Re: Bug in kernel code?

["Stephen C. Biggs" <s.biggs@softier.com>]

On 27 Aug 2002 at 17:23, David S. Miller wrote:

>    From: "Stephen C. Biggs" <s.biggs@softier.com>
>    Date: Tue, 27 Aug 2002 17:24:19 -0700
> 
>    ........... Notice the --order >=0 in the do while test... since order is declared as an unsigned 
>    long, this test is a pointless comparison and never fails, causing an infinite loop if the 
>    hashtable is empty.  
>    
>    My fix to this is to change the test to have
>    while (dentry_hashtable == NULL && order-- != 0);
>    
>    Could someone check me on this?
>    
> Your analysis is right but the fix is wrong, we do want to
> try order == 0 on very small memory systems, and you should
> not decrement the order at the beginning of the loop.  We
> want to use the "order" calculated.
> 
> Just make 'order' signed long to fix this bug.
> 

NO!  That won't work either.  This is a "do while" loop so the first test is always done and if 
order is 0, the check will be done AFTER the decrement, so this works.  Changing it to a signed 
long loses you a bit.