patch 'ethdev: prohibit polling stopped queue' has been queued to stable release 21.11.2

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 21.11.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 06/13/22. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable/commit/79dd4206a76ad622f3ea78700df40fbe6bd0d979

Thanks.

Kevin

---
>From 79dd4206a76ad622f3ea78700df40fbe6bd0d979 Mon Sep 17 00:00:00 2001
From: Dmitry Kozlyuk <dkozlyuk at nvidia.com>
Date: Mon, 11 Apr 2022 00:35:50 +0300
Subject: [PATCH] ethdev: prohibit polling stopped queue

[ upstream commit b77d3318d6a3ca266751031ff04520b7ad485529 ]

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")

Signed-off-by: Dmitry Kozlyuk <dkozlyuk at nvidia.com>
Acked-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
---
 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 1d11a002d5..0be04c5809 100644
--- a/lib/ethdev/rte_ethdev.h
+++ b/lib/ethdev/rte_ethdev.h
@@ -75,5 +75,5 @@
  * 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
-- 
2.34.3

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2022-06-09 12:34:30.476383256 +0100
+++ 0030-ethdev-prohibit-polling-stopped-queue.patch	2022-06-09 12:34:29.703980569 +0100
@@ -1 +1 @@
-From b77d3318d6a3ca266751031ff04520b7ad485529 Mon Sep 17 00:00:00 2001
+From 79dd4206a76ad622f3ea78700df40fbe6bd0d979 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit b77d3318d6a3ca266751031ff04520b7ad485529 ]
+
@@ -30 +31,0 @@
-Cc: stable at dpdk.org
@@ -39 +40 @@
-index 04225bba4d..02df65d923 100644
+index 1d11a002d5..0be04c5809 100644