Re: [dpdk-dev] [PATCH v3 0/6] use IOVAs check based on DMA mask

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 29-Oct-18 11:39 AM, Alejandro Lucero wrote:
> I got a patch that solves a bug when calling rte_eal_dma_mask using the 
> mask instead of the maskbits. However, this does not solves the deadlock.
> 
> Interestingly, the problem looks like a compiler one. Calling 
> rte_memseg_walk does not return when calling inside rt_eal_dma_mask, but 
> if you modify the call like this:
> 
> *diff --git a/lib/librte_eal/common/eal_common_memory.c 
> b/lib/librte_eal/common/eal_common_memory.c*
> 
> *index 12dcedf5c..69b26e464 100644*
> 
> *--- a/lib/librte_eal/common/eal_common_memory.c*
> 
> *+++ b/lib/librte_eal/common/eal_common_memory.c*
> 
> @@ -462,7 +462,7 @@rte_eal_check_dma_mask(uint8_t maskbits)
> 
> /* create dma mask */
> 
> mask = ~((1ULL << maskbits) - 1);
> 
> - if (rte_memseg_walk(check_iova, &mask))
> 
> +if (!rte_memseg_walk(check_iova, &mask))
> 
> /*
> 
> * Dma mask precludes hugepage usage.
> 
> * This device can not be used and we do not need to keep
> 
> 
> it works, although the value returned to the invoker changes, of course. 
> But the point here is it should be the same behaviour when calling 
> rte_memseg_walk than before and it is not.
> 
> 
> Anatoly, maybe you can see something I can not.
> 

memseg walk will return 0 only when each callback returned 0 and there 
were no more segments left to call callbacks on. If your code always 
returns 0, then return value of memseg_walk will always be zero.

If your code returns 1 or -1 in some cases, then this error condition 
will trigger. If it doesn't, then your condition by which you decide to 
return 1 or 0, is incorrect :) I couldn't spot any obvious issues there, 
but i'll recheck.

-- 
Thanks,
Anatoly