linux-kernel - Re: [PATCH v3 09/17] memblock: make memblock_debug and related functionality private

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Message-ID: <20200819204848.GX752365@kernel.org>
Date:   Wed, 19 Aug 2020 23:48:48 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...nel.org>, Baoquan He <bhe@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@....de>, Daniel Axtens <dja@...ens.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Ingo Molnar <mingo@...hat.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Simek <monstr@...str.eu>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Russell King <linux@...linux.org.uk>,
        Stafford Horne <shorne@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        clang-built-linux@...glegroups.com,
        iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-c6x-dev@...ux-c6x.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, linuxppc-dev@...ts.ozlabs.org,
        openrisc@...ts.librecores.org, sparclinux@...r.kernel.org,
        uclinux-h8-devel@...ts.sourceforge.jp, x86@...nel.org
Subject: Re: [PATCH v3 09/17] memblock: make memblock_debug and related
 functionality private

On Wed, Aug 19, 2020 at 12:24:05PM -0700, Andrew Morton wrote:
> On Tue, 18 Aug 2020 18:16:26 +0300 Mike Rapoport <rppt@...nel.org> wrote:
> 
> > From: Mike Rapoport <rppt@...ux.ibm.com>
> > 
> > The only user of memblock_dbg() outside memblock was s390 setup code and it
> > is converted to use pr_debug() instead.
> > This allows to stop exposing memblock_debug and memblock_dbg() to the rest
> > of the kernel.
> > 
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -137,7 +137,10 @@ struct memblock_type physmem = {
> >  	     i < memblock_type->cnt;					\
> >  	     i++, rgn = &memblock_type->regions[i])
> >  
> > -int memblock_debug __initdata_memblock;
> > +#define memblock_dbg(fmt, ...) \
> > +	if (memblock_debug) printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> > +
> 
> checkpatch doesn't like this much.
> 
> ERROR: Macros starting with if should be enclosed by a do - while loop to avoid possible if/else logic defects
> #101: FILE: mm/memblock.c:140:
> +#define memblock_dbg(fmt, ...) \
> +	if (memblock_debug) printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> 
> WARNING: Prefer [subsystem eg: netdev]_info([subsystem]dev, ... then dev_info(dev, ... then pr_info(...  to printk(KERN_INFO ...
> #102: FILE: mm/memblock.c:141:
> +	if (memblock_debug) printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> 
> ERROR: trailing statements should be on next line
> #102: FILE: mm/memblock.c:141:
> +	if (memblock_debug) printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> 
> 
> The first one is significant:
> 
> 	if (foo)
> 		memblock_dbg(...);
> 	else
> 		save_the_world();
> 
> could end up inadvertently destroying the planet.

Well, it didn't till now ;-)

> This?
> 
> --- a/mm/memblock.c~memblock-make-memblock_debug-and-related-functionality-private-fix
> +++ a/mm/memblock.c
> @@ -137,8 +137,11 @@ struct memblock_type physmem = {
>  	     i < memblock_type->cnt;					\
>  	     i++, rgn = &memblock_type->regions[i])
>  
> -#define memblock_dbg(fmt, ...) \
> -	if (memblock_debug) printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> +#define memblock_dbg(fmt, ...)						\
> +	do {								\
> +		if (memblock_debug)					\
> +			pr_info(fmt, ##__VA_ARGS__);			\
> +	} while (0)

Sure, thanks!

>  static int memblock_debug __initdata_memblock;
>  static bool system_has_some_mirror __initdata_memblock = false;
> _
> 

-- 
Sincerely yours,
Mike.