[openib-general] Re: [git patch review 1/4] IPoIB: Don't start send-only joins while multicast thread is stopped

[Roland Dreier]

 > Roland Dreier <rolandd at cisco.com> wrote:
 > >
 > >  +	spin_lock_irq(&priv->lock);
 > >  +	set_bit(IPOIB_MCAST_STARTED, &priv->flags);
 > >  +	spin_unlock_irq(&priv->lock);
 > 
 > Strange to put a lock around an atomic op like that.
 > 
 > Sometimes it's valid.   If another cpu was doing:
 > 
 > 	spin_lock(lock);
 > 
 > 	if (test_bit(IPOIB_MCAST_STARTED))
 > 		something();
 > 	...
 > 	if (test_bit(IPOIB_MCAST_STARTED))
 > 		something_else();
 > 
 > 	spin_unlock(lock);
 > 
 > then the locked set_bit() makes sense.
 > 
 > But often it doesn't ;)

Good point.  Michael, any reason why the lock is there around the
set_bit()?  (And similarly for the corresponding clear_bit())

Thanks,
 Roland