> On Oct 29, 2018, at 7:18 AM, Thomas Monjalon <tho...@monjalon.net> wrote: > > 29/10/2018 14:40, Alejandro Lucero: >> 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] >>> 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. > > Please, do not forget my other request to better comment functions.
Alejandro, This patchset has been merged to stable/17.11 per your request for the last release. You must send a fix to stable/17.11 as well, if you think there's a same issue there. Thanks, Yongseok >> 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. > > Yes, this is what concerns me. > You can add a comment explaining the unsafe which is not handled. > > >>>> 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 >>> >>> >> > > > > >
