[dpdk-dev] [PATCH v8 01/17] distributor: fix missing handshake synchronization

[Honnappa Nagarahalli]

<snip>
> 
> rte_distributor_return_pkt function which is run on worker cores must wait
> for distributor core to clear handshake on retptr64 before using those
> buffers. While the handshake is set distributor core controls buffers and any
> operations on worker side might overwrite buffers which are unread yet.
> Same situation appears in the legacy single distributor. Function
> rte_distributor_return_pkt_single shouldn't modify the bufptr64 until
> handshake on it is cleared by distributor lcore.
> 
> Fixes: 775003ad2f96 ("distributor: add new burst-capable library")
> Cc: david.hunt at intel.com
> Cc: stable at dpdk.org
> 
> Signed-off-by: Lukasz Wojciechowski <l.wojciechow at partner.samsung.com>
> Acked-by: David Hunt <david.hunt at intel.com>
Looks good.
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>

> ---
>  lib/librte_distributor/rte_distributor.c        | 12 ++++++++++++
>  lib/librte_distributor/rte_distributor_single.c |  4 ++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/lib/librte_distributor/rte_distributor.c
> b/lib/librte_distributor/rte_distributor.c
> index 1c047f065..c6b19a388 100644
> --- a/lib/librte_distributor/rte_distributor.c
> +++ b/lib/librte_distributor/rte_distributor.c
> @@ -169,6 +169,18 @@ rte_distributor_return_pkt(struct rte_distributor *d,
>  			return -EINVAL;
>  	}
> 
> +	/* Spin while handshake bits are set (scheduler clears it).
> +	 * Sync with worker on GET_BUF flag.
> +	 */
> +	while (unlikely(__atomic_load_n(&(buf->retptr64[0]),
> __ATOMIC_RELAXED)
> +			& RTE_DISTRIB_GET_BUF)) {
> +		rte_pause();
> +		uint64_t t = rte_rdtsc()+100;
> +
> +		while (rte_rdtsc() < t)
> +			rte_pause();
> +	}
> +
>  	/* Sync with distributor to acquire retptrs */
>  	__atomic_thread_fence(__ATOMIC_ACQUIRE);
>  	for (i = 0; i < RTE_DIST_BURST_SIZE; i++) diff --git
> a/lib/librte_distributor/rte_distributor_single.c
> b/lib/librte_distributor/rte_distributor_single.c
> index abaf7730c..f4725b1d0 100644
> --- a/lib/librte_distributor/rte_distributor_single.c
> +++ b/lib/librte_distributor/rte_distributor_single.c
> @@ -74,6 +74,10 @@ rte_distributor_return_pkt_single(struct
> rte_distributor_single *d,
>  	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
>  	uint64_t req = (((int64_t)(uintptr_t)oldpkt) <<
> RTE_DISTRIB_FLAG_BITS)
>  			| RTE_DISTRIB_RETURN_BUF;
> +	while (unlikely(__atomic_load_n(&buf->bufptr64,
> __ATOMIC_RELAXED)
> +			& RTE_DISTRIB_FLAGS_MASK))
> +		rte_pause();
> +
>  	/* Sync with distributor on RETURN_BUF flag. */
>  	__atomic_store_n(&(buf->bufptr64), req, __ATOMIC_RELEASE);
>  	return 0;
> --
> 2.17.1