PERFORCE change 104029 for review

[Divacky Roman]

On Tue, Aug 15, 2006 at 11:27:54AM -0400, John Baldwin wrote:
> On Tuesday 15 August 2006 10:07, Roman Divacky wrote:
> > http://perforce.freebsd.org/chv.cgi?CH=104029
> > 
> > Change 104029 by rdivacky at rdivacky_witten on 2006/08/15 14:06:41
> > 
> > 	Protect against racing concurent creation in futex_get()
> > 	
> > 	Pointed out by: jhb
> > 
> > Affected files ...
> > 
> > .. //depot/projects/soc2006/rdivacky_linuxolator/compat/linux/linux_futex.c#24 
> edit
> > 
> > Differences ...
> > 
> > 
> ==== //depot/projects/soc2006/rdivacky_linuxolator/compat/linux/linux_futex.c#24 
> (text+ko) ====
> > 
> > @@ -342,13 +342,13 @@
> >  	if (locked == FUTEX_UNLOCKED)
> >     	   	FUTEX_UNLOCK;
> >  
> > +	if (locked == FUTEX_UNLOCKED)
> > +   	   	FUTEX_LOCK;
> 
> Looks like you should collapse the lock/unlock.  However, it's probably best 
> to use mutexes instead of sx locks, and to instead do something like this:
 
the lock here IS a mutex...
 
> 	lock();
> 	if (item in list) {
> 		item->ref++;
> 		unlock();
> 		return (item);
> 	}
> 	unlock();
> 
> 	new_item = new_item();
> 
> 	lock();
> 	if (item in list) {
> 		item->ref++;
> 		unlock();
> 		free(new_item);
> 		return (item);
> 	}
> 	insert new_item
> 	new_item->ref++;
> 	unlock();
> 	return (new_item)

isnt this exactly what I am doing in later revision?