linux-kernel - Re: [PATCH]: bunzip2: Fix warning in get_next

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Message-ID: <4BF81D64.8000700@redhat.com>
Date:	Sat, 22 May 2010 14:07:32 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	linux-kernel@...r.kernel.org, stable@...nel.org,
	phillip@...gher.demon.co.uk, alain@...ff.lu, hpa@...or.com
Subject: Re: [PATCH]: bunzip2: Fix warning in get_next_block()



On 05/22/2010 10:07 AM, Al Viro wrote:
> On Sat, May 22, 2010 at 10:04:07AM -0400, Prarit Bhargava wrote:
>    
>> Fix checkstack compile warning in get_next_block():
>>
>> lib/decompress_bunzip2.c: In function `get_next_block':
>> lib/decompress_bunzip2.c:511: warning: the frame size of 1920 bytes is larger than 1024 bytes
>>      
>
>    
>>   	int dbufCount, nextSym, dbufSize, groupCount, selector,
>> -		i, j, k, t, runPos, symCount, symTotal, nSelectors,
>> -		byteCount[256];
>> -	unsigned char uc, symToByte[256], mtfSymbol[256], *selectors;
>> +		i, j, k, t, runPos, symCount, symTotal, nSelectors;
>> +	static int byteCount[256];
>> +	unsigned char uc, *selectors;
>> +	static unsigned char symToByte[256], mtfSymbol[256];
>>   	unsigned int *dbuf, origPtr;
>>      
> Um...  Some details might be useful, starting with "why can't that function
> be called from several processes at once"...
>    

Al, to be honest, I'm not 100% if this is single-threaded or not :/.  I 
was hoping that by throwing the patch out I would get either an ACK or a 
NAK on it because of the single threaded issue.  It seems to me (and I 
admit I might be totally wrong) that the bunzip2 function is only called 
during early boot,

#ifdef PREBOOT
STATIC int INIT decompress(unsigned char *buf, int len,
                         int(*fill)(void*, unsigned int),
                         int(*flush)(void*, unsigned int),
                         unsigned char *outbuf,
                         int *pos,
                         void(*error_fn)(char *x))
{
         return bunzip2(buf, len - 4, fill, flush, outbuf, pos, error_fn);
}
#endif

... which (again, if the assumptions I'm making are correct) means that 
only one cpu will be active.

/me hopes someone will correct him if he's wrong and that's why hpa and 
phillip are cc'd directly

If it isn't single threaded, then you're right -- a PREBOOT malloc is 
the way to go.

P.
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