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    Subject[PATCH AUTOSEL 5.5 294/542] mlx5: work around high stack usage with gcc
    Date
    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
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