linux-kernel - Re: [PATCH 2/3] mm: introduce VM_BUG_ON

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Message-ID: <541223F9.2090500@oracle.com>
Date:	Thu, 11 Sep 2014 18:36:41 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	kirill.shutemov@...ux.intel.com, khlebnikov@...nvz.org,
	riel@...hat.com, mgorman@...e.de, n-horiguchi@...jp.nec.com,
	mhocko@...e.cz, hughd@...gle.com, vbabka@...e.cz,
	walken@...gle.com, minchan@...nel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/3] mm: introduce VM_BUG_ON_MM

On 09/11/2014 05:16 PM, Andrew Morton wrote:
> On Sat,  6 Sep 2014 15:38:45 -0400 Sasha Levin <sasha.levin@...cle.com> wrote:
> 
>> Very similar to VM_BUG_ON_PAGE and VM_BUG_ON_VMA, dump struct_mm
>> when the bug is hit.
>>
>> ...
>>
>> +void dump_mm(const struct mm_struct *mm)
>> +{
>> +	printk(KERN_ALERT
> 
> I'm not sure why we should use KERN_ALERT here - KERN_EMERG is for
> "system is unusable", which is a fair descrition of a post-BUG kernel,
> yes?

Yes. I was following suit with dump_page and assumed there's a good reasoning
behind KERN_ALERT.

>> +		"mm %p mmap %p seqnum %d task_size %lu\n"
>> +#ifdef CONFIG_MMU
>> +		"get_unmapped_area %p\n"
>> +#endif
> 
> This printk is rather hilarious.  I can't think of a better way apart
> from a great string of individual printks.
> 
> And maybe we should use individual printks - dump_mm() presently uses
> 114 bytes of stack for that printk and that's somewhat of a concern
> considering the situations when it will be called.
> 
> 
> How's this look?

Works for me.


Thanks,
Sasha

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