Re: [RFC] Re: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.

Hi,

On 07.12.2016 13:31, Pavel Machek wrote:

On Fri 2016-12-02 15:05:21, Lino Sanfilippo wrote:

quoted

Hi,

quoted

There's nothing that protect stmmac_poll() from running concurently
with stmmac_dma_interrupt(), right?

could it be that there is also another issue concerned locking?:
The tx completion handler takes the xmit_lock in case that the
netif_queue is stopped. This is AFAICS unnecessary, since both
xmit and completion handler are already synchronized by the private
tx lock. But it is IMHO also dangerous:

In the xmit handler we have the locking order
1. xmit_lock
2. private tx lock

while in the completion handler its the reverse:

1. private tx lock
2. xmit lock.

Do I miss something?

No, it seems you are right. Something like this?

Hmm. And can priv->tx_lock be removed, as we already rely on
netif_tx_lock?

David wanted indeed the private lock to be removed completely. See
this thread.

https://marc.info/?l=linux-netdev&m=148072001900620&w=2

If you can wait a bit, I already have patches prepared to fix this issue in both
drivers. I want to send them as soon as I am at home (a few hours).

Regards,
Lino