RE: [PATCH] graph: fix head move when graph walk in mcore dispatch

["Wu, Jingjing" <jingjing.wu@intel.com>]

> -----Original Message-----
> From: Yan, Zhirun <zhirun.yan@intel.com>
> Sent: Wednesday, March 20, 2024 4:43 PM
> To: Wu, Jingjing <jingjing.wu@intel.com>; dev@dpdk.org
> Cc: jerinj@marvell.com; pbhagavatula@marvell.com; stable@dpdk.org
> Subject: RE: [PATCH] graph: fix head move when graph walk in mcore dispatch
> 
> 
> 
> > -----Original Message-----
> > From: Wu, Jingjing <jingjing.wu@intel.com>
> > Sent: Wednesday, March 20, 2024 2:25 PM
> > To: Yan, Zhirun <zhirun.yan@intel.com>; dev@dpdk.org
> > Cc: jerinj@marvell.com; pbhagavatula@marvell.com; stable@dpdk.org
> > Subject: RE: [PATCH] graph: fix head move when graph walk in mcore
> dispatch
> >
> >
> > > >  		/* skip the src nodes which not bind with current worker */
> > > >  		if ((int32_t)head < 0 && node->dispatch.lcore_id != graph-
> > > > >dispatch.lcore_id)
> > > >  			continue;
> > > > -
> > > > +		head++;
> > > If current src node not bind with current core, It will go into infinite loop.
> > > This line would have no chance to run.
> >
> > Seems reasonable, it might be OK to change "head<0" to "head <1" the
> condition
> > check?
> 
> No. "head<0" means it is src node.
> All src node would put before head = 0.  "Head<1" is confused.
> You could find the details of graph reel under rte_graph_walk_rtc() in
> lib/graph/rte_graph_model_rtc.h
> 
> I guess if there are some src node missed, it may be caused by wrong config,
> for example, the missed src node not pin to a lcore.
> Use rte_graph_model_mcore_dispatch_node_lcore_affinity_set() to pin the
> src node first.

I don't think it is confusing because head++ happens before head < 0 check.
Yes, it happens when lcore affinity is not set.
For example, we have two source nodes, both of them have no lcore affinity setting.
By current code, the second node will also be executed which is not as expected.

Thanks
Jingjing