Re: [PATCH 2/5] do_div(): generic optimization for constant divisor on 32-bit machines

From: Arnd Bergmann
Date: Tue Nov 03 2015 - 04:16:31 EST

On Tuesday 03 November 2015 13:32:17 kbuild test robot wrote:
> net/can/bcm.c: In function 'bcm_proc_show':
> >> net/can/bcm.c:223:1: warning: the frame size of 1156 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> }

Interesting, that is a lot of stack for a function that only has a couple
of local variables:

#define IFNAMSIZ 16
char ifname[IFNAMSIZ];
struct sock *sk = (struct sock *)m->private;
struct bcm_sock *bo = bcm_sk(sk);
struct bcm_op *op;

This is a parisc-allyesconfig kernel, so I assume that CONFIG_PROFILE_ALL_BRANCHES
is on, which instruments every 'if' in the kernel. If that causes problems,
we could decide to disable the do_div optimization whenever CONFIG_PROFILE_ALL_BRANCHES
is enabled.

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