linux-kernel - Re: [PATCH] mlx5: work around high stack usage with gcc

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Message-ID: <057f4159f41b1d470d47a375435bc5afcb2c0261.camel@mellanox.com>
Date:   Mon, 6 Jan 2020 21:59:30 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "davem@...hat.com" <davem@...hat.com>,
        "arnd@...db.de" <arnd@...db.de>
CC:     Aya Levin <ayal@...lanox.com>, Shay Agroskin <shayag@...lanox.com>,
        Moshe Shemesh <moshe@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Maxim Mikityanskiy <maximmi@...lanox.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "leon@...nel.org" <leon@...nel.org>,
        "adhemerval.zanella@...aro.org" <adhemerval.zanella@...aro.org>
Subject: Re: [PATCH] mlx5: work around high stack usage with gcc

On Mon, 2020-01-06 at 13:34 -0800, David Miller wrote:
> From: Arnd Bergmann <arnd@...db.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@...aro.org>
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> Saeed, please take this.
> 
> Thank you.
> 

Applied to net-next-mlx5

will submit to net-next later today.

Thanks !