On Wed, 31 May 2017 13:26:43 +0300
Kalle Valo <kvalo@xxxxxxxxxxxxxx> wrote:
> Jia-Ju Bai <baijiaju1990@xxxxxxx> writes:
>
> > The driver may sleep under a spin lock, and the function call path is:
> > b43legacy_op_bss_info_changed (acquire the lock by spin_lock_irqsave)
> > b43legacy_synchronize_irq
> > synchronize_irq --> may sleep
> >
> > To fix it, the lock is released before b43legacy_synchronize_irq, and the
> > lock is acquired again after this function.
> >
> > Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxx>
> > ---
> > drivers/net/wireless/broadcom/b43legacy/main.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/wireless/broadcom/b43legacy/main.c b/drivers/net/wireless/broadcom/b43legacy/main.c
> > index f1e3dad..31ead21 100644
> > --- a/drivers/net/wireless/broadcom/b43legacy/main.c
> > +++ b/drivers/net/wireless/broadcom/b43legacy/main.c
> > @@ -2859,7 +2859,9 @@ static void b43legacy_op_bss_info_changed(struct ieee80211_hw *hw,
> > b43legacy_write32(dev, B43legacy_MMIO_GEN_IRQ_MASK, 0);
> >
> > if (changed & BSS_CHANGED_BSSID) {
> > + spin_unlock_irqrestore(&wl->irq_lock, flags);
> > b43legacy_synchronize_irq(dev);
> > + spin_lock_irqsave(&wl->irq_lock, flags);
>
> To me this looks like a fragile workaround and not a real fix. You can
> easily add new race conditions with releasing the lock like this.
>
I think releasing the lock possibly is fine. It certainly is better than
sleeping with a lock held.
We disabled the device interrupts just before this line.
However I think the synchronize_irq should be outside of the
conditional right after the write to B43legacy_MMIO_GEN_IRQ_MASK. (So
two lines above)
I don't think it makes sense to only synchronize if BSS_CHANGED_BSSID
is set.
On the other hand b43 does not have this irq-disabling foobar anymore.
So somebody must have removed it. Maybe you can find the commit that
removed this stuff from b43 and port it to b43legacy?
So I would vote for moving the synchronize_irq up outside of the
conditional and put the unlock/lock sequence around it.
And as a second patch on top of that try to remove this stuff
altogether like b43 did.
--
Michael
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