Aw: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.

[Lino Sanfilippo]

Hi,


> 
> 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?


Regards,
Lino

Aw: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.

[Lino Sanfilippo]

Hi,


> 
> 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?


Regards,
Lino