[Linux-stm32] [PATCH net v3 1/5] net: stmmac: Fix incorrect location to set real_num_rx|tx_queues

[Jose Abreu]

From: Ong, Boon Leong <boon.leong.ong at intel.com>
Date: Jan/24/2020, 08:56:28 (UTC+00:00)

> >Why not use rtnl_is_locked() instead of the boolean ?
> 
> We know that stmmac_open() is called with rtnl_mutex locked by caller.
> And, stmmac_resume() is called without rtnl_mutex is locked by caller.
> If we replace the boolean with rtnl_is_locked(), then we will have the
> following logics in stmmac_hw_setup():-
> 
>      if (!rtnl_is_locked)   ---- (A)
>          rtnl_lock();
>      netif_set_real_num_rx_queues();
>      netif_set_real_num_tx_queues();
>      if (!rtnl_is_locked)   ---- (B)
>          rtnl_unlock();
> 
> For stmmac_open(), (A) is false but (B) is true. 
> So, the stmmac_open() exits with rtnl_mutex is released.
> Here, the above logic does not perserve the original rtnl_mutex
> is locked when stmmac_open() is called.
> 
> For stmmac_resume(), (A) is true, and (B) is also true.
> So, the stmmac_resume() exits with rtnl_mutex is released.
> Here, the above logic works well as the original rtnl_mutex is released
> when stmmac_resume() is called.
>  
> So, as far as I can see, the proposed boolean approach works fine for both
> stmmac_open() and stmmac_resume().
> 
> Do you agree? 

Can't you just wrap all the HW related logic in stmmac_resume() and 
stmmac_suspend() with the rtnl lock ? Seems like the right thing to do and 
you won't need the boolean.

---
Thanks,
Jose Miguel Abreu