[dpdk-stable] [PATCH] eal: fix querying DPDK version at runtime

[Bruce Richardson]

On Fri, Feb 05, 2021 at 09:05:43PM +0100, Thomas Monjalon wrote:
> 05/02/2021 20:39, Bruce Richardson:
> > For using a DPDK application, such as OVS, which is dynamically linked, the
> > DPDK version in use should always report the actual version, not the
> > version used at build time. This incorrect behaviour can be seen by
> > building OVS against one version of DPDK and running it against a later
> > one. Using "ovs-vsctl list Open_vSwitch" to query basic info, the
> > dpdk_version returned will be the build version not the currently running
> > one - which can be verified using the DPDK telemetry library client.
> > 
> >   $ sudo ovs-vsctl list Open_vSwitch | grep dpdk_version
> >   dpdk_version        : "DPDK 20.11.0-rc4"
> > 
> >   $ echo quit | sudo dpdk-telemetry.py
> >   Connecting to /var/run/dpdk/rte/dpdk_telemetry.v2
> >   {"version": "DPDK 21.02.0-rc2", "pid": 405659, "max_output_len": 16384}
> 
> Nice demonstration.
> 
> >  __rte_experimental
> >  int
> > -rte_telemetry_init(const char *runtime_dir, rte_cpuset_t *cpuset,
> > +rte_telemetry_init(const char *runtime_dir, const char *rte_version, rte_cpuset_t *cpuset,
> >  		const char **err_str);
> 
> It is changing the API.
> As it is experimental, you just need to mention it in the release notes.

I don't think I actually need to mention it there, because this API is more
"INTERNAL" than "EXPERIMENTAL". It's called automatically from
rte_eal_init(). I've done up patch http://patches.dpdk.org/patch/87806/
to correct this, including a RN addition. That should remove the need for a
doc update for this patch.

> 
> It is the fix. Do you think it should be merged quickly?
> Or wait for 21.05?
> 

I'm not sure either way to be honest. Given the bug has been around so
long, it's not exactly urgent. On the other hand, to get the fix the user
needs to rebuild their app, so having it sooner is nicer, and will mean it
would make the next LTS point release. Overall, though, I'm fine whichever
you decide.

/Bruce