> -----Original Message-----
> From: Thomas Monjalon [mailto:tho...@monjalon.net]
> Sent: Wednesday, July 4, 2018 6:14 AM
> To: Zhang, Qi Z <qi.z.zh...@intel.com>
> Cc: dev@dpdk.org; Burakov, Anatoly <anatoly.bura...@intel.com>; Ananyev,
> Konstantin <konstantin.anan...@intel.com>; Richardson, Bruce
> <bruce.richard...@intel.com>; Yigit, Ferruh <ferruh.yi...@intel.com>; Shelton,
> Benjamin H <benjamin.h.shel...@intel.com>; Vangati, Narender
> <narender.vang...@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v8 04/19] ethdev: introduce device lock
>
> 03/07/2018 17:08, Zhang, Qi Z:
> > From: Thomas Monjalon [mailto:tho...@monjalon.net]
> > > 02/07/2018 07:44, Qi Zhang:
> > > > Introduce API rte_eth_dev_lock and rte_eth_dev_unlock to let
> > > > application lock or unlock on specific ethdev, a locked device
> > > > can't be detached, this help applicaiton to prevent unexpected
> > > > device detaching, especially in multi-process envrionment.
> > >
> > > Trying to understand: a process of an application could try to
> > > detach a port while another process is against this decision.
> > > Why an application needs to be protected against itself?
> >
> > I think we can regard this as a help function, it help application to
> > simplified
> the situation when one process want to detach a device while another one is
> still using it.
> > Application can register a callback which can do to necessary clean up (like
> stop traffic, release memory ...) before device be detached.
>
> Yes I agree such hook can be a good idea.
>
>
> > > I guess it is only an application inter-process management.
> > > If we really want to provide such helper in DPDK, it should not be
> > > limited to ethdev.
> >
> > Once we move to eal layer, we will have rte_eal_dev_lock/unlock(devname,
> busname).
> > But its also better we keep rte_eth_dev_lock/unlock to make ethdev API
> > more completed (any port be locked means underline rte_device also be
> locked?) and this is same for other device family.
>
> No. Again, a port is not exactly a device.
> There can be several ports per device.
Yes, I know that.
what I mean is, we should assume lock any port of that rte_device will prevent
the device be detached.
>
> I think the right place for this hook is in port-level API (ethdev, crypto,
> etc). And
> as we improve only ethdev currently, without any common genericity for other
> device classes, it is probably fine in ethdev for now.
> >
> > > (for info, see class implementation:
> > > https://patches.dpdk.org/patch/41605/)
> > >
> > > What about hardware unplug?
> > > Can we detach the locked ports associated to the unplugged device?
> >
> > NO, we can't.
> > But do you think, we need to introduce a "force detach" version, which will
> ignore all locks.
>
> No, I don't think so.
> I am just trying to show that you cannot really "lock" a port.
> Maybe you should just rename those functions.
> After all, it is just a pre-detach hook.
> Wait, how is it different of RTE_ETH_EVENT_DESTROY callback?
> Perhaps we just need to improve the handling of the DESTROY event?
I have thought about this before.
Not like RTE_ETH_EVENT_DESTROY and other event hook, the hook here need to give
feedback, pass or fail will impact the following behavior, this make it
special, so I separate it from all exist rte_eth_event_type handle mechanism.
The alternative solution is
we just introduce a new event type like RTE_ETH_EVENT_PRE_DETACH and reuse all
exist API
rte_eth_dev_callback_register/rte_eth_dev_callback_unregister.
But in _rte_eth_dev_callback_process we need to add a code branch for
PRE_DETACH handle.
If (event = RTE_ETH_EVENT_PRE_DETACH)
<...>.
else {
<....>
}
And we may also need to keep rte_eth_dev_lock/unlock which will register a
default callback for PRE_DETACH.
What do you think about?
>
>
