ETHERNET WITH MULTIPLE LPWORK THREADS

```
Description: Recently, Ethernet drivers were modified to support multiple
work queue structures. The question was raised: "My only
reservation would be, how would this interact in the case of
having CONFIG_STM32_ETHMAC_LPWORK and CONFIG_SCHED_LPNTHREADS
> 1? Can it be guaranteed that one work item won't be
interrupted and execution switched to another? I think so but
am not 100% confident."

I suspect that you right. There are probably vulnerabilities
in the CONFIG_STM32_ETHMAC_LPWORK with CONFIG_SCHED_LPNTHREADS
> 1 case. But that really doesn't depend entirely upon the
change to add more work queue structures. Certainly with only
work queue structure you would have concurrent Ethernet
operations in that multiple LP threads; just because the work
structure is available, does not mean that there is not dequeued
work in progress. The multiple structures probably widens the
window for that concurrency, but does not create it.

The current Ethernet designs depend upon a single work queue to
serialize data. In the case of multiple LP threads, some
additional mechanism would have to be added to enforce that
serialization.

NOTE: Most drivers will call net_lock() and net_unlock() around
the critical portions of the driver work. In that case, all work
will be properly serialized. This issue only applies to drivers
that may perform operations that require protection outside of
the net_lock'ed region. Sometimes, this may require extending
the netlock() to be beginning of the driver work function.

Status: Open
Priority: High if you happen to be using Ethernet in this configuration.
```