Date:   Fri, 12 Apr 2019 17:35:10 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Lorenzo Bianconi <lorenzo@kernel.org>, nbd@nbd.name,
        linux-wireless@vger.kernel.org
Subject: Re: [PATCH] mt76: usb: fix possible memory leak during suspend/resume
Message-ID: <20190412153509.GB3156@localhost.localdomain>
References: <cover.1555071870.git.lorenzo@kernel.org>
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 <20190412145442.GA2539@redhat.com>
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> On Fri, Apr 12, 2019 at 02:27:16PM +0200, Lorenzo Bianconi wrote:
> > Disable mt76u_tx_tasklet at the end of mt76u_stop_queues in order to
> > properly deallocate all pending skbs during suspend/resume phase
>=20
> On suspend/resume tx skb's are processed after tasklet_enable()
> in resume callback. There is issue with device removal though
> (during suspend or otherwise).

Hi Stanislaw,

I guess the right moment to deallocate the skbs is during suspend since res=
ume
can happen in very far future

>=20
> > Fixes: b40b15e1521f ("mt76: add usb support to mt76 layer")
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > ---
> >  drivers/net/wireless/mediatek/mt76/usb.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >=20
> > diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wir=
eless/mediatek/mt76/usb.c
> > index a3acc070063a..575207133775 100644
> > --- a/drivers/net/wireless/mediatek/mt76/usb.c
> > +++ b/drivers/net/wireless/mediatek/mt76/usb.c
> > @@ -842,10 +842,10 @@ static void mt76u_stop_tx(struct mt76_dev *dev)
> >  void mt76u_stop_queues(struct mt76_dev *dev)
> >  {
> >  	tasklet_disable(&dev->usb.rx_tasklet);
> > -	tasklet_disable(&dev->usb.tx_tasklet);
> > -
> >  	mt76u_stop_rx(dev);
> > +
> >  	mt76u_stop_tx(dev);
> > +	tasklet_disable(&dev->usb.tx_tasklet);
>=20
> If tasklet is scheduled and we disable it and never enable, we end up
> with infinite loop in tasklet_action_common(). This patch make the
> problem less reproducible since tasklet_disable() is moved after
> usb_kill_urb() -> tasklet_schedule(), but it is still possible.

I can see the point here. Maybe we can just run tasklet_kill instead of
tasklet_disable here (at least for tx one)

Regards,
Lorenzo

>=20
> I comprehansive have fix for that, but giving it more testing.
> Please drop this patch.
>=20
> Stanislaw

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