On 03/11/2015 04:23 PM, Ahmed S. Darwish wrote:
> From: Ahmed S. Darwish <ahmed.darw...@valeo.com>
>
> A number of tx queue wake-up events went missing due to the
> outlined scenario below. Start state is a pool of 16 tx URBs,
> active tx_urbs count = 15, with the netdev tx queue open.
>
> start_xmit() tx_acknowledge()
> ............ ................
> atomic_inc(&tx_urbs);
> if (atomic_read(&tx_urbs) >= 16) {
> URB completion IRQ!
> -->
> atomic_dec(&tx_urbs);
> netif_wake_queue();
> return;
> <--
> end of IRQ!
> netif_stop_queue();
> }
>
> At the end, the correct state expected is a 15 tx_urbs count
> value with the tx queue state _open_. Due to the race, we get
> the same tx_urbs value but with the tx queue state _stopped_.
> The wake-up event is completely lost.
>
> Thus avoid hand-rolled concurrency mechanisms and use a proper
> lock for contexts protection.I'm missing a spin_lock_init(), right? Please compile and test your code with everything switch on in Kernel hacking -> Lock Debugging. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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