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

["Yao, Lei A" <lei.a.yao@intel.com>]

From: Alejandro Lucero [mailto:alejandro.lucero@netronome.com]
Sent: Monday, October 29, 2018 8:56 PM
To: Thomas Monjalon <thomas@monjalon.net>
Cc: Yao, Lei A <lei.a.yao@intel.com>; dev <dev@dpdk.org>; Xu, Qian Q <qian.q.xu@intel.com>; Lin, Xueqin <xueqin.lin@intel.com>; Burakov, Anatoly <anatoly.burakov@intel.com>; Yigit, Ferruh <ferruh.yigit@intel.com>
Subject: Re: [dpdk-dev] [PATCH v3 0/6] use IOVAs check based on DMA mask


On Mon, Oct 29, 2018 at 11:46 AM Thomas Monjalon <thomas@monjalon.net<mailto:thomas@monjalon.net>> wrote:
29/10/2018 12:39, Alejandro Lucero:
> 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.

The deadlock is a bigger concern I think.

I think once the call to rte_eal_check_dma_mask uses the maskbits instead of the mask, calling rte_memseg_walk_thread_unsafe avoids the deadlock.

Yao, can you try with the attached patch?

Hi, Lucero

This patch can fix the issue at my side. Thanks a lot
for you quick action.

BRs
Lei

> 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:
>
> -       if (rte_memseg_walk(check_iova, &mask))
> +       if (!rte_memseg_walk(check_iova, &mask))
>
> 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.

Anyway, the coding style requires to save the return value in a variable,
instead of nesting the call in an "if" condition.
And the "if" check should be explicitly != 0 because it is not a real boolean.

PS: please do not top post and avoid HTML emails, thanks