linux-kernel - Re: RCU: how to suppress warnings from rcu_assign

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Message-Id: <20110730.201609.2157787571393748046.davem@davemloft.net>
Date:	Sat, 30 Jul 2011 20:16:09 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	shemminger@...tta.com, paulmck@...ux.vnet.ibm.com,
	mchan@...adcom.com, linux-kernel@...r.kernel.org
Subject: Re: RCU: how to suppress warnings from rcu_assign_pointer?

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 30 Jul 2011 14:17:05 +0200

> Le vendredi 29 juillet 2011 à 10:50 -0700, Stephen Hemminger a écrit :
>> Gcc now generates warnings from rcu_assign_pointer when passed the
>> address of something for example:
>> 	rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc);
>> This warning is harmless and should be surpressed but there maybe
>> other cases where we want that Gcc warning.
>> 
>> I tried various combinations of in rcu_assign_pointer macro
>>   #pragma GCC diagnostic push
>>   #pragma GCC diagnostic ignored "-Wlogical-op"
>>   ...
>>   #pragma GCC diagnostic pop
>> but macro's and pragma's don't nest with the correct scope for
>> this.
>> 
>> Maybe some one with more Gcc foo and time to waste could take
>> a crack at it.
> 
> I would just remove the test from rcu_assign_pointer().
> 
> We now have RCU_INIT_POINTER() for places we dont want/afford the
> smp_wmb()

Agreed:

Acked-by: David S. Miller <davem@...emloft.net>
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