linux-kernel - Re: [PATCH linux-next] x86/mm: Fix compile warning in remove

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Message-ID: <511214A3.6060201@cn.fujitsu.com>
Date:	Wed, 06 Feb 2013 16:30:27 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Shuah Khan <shuah.khan@...com>,
	Andrew Morton <akpm@...ux-foundation.org>, tglx@...utronix.de,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	yinghai@...nel.org, wency@...fujitsu.com,
	linux-kernel@...r.kernel.org, x86@...nel.org, shuahkhan@...il.com
Subject: Re: [PATCH linux-next] x86/mm: Fix compile warning in remove_pagetable()

On 02/06/2013 04:27 PM, David Rientjes wrote:
> On Tue, 5 Feb 2013, Shuah Khan wrote:
>
>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>> index 67bad4b..ed78400 100644
>> --- a/arch/x86/mm/init_64.c
>> +++ b/arch/x86/mm/init_64.c
>> @@ -987,7 +987,7 @@ remove_pud_table(pud_t *pud_start, unsigned long addr, unsigned long end,
>>   static void __meminit
>>   remove_pagetable(unsigned long start, unsigned long end, bool direct)
>>   {
>> -	unsigned long next;
>> +	unsigned long next = pgd_addr_end(start, end);
>>   	pgd_t *pgd;
>>   	pud_t *pud;
>>   	bool pgd_changed = false;
>
> This isn't enough, there's a potential for an infinite loop if
> !pgd_present() is ever true in the iteration since "next" remains
> constant.  Theoretical, maybe.
>
> I think it's better to just set next before checking for !pgd_present() in
> the iteration so it's clear what's happening.

Yes, Andrew's patch just fixed it like this. :)

Thanks. :)

> Or, even better, change
> this into the standard do-while loop that everything else uses.
>

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