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

[Ananyev, Konstantin]

> -----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;
}

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