From: Cong Wang <xiyou.wangcong@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Guillaume Nault <gnault@redhat.com>,
Vlad Buslov <vladbu@mellanox.com>,
Xin Long <lucien.xin@gmail.com>,
Pablo Neira Ayuso <pablo@netfilter.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] flow_dissector: work around stack frame size warning
Date: Fri, 29 May 2020 21:49:42 -0700 [thread overview]
Message-ID: <CAM_iQpWp7_CytqF9U4b7i7TYNytVPztpm-P+=9dBBdiy_nScLA@mail.gmail.com> (raw)
In-Reply-To: <20200529201413.397679-1-arnd@arndb.de>
On Fri, May 29, 2020 at 1:14 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> The fl_flow_key structure is around 500 bytes, so having two of them
> on the stack in one function now exceeds the warning limit after an
> otherwise correct change:
>
> net/sched/cls_flower.c:298:12: error: stack frame size of 1056 bytes in function 'fl_classify' [-Werror,-Wframe-larger-than=]
>
> I suspect the fl_classify function could be reworked to only have one
> of them on the stack and modify it in place, but I could not work out
> how to do that.
>
> As a somewhat hacky workaround, move one of them into an out-of-line
> function to reduce its scope. This does not necessarily reduce the stack
> usage of the outer function, but at least the second copy is removed
> from the stack during most of it and does not add up to whatever is
> called from there.
>
> I now see 552 bytes of stack usage for fl_classify(), plus 528 bytes
> for fl_mask_lookup().
>
> Fixes: 58cff782cc55 ("flow_dissector: Parse multiple MPLS Label Stack Entries")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
I think this is probably the quickest way to amend this warning,
so:
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Thanks.
next prev parent reply other threads:[~2020-05-30 4:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 20:13 [PATCH] flow_dissector: work around stack frame size warning Arnd Bergmann
2020-05-30 4:49 ` Cong Wang [this message]
2020-05-30 16:43 ` Guillaume Nault
2020-06-01 18:52 ` David Miller
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