Re: [PATCH] mt76: usb: fix possible memory leak during suspend/resume

[Stanislaw Gruszka <sgruszka@redhat.com>]

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

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).

> 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(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/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);

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 comprehansive have fix for that, but giving it more testing.
Please drop this patch.

Stanislaw