distributor: fix livelock on flush

[ upstream commit 96c3438 ]

The Distributor autotest can lock if ran enough times. Worker and
distributor threads get into a livelock situation waiting on each
other.

To repeat:
`while sudo sh -c "echo 'distributor_autotest' |
		./build/app/test/dpdk-test"; do :; done`

The root cause is where we are flushing on exit, and do not wait for
all worker packets to be returned before exiting.
Add a delay on flush so that all worker packets are returned before
completing the flush.

Bugzilla ID: 316
Fixes: 775003a ("distributor: add new burst-capable library")

Reported-by: Michael Santana <msantana@redhat.com>
Signed-off-by: David Hunt <david.hunt@intel.com>
Signed-off-by: Liang Ma <liang.j.ma@intel.com>
Tested-by: Michael Santana <msantana@redhat.com>

lib/librte_distributor/rte_distributor.c

@@ -541,6 +541,9 @@ rte_distributor_flush_v1705(struct rte_distributor *d)
 	while (total_outstanding(d) > 0)
 		rte_distributor_process(d, NULL, 0);
 
+	/* wait 10ms to allow all worker drain the pkts */
+	rte_delay_us(10000);
+
 	/*
 	 * Send empty burst to all workers to allow them to exit
 	 * gracefully, should they need to.