From: Yongseok Koh <yskoh@mellanox.com>
To: Alejandro Lucero <alejandro.lucero@netronome.com>
Cc: "lei.a.yao@intel.com" <lei.a.yao@intel.com>,
Thomas Monjalon <thomas@monjalon.net>, dev <dev@dpdk.org>,
"Xu, Qian Q" <qian.q.xu@intel.com>,
"xueqin.lin@intel.com" <xueqin.lin@intel.com>,
"Burakov, Anatoly" <anatoly.burakov@intel.com>,
Ferruh Yigit <ferruh.yigit@intel.com>
Subject: Re: [dpdk-dev] [PATCH v3 0/6] use IOVAs check based on DMA mask
Date: Mon, 29 Oct 2018 18:54:34 +0000 [thread overview]
Message-ID: <621BE501-6B10-4053-AC33-50ABE0231A44@mellanox.com> (raw)
In-Reply-To: <3483377.PMXnpSGLS9@xps>
> On Oct 29, 2018, at 7:18 AM, Thomas Monjalon <thomas@monjalon.net> wrote:
>
> 29/10/2018 14:40, Alejandro Lucero:
>> On Mon, Oct 29, 2018 at 1:18 PM Yao, Lei A <lei.a.yao@intel.com> wrote:
>>> *From:* Alejandro Lucero [mailto:alejandro.lucero@netronome.com]
>>> On Mon, Oct 29, 2018 at 11:46 AM Thomas Monjalon <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.
>>
>> 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
>>>
>>>
>>
>
>
>
>
>
next prev parent reply other threads:[~2018-10-29 18:54 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-05 12:45 Alejandro Lucero
2018-10-05 12:45 ` [dpdk-dev] [PATCH v3 1/6] mem: add function for checking memsegs IOVAs addresses Alejandro Lucero
2018-10-10 8:56 ` Tu, Lijuan
2018-10-11 9:26 ` Alejandro Lucero
2018-10-28 21:03 ` Thomas Monjalon
2018-10-05 12:45 ` [dpdk-dev] [PATCH v3 2/6] mem: use address hint for mapping hugepages Alejandro Lucero
2018-10-29 16:08 ` Dariusz Stojaczyk
2018-10-29 16:40 ` Alejandro Lucero
2018-10-05 12:45 ` [dpdk-dev] [PATCH v3 3/6] bus/pci: check iommu addressing limitation just once Alejandro Lucero
2018-10-05 12:45 ` [dpdk-dev] [PATCH v3 4/6] bus/pci: use IOVAs dmak mask check when setting IOVA mode Alejandro Lucero
2018-10-05 12:45 ` [dpdk-dev] [PATCH v3 5/6] net/nfp: check hugepages IOVAs based on DMA mask Alejandro Lucero
2018-10-05 12:45 ` [dpdk-dev] [PATCH v3 6/6] net/nfp: support IOVA VA mode Alejandro Lucero
2018-10-28 21:04 ` [dpdk-dev] [PATCH v3 0/6] use IOVAs check based on DMA mask Thomas Monjalon
2018-10-29 8:23 ` Yao, Lei A
2018-10-29 8:42 ` Thomas Monjalon
2018-10-29 9:07 ` Thomas Monjalon
2018-10-29 9:25 ` Alejandro Lucero
2018-10-29 9:44 ` Yao, Lei A
2018-10-29 9:36 ` Yao, Lei A
2018-10-29 9:48 ` Thomas Monjalon
2018-10-29 10:11 ` Alejandro Lucero
2018-10-29 10:15 ` Alejandro Lucero
2018-10-29 11:39 ` Alejandro Lucero
2018-10-29 11:46 ` Thomas Monjalon
2018-10-29 12:55 ` Alejandro Lucero
2018-10-29 13:18 ` Yao, Lei A
2018-10-29 13:40 ` Alejandro Lucero
2018-10-29 14:18 ` Thomas Monjalon
2018-10-29 14:35 ` Alejandro Lucero
2018-10-29 18:54 ` Yongseok Koh [this message]
2018-10-29 19:37 ` Alejandro Lucero
2018-10-30 10:10 ` Burakov, Anatoly
2018-10-30 10:11 ` Burakov, Anatoly
2018-10-30 10:19 ` Alejandro Lucero
2018-10-30 3:20 ` Lin, Xueqin
2018-10-30 9:41 ` Alejandro Lucero
2018-10-30 10:33 ` Lin, Xueqin
2018-10-30 10:38 ` Alejandro Lucero
2018-10-30 12:21 ` Lin, Xueqin
2018-10-30 12:37 ` Alejandro Lucero
2018-10-30 14:04 ` Alejandro Lucero
2018-10-30 14:14 ` Burakov, Anatoly
2018-10-30 14:45 ` Alejandro Lucero
2018-10-30 14:45 ` Lin, Xueqin
2018-10-30 14:57 ` Alejandro Lucero
2018-10-30 15:09 ` Lin, Xueqin
2018-10-30 10:18 ` Burakov, Anatoly
2018-10-30 10:23 ` Alejandro Lucero
-- strict thread matches above, loose matches on Subject: below --
2018-07-04 12:53 Alejandro Lucero
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