From: Elad Nachman <eladv6@gmail.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Eric Christian <erclists@gmail.com>, dev <dev@dpdk.org>,
Igor Ryzhov <iryzhov@nfware.com>
Subject: Re: [dpdk-dev] [PATCH v2] kni: Fix request overwritten
Date: Mon, 4 Oct 2021 17:58:45 +0300 [thread overview]
Message-ID: <CACXF7q=p_GSsQEbRwW+547vEsGT2j+8TyB=ViOuzOp6HNm7Ksw@mail.gmail.com> (raw)
In-Reply-To: <1a17d552-8b81-04f9-7594-61e84ea7990f@intel.com>
בתאריך יום ב׳, 4 באוק׳ 2021, 17:51, מאת Ferruh Yigit <
ferruh.yigit@intel.com>:
> On 10/4/2021 3:25 PM, Elad Nachman wrote:
>
> Can you please try to not top post, it will make impossible to follow this
> discussion later from the mail archives.
>
> > 1. Userspace will get an error
>
> So there is nothing special with returning '-EAGAIN', user will only
> observe an
> error.
> Wasn't initial intention to use '-EAGAIN' to try request again?
>
> To signal user-space to retry the operation.
>
> > 2. Waiting with rtnl locked causes a deadlock; waiting with rtnl unlocked
> > for interface down command causes a crash because of a race condition in
> > the device delete/unregister list in the kernel.
> >
>
> Why waiting with rthnl lock causes a deadlock? As said below we are already
> doing it, why it is different with retry logic?
>
> Because it can be interface down request.
> I agree to not wait with rtnl unlocked.
>
> > FYI,
> >
> > Elad.
> >
> > בתאריך יום ב׳, 4 באוק׳ 2021, 17:13, מאת Ferruh Yigit <
> > ferruh.yigit@intel.com>:
> >
> >> On 10/4/2021 2:09 PM, Elad Nachman wrote:
> >>> Hi,
> >>>
> >>> EAGAIN is propogated back to the kernel and to the caller.
> >>>
> >>
> >> So will the user get an error, or it will be handled by the kernel and
> >> retried?
> >>
> >>> We cannot retry from the kni kernel module since we hold the rtnl lock.
> >>>
> >>
> >> Why not? We are already waiting until a command time out, like
> >> 'kni_net_open()'
> >> can retry if 'kni_net_process_request()' returns '-EAGAIN'. And we can
> >> limit the
> >> number of retry for safety.
> >>
> >>> FYI,
> >>>
> >>> Elad
> >>>
> >>> בתאריך יום ב׳, 4 באוק׳ 2021, 16:05, מאת Ferruh Yigit <
> >>> ferruh.yigit@intel.com>:
> >>>
> >>>> On 9/24/2021 11:54 AM, Elad Nachman wrote:
> >>>>> Fix lack of multiple KNI requests handling support by introducing a
> >>>>> request in progress flag which will fail additional requests with
> >>>>> EAGAIN return code if the original request has not been processed
> >>>>> by user-space.
> >>>>>
> >>>>> Bugzilla ID: 809
> >>>>
> >>>> Hi Eric,
> >>>>
> >>>> Can you please test this patch, if it solves the issue you reported?
> >>>>
> >>>>>
> >>>>> Signed-off-by: Elad Nachman <eladv6@gmail.com>
> >>>>> ---
> >>>>> kernel/linux/kni/kni_net.c | 9 +++++++++
> >>>>> lib/kni/rte_kni.c | 2 ++
> >>>>> lib/kni/rte_kni_common.h | 1 +
> >>>>> 3 files changed, 12 insertions(+)
> >>>>>
> >>>>
> >>>> <...>
> >>>>
> >>>>> @@ -123,7 +124,15 @@ kni_net_process_request(struct net_device *dev,
> >>>> struct rte_kni_request *req)
> >>>>>
> >>>>> mutex_lock(&kni->sync_lock);
> >>>>>
> >>>>> + /* Check that existing request has been processed: */
> >>>>> + cur_req = (struct rte_kni_request *)kni->sync_kva;
> >>>>> + if (cur_req->req_in_progress) {
> >>>>> + ret = -EAGAIN;
> >>>>
> >>>> Overall logic in the KNI looks good to me, this helps to serialize the
> >>>> requests
> >>>> even for async ones.
> >>>>
> >>>> But can you please clarify how it behaves in the kernel side with
> >> '-EAGAIN'
> >>>> return type? Will linux call the ndo again, or will it just fail.
> >>>>
> >>>> If it just fails should we handle the re-try on '-EAGAIN' within the
> kni
> >>>> module?
> >>>>
> >>>>
> >>
> >>
>
> Elad.
next prev parent reply other threads:[~2021-10-04 14:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-24 10:54 Elad Nachman
2021-10-04 13:01 ` Ferruh Yigit
2021-10-04 13:09 ` Elad Nachman
2021-10-04 14:03 ` Ferruh Yigit
2021-10-04 14:25 ` Elad Nachman
2021-10-04 14:51 ` Ferruh Yigit
2021-10-04 14:58 ` Elad Nachman [this message]
2021-10-04 15:48 ` Ferruh Yigit
2021-10-04 16:18 ` Elad Nachman
2021-10-04 16:59 ` Eric Christian
2021-10-04 18:27 ` Elad Nachman
2021-10-08 20:23 ` Ferruh Yigit
2021-10-08 21:11 ` Ferruh Yigit
2021-10-04 14:14 ` Eric Christian
2021-10-04 14:56 ` Ferruh Yigit
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