[dpdk-dev] [PATCH v3 6/9] eal: register non-EAL threads as lcores

[Bruce Richardson]

On Tue, Jun 23, 2020 at 09:49:18AM +0200, David Marchand wrote:
> Hello Konstantin,
> 
> On Mon, Jun 22, 2020 at 5:49 PM Ananyev, Konstantin
> <konstantin.ananyev at intel.com> wrote:
> > > diff --git a/lib/librte_eal/common/eal_common_lcore.c b/lib/librte_eal/common/eal_common_lcore.c
> > > index 86d32a3dd7..7db05428e7 100644
> > > --- a/lib/librte_eal/common/eal_common_lcore.c
> > > +++ b/lib/librte_eal/common/eal_common_lcore.c
> > > @@ -220,3 +221,38 @@ rte_socket_id_by_idx(unsigned int idx)
> > >       }
> > >       return config->numa_nodes[idx];
> > >  }
> > > +
> > > +static rte_spinlock_t lcore_lock = RTE_SPINLOCK_INITIALIZER;
> > > +
> > > +unsigned int
> > > +eal_lcore_non_eal_allocate(void)
> > > +{
> > > +     struct rte_config *cfg = rte_eal_get_configuration();
> > > +     unsigned int lcore_id;
> > > +
> > > +     rte_spinlock_lock(&lcore_lock);
> >
> > I think it will break current DPDK MP modes.
> > The problem here - rte_config (and lcore_role[]) is in shared memory,
> > while the lock is local.
> > Simplest way probably to move lcore_lock to rte_config.
> 
> Even before this series, MP has no protection on lcore placing between
> primary and secondary processes.
> Personally, I have no use for DPDK MP and marking MP as not supporting
> this new feature is tempting for a first phase.
> If this is a strong requirement, I can look at it in a second phase.
> What do you think?
> 
I think that is reasonable for a new feature. I suspect those wanting to
dynamically manage their own threads probably do not care about
multi-process mode. 

However, this limitation probably needs to be clearly called out in the
docs.

/Bruce