From b77d3318d6a3ca266751031ff04520b7ad485529 Mon Sep 17 00:00:00 2001 From: Dmitry Kozlyuk Date: Mon, 11 Apr 2022 00:35:50 +0300 Subject: [PATCH] ethdev: prohibit polling stopped queue Whether it is allowed to call Rx/Tx functions for a stopped queue was undocumented. Some PMDs make this behavior a no-op either by explicitly checking the queue state or by the way how their routines are implemented or HW works. No-op behavior may be convenient for application developers. But it also means that pollers of stopped queues would go all the way down to PMD Rx/Tx routines, wasting cycles. Some PMDs would do a check for the queue state on data path, even though it may never be needed for a particular application. Also, use cases for stopping queues or starting them deferred do not logically require polling stopped queues. Use case 1: a secondary that was polling the queue has crashed, the primary is doing a recovery to free all mbufs. By definition the queue to be restarted is not polled. Use case 2: deferred queue start or queue reconfiguration. The polling thread must be synchronized anyway, because queue start and stop are non-atomic. Prohibit calling Rx/Tx functions on stopped queues. Fixes: 0748be2cf9a2 ("ethdev: queue start and stop") Cc: stable@dpdk.org Signed-off-by: Dmitry Kozlyuk Acked-by: Tyler Retzlaff --- lib/ethdev/rte_ethdev.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h index 04225bba4d..02df65d923 100644 --- a/lib/ethdev/rte_ethdev.h +++ b/lib/ethdev/rte_ethdev.h @@ -74,7 +74,7 @@ * rte_eth_rx_queue_setup()), it must call rte_eth_dev_stop() first to stop the * device and then do the reconfiguration before calling rte_eth_dev_start() * again. The transmit and receive functions should not be invoked when the - * device is stopped. + * device or the queue is stopped. * * Please note that some configuration is not stored between calls to * rte_eth_dev_stop()/rte_eth_dev_start(). The following configuration will