Re: [PATCH] IB/core: Suppress a sparse warning

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 03/10/14 17:08, Paul E. McKenney wrote:
> On Mon, Mar 10, 2014 at 04:02:13PM +0100, Yann Droneaud wrote:
>> Hi,
>>
>> Le lundi 10 mars 2014 à 15:26 +0100, Bart Van Assche a écrit :
>>> On 03/10/14 14:33, Yann Droneaud wrote:
>>>> Le lundi 10 mars 2014 à 13:22 +0100, Bart Van Assche a écrit :
>>>>> Suppress the following sparse warning:
>>>>> include/rdma/ib_addr.h:187:24: warning: cast removes address space of expression
>>>>
>>>> You should explain why there's a warning here, and why is it safe to
>>>> cast. (I believe it's related to RCU domain ?)
>>>
>>> Hello Yann,
>>>
>>> Now that I've had a closer look at the code in include/rdma/ib_addr.h,
>>> that code probably isn't safe. How about the (untested) patch below ?
>>>
>>
>> Thanks for investigating.
>>
>> I'm not an expert in RCU, but I believe it then miss the RCU annotations
>> around the RCU reader section (ensure correct ordering if I recall
>> correctly).
>>
>> Cc: "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> 
> If the rcu_read_lock() isn't supplied by all callers to this function,
> then yes, it needs to be supplied as Yann shows below.
> 
> The CONFIG_PROVE_RCU=y Kconfig option can help determine that they are
> needed, but of course cannot prove that they are not needed, at least
> not unless you have a workload that exercises all possible calls to
> this function.

Hello Moni,

I think this warning got introduced via commit "IB/cma: IBoE (RoCE)
IP-based GID addressing" (7b85627b9f02f9b0fb2ef5f021807f4251135857;
December 12, 2013). Can you follow this up further ?

Thanks,

Bart.
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