Re: [GIT PULL] MMC updates

[Nick Piggin]

Pierre Ossman wrote:
> Nick Piggin wrote:
>
> > > @@ -501,9 +501,9 @@ void mmc_detect_change(struct mmc_host *host,
> > > unsigned long delay)
> > > {
> > > #ifdef CONFIG_MMC_DEBUG
> > >     unsigned long flags;
> > > -    spin_lock_irqsave(host->lock, flags);
> > > +    spin_lock_irqsave(&host->lock, flags);
> > >     BUG_ON(host->removed);
> > > -    spin_unlock_irqrestore(host->lock, flags);
> > > +    spin_unlock_irqrestore(&host->lock, flags);
> > > #endif
> >
> > Do you actually need the lock there at all? What is it protecting?
>
>
> It makes sure we don't have any race when it comes to modifying
> host->removed.

If you want to ensure you always only modify host->removed from under
the spinlock, it would be enforcable by introducing an accessor function
and doing a BUG_ON(!spin_is_locked()) in there.

If you just want to ensure that host->removed is 0 at this point, you
shouldn't need any spinlocks AFAIKS... that way you can probably afford
to move it out from CONFIG_MMC_DEBUG and get wider testing.

--
SUSE Labs, Novell Inc.
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