Re: [PATCH 4/4] [RFC] ipv6: Fix for possible ipv6 seqlock deadlock

[John Stultz]

On 09/26/2013 12:30 PM, Eric Dumazet wrote:
> On Thu, 2013-09-26 at 11:34 -0700, John Stultz wrote:
>> While enabling lockdep on seqlocks, I ran accross the warning below
>> caused by the ipv6 stats being updated in both irq and non-irq context.
>>
>> This is a novice attempt to correct the issue, and with this patch
>> the warning goes away. Any better solutions would be appreciated!
> ...
>
>>  
>>  out_err_release:
>> -	if (err == -ENETUNREACH)
>> +	if (err == -ENETUNREACH) {
>> +		unsigned long flags;
>> +		/* some of the stats are locked in irq context */
>> +		local_irq_save(flags);
>>  		IP6_INC_STATS_BH(net, NULL, IPSTATS_MIB_OUTNOROUTES);
>> +		local_irq_restore(flags);
>> +	}
>>  	dst_release(*dst);
>>  	*dst = NULL;
>>  	return err;
> You better change IP6_INC_STATS_BH() to IP6_INC_STATS()
>
> On x86 for example, no extra code will be generated (no need to disable
> hard or soft irqs)

Ah, thanks! Verified it resolves the warning as well, so I've changed my
patch to use your suggestion.

thanks again
-john
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