Re: lock_kernel check...

["dan carpenter" <error27@email.com>]

----- Original Message -----
From: Dave Hansen <haveblue@us.ibm.com>
Date: Tue, 09 Jul 2002 10:41:01 -0700 
To: dan carpenter <error27@email.com>
Subject: Re: lock_kernel check...

> dan carpenter wrote:
>  > Smatch.pm is from the smatch.sf.net scripts page.  Smatch is a
>  > really unfinished code checker that I've been working on.  It is
>  > based on reading the papers about the Stanford checker.
> 
> There was a time when I was thinking about the same thing.  It kept 
> scaring me the more I thought about it.
> 

True.  But someone is going to write a checker at some point.  It's only a couple days work if you know what you are doing.  There doesn't seem to be much advantage in waiting a year or two.

>  > Unfortunately, after a night of sleep I realize that my script is
>  > broken for 2 reasons. 1)  Smatch.pm is meant to track state changes
>  > down different code paths.  But unfortunately it wasn't doing that
>  > in this case; it was just going down the code without taking into
>  > consideration any if_stmts  etc.  I'm extremely embarassed about
>  > that.  Sorry.
> 
> Don't be sorry.  The script is smarter than the people who caused the 
> errors.  (once again, probably me)
> 
>  > 2)  What the Stanford checker does is print an error
>  > if one return_stmt is called while the kernel is locked and one is
>  > called while the kernel is unlocked.  This seems reasonable.
> 
> Could you clarify that a bit?
> 

If someone made a mistake where they always returned under a kernel_lock() they would find the mistake themselves.  

Why would they return under kernel_lock() on error, for example, but not on success?  That would be confusing.  There would still be some false positives but the number of cases is really small.

regards,
dan carpenter


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