[PATCH] ARM: Fix a race in the vfp_notifier() function on SMPsystems

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Fri, Dec 18, 2009 at 02:51:41PM +0000, Catalin Marinas wrote:
> On Fri, 2009-12-18 at 14:47 +0000, Russell King - ARM Linux wrote:
> > Actually, I think we should go further and kill off THREAD_NOTIFY_RELEASE
> > completely.  Added a few more people because EP93xx and PXA (well,
> > Xscale) is now impacted by this change.
> > 
> > [PATCH] ARM: Convert VFP/Crunch/XscaleCP thread_release() to exit_thread()
> > 
> > This avoids races in the VFP code where the dead thread may have
> > state on another CPU.  By moving this code to exit_thread(), we
> > will be running as the thread, and therefore be running on the
> > current CPU.
> > 
> > This means that we can ensure that the only local state is accessed
> > in the thread notifiers.
> > 
> > Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> [...]
> >  static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
> >  {
> > @@ -132,8 +135,8 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
> > 
> >         if (cmd == THREAD_NOTIFY_FLUSH)
> >                 vfp_thread_flush(thread);
> > -       else
> > -               vfp_thread_release(thread);
> > +       else if (cmd == THREAD_NOTIFY_EXIT)
> > +               vfp_thread_exit(thread);
> 
> Do we still need the second "if" or "else" will do (though it's safer if
> anyone adds some extra THREAD_NOTIFY_* in the future.

The previous patch iteration did need it, but this done doesn't.  Killed.