[dpdk-dev] [PATCH v3 7/7] app/testpmd: adjust ethdev port ownership

[Ananyev, Konstantin]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Ananyev, Konstantin
> Sent: Tuesday, January 23, 2018 3:12 PM
> To: Thomas Monjalon <thomas at monjalon.net>
> Cc: Matan Azrad <matan at mellanox.com>; Gaëtan Rivet <gaetan.rivet at 6wind.com>; Wu, Jingjing <jingjing.wu at intel.com>;
> dev at dpdk.org; Neil Horman <nhorman at tuxdriver.com>; Richardson, Bruce <bruce.richardson at intel.com>
> Subject: Re: [dpdk-dev] [PATCH v3 7/7] app/testpmd: adjust ethdev port ownership
> 
> 
> 
> > -----Original Message-----
> > From: Thomas Monjalon [mailto:thomas at monjalon.net]
> > Sent: Tuesday, January 23, 2018 2:19 PM
> > To: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> > Cc: Matan Azrad <matan at mellanox.com>; Gaëtan Rivet <gaetan.rivet at 6wind.com>; Wu, Jingjing <jingjing.wu at intel.com>;
> > dev at dpdk.org; Neil Horman <nhorman at tuxdriver.com>; Richardson, Bruce <bruce.richardson at intel.com>
> > Subject: Re: [PATCH v3 7/7] app/testpmd: adjust ethdev port ownership
> >
> > 23/01/2018 14:34, Ananyev, Konstantin:
> > > If that' s the use case, then I think you need to set device ownership at creation time -
> > > inside dev_allocate().
> > > Again that would avoid such racing conditions inside testpmd.
> >
> > The devices must be allocated at a low level layer.
> 
> No one arguing about that.
> But we can provide owner id information to the low level.
> 
> > When a new device appears (hotplug), an ethdev port should be allocated
> > automatically if it passes the whitelist/blacklist policy test.
> > Then we must decide who will manage this device.
> > I suggest notifying the DPDK libs first.
> > So a DPDK lib or PMD like failsafe can have the priority to take the
> > ownership in its notification callback.
> 
> Possible, but seems a bit overcomplicated.
> Why not just:
> 
> Have a global variable process_default_owner_id, that would be init once at startup.
> Have an LTS variable default_owner_id.
> It will be used by rte_eth_dev_allocate() caller can set dev->owner_id at creation time,
> so port allocation and setting ownership - will be an atomic operation.
> At the exit rte_eth_dev_allocate() will always reset default_owner_id=0:
> 
> rte_eth_dev_allocate(...)
> {
>    lock(owner_lock);
>    <allocate_port>
>    owner = RTE_PER_LCORE(default_owner_id);
>    if (owner == 0)
>        owner = process_default_owner_id;
>   set_owner(port, ..., owner);
>  unlock(owner_lock);
>  RTE_PER_LCORE(default_owner_id) = 0;

Or probably better to leave default_owner_id reset to the caller.
Another thing - we can use same LTS variable in all control ops to
allow/disallow changing of port configuration based on ownership.
Konstantin

> }
> 
> So callers who don't need any special ownership - don't need to do anything.
> Special callers (like failsafe) can set default_owenr_id just before calling hotplug
> handling routine.
> 
> Konstantin
> 
> 
>