Re: [dpdk-dev] [PATCH v3 1/4] app/testpmd: allow detaching a port not closed

[Thomas Monjalon <thomas@monjalon.net>]

17/10/2018 12:30, Iremonger, Bernard:
> Hi Thomas,
> 
> From: Thomas Monjalon
> > 17/10/2018 08:26, Andrew Rybchenko:
> > > On 10/17/18 4:54 AM, Thomas Monjalon wrote:
> > > > The testpmd application aim is for testing; so order of operations
> > > > should not be enforced.
> > > >
> > > > There was a test to forbid detaching before closing a port.
> > > > However, it may interesting to test what happens in such case.
> > > > It is possible for a PMD to automatically close the port when detaching.
> > > >
> > > > Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> > >
> > > I'm afraid it could be a problem which the patch, since port close
> > > ensures that the port is not used for traffic forwarding.
> > > Right now the check is gone and we can detach port which is used for
> > > traffic forwarding on separate data cores.
> > > So, almost guaranteed crash.
> > 
> > Yes I can duplicate this check in detach_port().
> 
> I agree with Andrew that this will cause a crash.

As I answered, I will add a check that port is stopped.

> I don't understand why the sequence is changing here.
> The close(), detach()  sequence has been in place since the port hot plug work some years ago, user applications may already be using this sequence.

I explained the reason in the commit log:
Adding too much checks is wrong for a test application.
We must be free to call detach without close.