Re: [PATCH v3.14-rt] netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

* Paul E. McKenney | 2014-12-03 13:19:11 [-0800]:

>> Is that not actually a bug indepedent of RT ? 
>> without the rcu_read_lock/unlock who says that the 
>> rcu_dereference is still valid at this point ? 
>> I though that if bh are already disabled you still
>> need the read_lock. disabled bh would allow to "downgrad" 
>> the rcu_read_lock_bh to rcu_read_lock but you still need it.
>
>In vanilla kernels, anything that disables BH acts as rcu_read_lock_bh().
>So yes, you can have cases where rcu_read_lock_bh() is needed only in
>the -rt kernel.

But it won't hurt mainline using rcu_read_lock_bh() around
rcu_dereference_bh() right?
I am not going to apply this because that code is gone shortly after
v3.14 was released. The fm10k however does the same thing so atleast RCU
knows when to scream :)

>
>							Thanx, Paul

Sebastian