| Message ID | 20200104215156.689245-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | mlx5: work around high stack usage with gcc | expand |
From: Arnd Bergmann <arnd@arndb.de> Date: Sat, 4 Jan 2020 22:51:44 +0100 > 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> Saeed, please take this. Thank you.
On Mon, 2020-01-06 at 13:34 -0800, David Miller wrote: > From: Arnd Bergmann <arnd@arndb.de> > Date: Sat, 4 Jan 2020 22:51:44 +0100 > > > 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> > > Saeed, please take this. > > Thank you. > Applied to net-next-mlx5 will submit to net-next later today. Thanks !
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c index 9f09253f9f46..a05158472ed1 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(); } } }
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> --- drivers/net/ethernet/mellanox/mlx5/core/en_stats.c | 3 +++ 1 file changed, 3 insertions(+)