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SubjectRe: [git patch review 1/4] IPoIB: Don't start send-only joins while multicast thread is stopped
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Date
 > Roland Dreier <rolandd@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
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