Re: [PATCH] 2.5.6-pre3 Fix small race in BSD accounting [part 2]

[Bob Miller <rem@osdl.org>]

On Mon, Mar 11, 2002 at 03:30:03PM -0500, Robert Love wrote:
> On Mon, 2002-03-11 at 15:07, Bob Miller wrote:
> 
> > While looking at the bug fix for part 1 I coded up this patch
> > to change the BSD accounting code to use a spinlock instead
> > of the BKL.
> 
> Oh, Good Job - BKL is evil.  And I think that is partly evident in the
> resulting code, and I have a couple comments about it.
> 
> I suspect the recursive nature of the BKL (and perhaps the locking rules
> such that you don't always hold alock, i.e. if name is not NULL) are
> responsible for:
> 
> 	if (!locked)
> 		spin_lock(&acct_lock);
> 
> which really isn't the prettiest or safest thing, although I don't
> actually see any problems with it here.  With the BKL removed, it may be
> better to rewrite the code in a cleaner and saner way.
> 
> I'd much rather see sane locking rules where we knew the callers and
> each function entry clearly either held or does not hold the spin_lock. 
> Make sure we don't call anything holding the lock, et cetera ...
> 
> Also, I like the struct but the defines are a bit ugly.  Why not just
> s/acct_lock/acct_globals.lock/, for example, in the code?  Or Just call
> the instance of the struct "acct" and have acct.lock, etc.
> 
> In other words, good job, but this is a development kernel - rip some of
> this cruft up and make it perfect, no?
> 
> 	Robert Love

Robert,

Thanks for the comments.  I was going for the minimal diff approach, but I
think the code would be better with a little re-arranging.  I'll make a
cut at it and re-submit.

-- 
Bob Miller					Email: rem@osdl.org
Open Source Development Lab			Phone: 503.626.2455 Ext. 17