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

[Thomas Monjalon <thomas@monjalon.net>]

09/05/2018 16:03, Gaëtan Rivet:
> 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.

You get a point. I will remove the workaround uint32_t in v2,
so all the related issues can be fixed at once in a separate patch
using BUILD_BUG_ON.