[PATCH 5.4 188/344] mlx5: work around high stack usage with gcc

Greg Kroah-Hartman
2020-02-21T08:33:20Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 42ae1a5c76691928ed217c7e40269db27f5225e9 ]

In some configurations, gcc tries too hard to optimize this code:

drivers/net/ethernet/mellanox/mlx5/core/en_stats.c: In function 'mlx5e_grp_sw_update_stats':
drivers/net/ethernet/mellanox/mlx5/core/en_stats.c:302:1: error: the frame size of 1336 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

As was stated in the bug report, the reason is that gcc runs into a corner
case in the register allocator that is rather hard to fix in a good way.

As there is an easy way to work around it, just add a comment and the
barrier that stops gcc from trying to overoptimize the function.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92657
Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/mellanox/mlx5/core/en_stats.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
index 9f09253f9f466..a05158472ed11 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
@@ -297,6 +297,9 @@ static void mlx5e_grp_sw_update_stats(struct mlx5e_priv *priv)
s->tx_tls_drop_bypass_req += sq_stats->tls_drop_bypass_req;
#endif
s->tx_cqes += sq_stats->cqes;
+
+ /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92657 */
+ barrier();
}
}
}
--
2.20.1