Re: [dpdk-dev] [PATCH v2 4/4] net/mlx5: engage free on completion queue

[Slava Ovsiienko <viacheslavo@mellanox.com>]

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Thursday, January 9, 2020 17:19
> To: Slava Ovsiienko <viacheslavo@mellanox.com>; dev@dpdk.org
> Cc: Matan Azrad <matan@mellanox.com>; Raslan Darawsheh
> <rasland@mellanox.com>; Ori Kam <orika@mellanox.com>; Thomas
> Monjalon <thomas@monjalon.net>
> Subject: Re: [dpdk-dev] [PATCH v2 4/4] net/mlx5: engage free on completion
> queue
> 
> On 1/9/2020 10:56 AM, Viacheslav Ovsiienko wrote:
> > The free on completion queue keeps the indices of elts array, all mbuf
> > stored below this index should be freed on arrival of normal send
> > completion. In debug version it also contains an index of completed
> > transmitting descriptor (WQE) to check queues synchronization.
> >
> > Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> > Acked-by: Matan Azrad <matan@mellanox.com>
> 
> <...>
> 
> > @@ -2108,17 +2108,18 @@ enum mlx5_txcmp_code {
> >  			/*
> >  			 * We are going to fetch all entries with
> >  			 * MLX5_CQE_SYNDROME_WR_FLUSH_ERR status.
> > +			 * The send queue is supposed to be empty.
> >  			 */
> >  			++ci;
> > +			txq->cq_pi = ci;
> > +			last_cqe = NULL;
> >  			continue;
> >  		}
> >  		/* Normal transmit completion. */
> > +		assert(ci != txq->cq_pi);
> > +		assert((txq->fcqs[ci & txq->cqe_m] >> 16) == cqe-
> >wqe_counter);
> 
> And same comments on these as previous patches, we spend some effort to
> remove the 'rte_panic' from drivers, this is almost same thing.
> 
> I think a driver shouldn't decide to exit whole application, it's effect should be
> limited to the driver.
> 
> Assert is useful for debug and during development, but not sure having them
> in the production code.

IIRC, "assert" is standard C function. Compiled only if there is no NDEBUG defined.
So, assert does exactly what you are saying - provide the debug break
not allowing the bug to evolve. And no this break in production code.

With best regards, Slava