PERFORCE change 104043 for review
Divacky Roman
xdivac02 at stud.fit.vutbr.cz
Tue Aug 15 15:44:26 UTC 2006
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 at 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
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