On Mon, Oct 29, 2018 at 1:18 PM Yao, Lei A <lei.a....@intel.com> wrote:
> > > > > *From:* Alejandro Lucero [mailto:alejandro.luc...@netronome.com] > *Sent:* Monday, October 29, 2018 8:56 PM > *To:* Thomas Monjalon <tho...@monjalon.net> > *Cc:* Yao, Lei A <lei.a....@intel.com>; dev <dev@dpdk.org>; Xu, Qian Q < > qian.q...@intel.com>; Lin, Xueqin <xueqin....@intel.com>; Burakov, > Anatoly <anatoly.bura...@intel.com>; Yigit, Ferruh <ferruh.yi...@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 <tho...@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. > > > Great! I will send an official patch with the changes. I have to say that I tested the patchset, but I think it was where legacy_mem was still there and therefore dynamic memory allocation code not used during memory initialization. There is something that concerns me though. Using rte_memseg_walk_thread_unsafe could be a problem under some situations although those situations being unlikely. Usually, calling rte_eal_check_dma_mask happens during initialization. Then it is safe to use the unsafe function for walking memsegs, but with device hotplug and dynamic memory allocation, there exists a potential race condition when the primary process is allocating more memory and concurrently a device is hotplugged and a secondary process does the device initialization. By now, this is just a problem with the NFP, and the potential race condition window really unlikely, but I will work on this asap. > 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 > >
