Re: [PATCH 2/2] net: ethernet: stmmac: remove private tx queue lock

[Lino Sanfilippo]

Hi Pavel,

On 07.12.2016 22:37, Pavel Machek wrote:
> On Wed 2016-12-07 21:05:38, Lino Sanfilippo wrote:
>> The driver uses a private lock for synchronization between the xmit
>> function and the xmit completion handler, but since the NETIF_F_LLTX flag
>> is not set, the xmit function is also called with the xmit_lock held.
>> 
>> On the other hand the xmit completion handler first takes the private lock
>> and (in case that the tx queue has been stopped) the xmit_lock, leading to
>> a reverse locking order and the potential danger of a deadlock.
>> 
>> Fix this by removing the private lock completely and synchronizing the xmit
>> function and completion handler solely by means of the xmit_lock. By doing
>> this remove also the now unnecessary double check for a stopped tx queue.
>> 
> 
> FYI, here's modified version. I believe _bh versions are needed, and
> I'm testing that version now. (Oh and I also ported it to net-next).
> 
> It survived 30 minutes of testing so far...
> 

First off, thanks for testing.
Hmm. I dont understand why _bh would be needed. We call that function from
BH context only (napi poll and timer).
Any idea?

Lino