/drivers/net/mlx4/mlx4.c
@@ -49,6 +49,10 @@
 #include "mlx4_rxtx.h"
 #include "mlx4_utils.h"
 
+#ifdef MLX4_GLUE
+const struct mlx4_glue *mlx4_glue;
+#endif
+
 static const char *MZ_MLX4_PMD_SHARED_DATA = "mlx4_pmd_shared_data";
 
 /* Shared memory between primary and secondary processes. */
diff --git a/drivers/net/mlx4/mlx4_glue.h b/drivers/net/mlx4/mlx4_glue.h
index 668ca86700..5d9e985495 100644
--- a/drivers/net/mlx4/mlx4_glue.h
+++ b/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_ */
diff --git a/drivers/net/mlx4/mlx4_rxtx.h b/drivers/net/mlx4/mlx4_rxtx.h
index 8baf33fa94..9de6c59411 100644
--- a/drivers/net/mlx4/mlx4_rxtx.h
+++ b/drivers/net/mlx4/mlx4_rxtx.h
@@ -124,7 +124,7 @@ 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,
-- 
2.26.0

[dpdk-stable] [PATCH v3 2/3] common/mlx5: fix build with -fno-common

[Thomas Monjalon]

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 mlx5_glue
is referencing the glue functions struct and is set after calling dlopen.

If compiling with -fno-common (default in GCC 10), the variable
must be declared as extern to avoid multiple re-definitions.
In case the glue layer is split in glue library, the variable mlx5_glue
needs to have its own storage for the rest of the PMD.

Cc: stable@dpdk.org

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@mellanox.com>
---
 drivers/common/mlx5/mlx5_common.c | 3 +++
 drivers/common/mlx5/mlx5_glue.h   | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/common/mlx5/mlx5_common.c b/drivers/common/mlx5/mlx5_common.c
index d8c01a5d14..42610459f7 100644
--- a/drivers/common/mlx5/mlx5_common.c
+++ b/drivers/common/mlx5/mlx5_common.c
@@ -18,6 +18,9 @@
 
 int mlx5_common_logtype;
 
+#ifdef MLX5_GLUE
+const struct mlx5_glue *mlx5_glue;
+#endif
 
 /**
  * Get PCI information by sysfs device path.
diff --git a/drivers/common/mlx5/mlx5_glue.h b/drivers/common/mlx5/mlx5_glue.h
index 6238b43946..29678623e4 100644
--- a/drivers/common/mlx5/mlx5_glue.h
+++ b/drivers/common/mlx5/mlx5_glue.h
@@ -300,6 +300,6 @@ struct mlx5_glue {
 			 size_t event_resp_len);
 };
 
-const struct mlx5_glue *mlx5_glue;
+extern const struct mlx5_glue *mlx5_glue;
 
 #endif /* MLX5_GLUE_H_ */
-- 
2.26.0

[dpdk-stable] [PATCH v3 3/3] net/mlx4: fix build with -fno-common

[Thomas Monjalon]

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.

Cc: stable@dpdk.org

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Matan Azrad <matan@mellanox.com>
---
 drivers/net/mlx4/mlx4.c      | 4 ++++
 drivers/net/mlx4/mlx4_glue.h | 2 +-
 drivers/net/mlx4/mlx4_rxtx.h | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c
index 8e298788af..5d7202720b 100644
--- a/drivers/net/mlx4/mlx4.c
+++ b/drivers/net/mlx4/mlx4.c
@@ -49,6 +49,10 @@
 #include "mlx4_rxtx.h"
 #include "mlx4_utils.h"
 
+#ifdef MLX4_GLUE
+const struct mlx4_glue *mlx4_glue;
+#endif
+
 static const char *MZ_MLX4_PMD_SHARED_DATA = "mlx4_pmd_shared_data";
 
 /* Shared memory between primary and secondary processes. */
diff --git a/drivers/net/mlx4/mlx4_glue.h b/drivers/net/mlx4/mlx4_glue.h
index 668ca86700..5d9e985495 100644
--- a/drivers/net/mlx4/mlx4_glue.h
+++ b/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_ */
diff --git a/drivers/net/mlx4/mlx4_rxtx.h b/drivers/net/mlx4/mlx4_rxtx.h
index 8baf33fa94..9de6c59411 100644
--- a/drivers/net/mlx4/mlx4_rxtx.h
+++ b/drivers/net/mlx4/mlx4_rxtx.h
@@ -124,7 +124,7 @@ 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,
-- 
2.26.0