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Date: Tue, 15 Aug 2006 17:44:19 +0200
From: Divacky Roman <xdivac02@stud.fit.vutbr.cz>
To: John Baldwin <jhb@freebsd.org>
Message-ID: <20060815154418.GA60482@stud.fit.vutbr.cz>
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Cc: Roman Divacky <rdivacky@freebsd.org>,
	Perforce Change Reviews <perforce@freebsd.org>
Subject: Re: PERFORCE change 104043 for review
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On Tue, Aug 15, 2006 at 11:30:16AM -0400, John Baldwin wrote:
> On Tuesday 15 August 2006 11:23, Roman Divacky wrote:
> > http://perforce.freebsd.org/chv.cgi?CH=104043
> > 
> > Change 104043 by rdivacky@rdivacky_witten on 2006/08/15 15:22:57
> > 
> > 	Grrrr. Do the locking/unlocking correctly this time.
> > 
> > Affected files ...
> > 
> > .. //depot/projects/soc2006/rdivacky_linuxolator/compat/linux/linux_futex.c#27 
> edit
> > 
> > Differences ...
> > 
> > 
> ==== //depot/projects/soc2006/rdivacky_linuxolator/compat/linux/linux_futex.c#27 
> (text+ko) ====
> > 
> > @@ -339,9 +339,13 @@
> >  			return f;
> >  		}
> >  	}
> > +	if (locked == FUTEX_UNLOCKED)
> > +	   	FUTEX_UNLOCK;
> >  
> >  	/* Not found, create it */
> >  	f = malloc(sizeof(*f), M_LINUX, M_WAITOK);
> > +	if (locked == FUTEX_UNLOCKED)
> > +	   	FUTEX_LOCK;
> >  	f->f_uaddr = uaddr;
> >  	f->f_refcount = 1;
> >  	TAILQ_INIT(&f->f_waiting_proc);
> 
> This readds the race. :)  See my other e-mail on what you have to do to handle 
> it.

what is wrong with unprotected malloc? the memory at which f points at is nowhere referenced
nowhere added etc. until protected by the lock.

can you please explain me why is this wrong? I dont see any harm with two processes executing
this code paralelly.

thnx, roman