Re: [dpdk-dev] [PATCH 10/11] net/failsafe: fix sub-device ownership race

["Gaëtan Rivet" <gaetan.rivet@6wind.com>]

On Wed, May 09, 2018 at 03:43:31PM +0200, Thomas Monjalon wrote:
> 09/05/2018 15:30, Gaëtan Rivet:
> > On Wed, May 09, 2018 at 01:01:58PM +0000, Matan Azrad wrote:
> > > Regarding uint32
> > > The maximum port id number can be 0xffff.
> > > In this case the loop will be infinite if we use uint16 to iterate over all the ports.
> > 
> > If RTE_MAX_ETHPORTS is set to 0xffff, an array rte_eth_devices[0xffff]
> > would be defined statically, and I think other issues would arise
> > before our being stuck in an infinite loop?
> > 
> > In any case, if this had to be fixed, then there should be a
> > BUILD_BUG_ON RTE_MAX_ETHPORTS being 0xffff, in the relevant part of
> > librte_ethdev, instead of relying on librte_ethdev users skirting
> > shortfalls of the library. Anyone iterating on port IDs should expect the
> > port_id type to be sufficient to hold this information.
> 
> Interesting thought.
> I vote for keeping Matan's option as it is correct,
> and will accept a patch in 18.08 for your option (BUILD_BUG_ON).
> Maybe we should send a deprecation notice before limiting the max
> number of ports to 0xfffe? Or is it ridiculous for such unlikely constraint?
> 
> 

No actually the issue is when RTE_MAX_ETHPORTS is equal (or superior) to
0x10000.

If this is an issue that you think is worth having a workaround here,
you should also consider that rte_eth_find_next_owned_by (and
rte_eth_find_next, even if this one should be phased out), would also
result in an overflow and an infinite loop.

-- 
Gaëtan Rivet
6WIND