linux-kernel - Re: [PATCH] init: consolidate trap

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Message-ID: <44bdf1f1-117d-0f10-fc59-9edd32d1ad61@csgroup.eu>
Date:   Wed, 14 Apr 2021 11:10:42 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Russell King <linux@...linux.org.uk>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Brian Cain <bcain@...eaurora.org>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>
Cc:     uclinux-h8-devel@...ts.sourceforge.jp,
        linux-parisc@...r.kernel.org, linux-hexagon@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org,
        openrisc@...ts.librecores.org, Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org,
        linux-snps-arc@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] init: consolidate trap_init()



Le 14/04/2021 à 10:58, Jisheng Zhang a écrit :
> Many architectures implement the trap_init() as NOP, since there is
> no such default for trap_init(), this empty stub is duplicated among
> these architectures. Provide a generic but weak NOP implementation
> to drop the empty stubs of trap_init() in these architectures.

You define the weak function in the __init section.

Most but not all architectures had it in __init section.

And the remaining ones may not be defined in __init section. For instance look at the one in alpha 
architecture.

Have you checked that it is not a problem ? It would be good to say something about it in the commit 
description.


> 
> Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
> ---
>   arch/arc/kernel/traps.c      |  5 -----
>   arch/arm/kernel/traps.c      |  5 -----
>   arch/h8300/kernel/traps.c    | 13 -------------
>   arch/hexagon/kernel/traps.c  |  4 ----
>   arch/nds32/kernel/traps.c    |  5 -----
>   arch/nios2/kernel/traps.c    |  5 -----
>   arch/openrisc/kernel/traps.c |  5 -----
>   arch/parisc/kernel/traps.c   |  4 ----
>   arch/powerpc/kernel/traps.c  |  5 -----
>   arch/riscv/kernel/traps.c    |  5 -----
>   arch/um/kernel/trap.c        |  4 ----
>   init/main.c                  |  2 ++
>   12 files changed, 2 insertions(+), 60 deletions(-)
> 
> diff --git a/init/main.c b/init/main.c
> index 53b278845b88..4bdbe2928530 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -790,6 +790,8 @@ static inline void initcall_debug_enable(void)
>   }
>   #endif
>   
> +void __init __weak trap_init(void) { }
> +

I think in a C file we don't try to save space as much as in a header file.

I would prefer something like:


void __init __weak trap_init(void)
{
}


>   /* Report memory auto-initialization states for this boot. */
>   static void __init report_meminit(void)
>   {
>