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

[Moni Shoua <monis-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 3/12/2014 12:15 PM, Bart Van Assche wrote:
> 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.
Sure. I'll look into it.
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