[dpdk-stable] patch 'service: fix identification of service running on other lcore' has been queued to LTS release 18.11.9

[Kevin Traynor]

Hi,

FYI, your patch has been queued to LTS release 18.11.9

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 06/10/20. 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-queue

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable-queue/commit/e41b1e38cc5bb71254248dcb3ea0e3242adefe58

Thanks.

Kevin.

---
>From e41b1e38cc5bb71254248dcb3ea0e3242adefe58 Mon Sep 17 00:00:00 2001
From: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
Date: Wed, 6 May 2020 23:28:00 +0800
Subject: [PATCH] service: fix identification of service running on other lcore

[ upstream commit 5c76111f068c4ef8aff4f5b4e2e641a21ff733a0 ]

The logic to identify if the MT unsafe service is running on another
core can return -EBUSY spuriously. In such cases, running the service
becomes costlier than using atomic operations. Assume that the
application passes the right parameters and reduce the number of
instructions for all cases.

Fixes: 8d39d3e237c2 ("service: fix race in service on app lcore function")

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
Reviewed-by: Phil Yang <phil.yang at arm.com>
Acked-by: Harry van Haaren <harry.van.haaren at intel.com>
---
 lib/librte_eal/common/rte_service.c | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c
index e71e1efaa8..0030e44e94 100644
--- a/lib/librte_eal/common/rte_service.c
+++ b/lib/librte_eal/common/rte_service.c
@@ -360,5 +360,5 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
 static int32_t
 service_run(uint32_t i, struct core_state *cs, uint64_t service_mask,
-	    struct rte_service_spec_impl *s)
+	    struct rte_service_spec_impl *s, uint32_t serialize_mt_unsafe)
 {
 	if (!s)
@@ -374,5 +374,5 @@ service_run(uint32_t i, struct core_state *cs, uint64_t service_mask,
 	cs->service_active_on_lcore[i] = 1;
 
-	if (service_mt_safe(s) == 0) {
+	if ((service_mt_safe(s) == 0) && (serialize_mt_unsafe == 1)) {
 		if (!rte_atomic32_cmpset((uint32_t *)&s->execute_lock, 0, 1))
 			return -EBUSY;
@@ -412,22 +412,12 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe)
 	SERVICE_VALID_GET_OR_ERR_RET(id, s, -EINVAL);
 
-	/* Atomically add this core to the mapped cores first, then examine if
-	 * we can run the service. This avoids a race condition between
-	 * checking the value, and atomically adding to the mapped count.
+	/* Increment num_mapped_cores to reflect that this core is
+	 * now mapped capable of running the service.
 	 */
-	if (serialize_mt_unsafe)
-		rte_atomic32_inc(&s->num_mapped_cores);
+	rte_atomic32_inc(&s->num_mapped_cores);
 
-	if (service_mt_safe(s) == 0 &&
-			rte_atomic32_read(&s->num_mapped_cores) > 1) {
-		if (serialize_mt_unsafe)
-			rte_atomic32_dec(&s->num_mapped_cores);
-		return -EBUSY;
-	}
+	int ret = service_run(id, cs, UINT64_MAX, s, serialize_mt_unsafe);
 
-	int ret = service_run(id, cs, UINT64_MAX, s);
-
-	if (serialize_mt_unsafe)
-		rte_atomic32_dec(&s->num_mapped_cores);
+	rte_atomic32_dec(&s->num_mapped_cores);
 
 	return ret;
@@ -449,5 +439,5 @@ rte_service_runner_func(void *arg)
 				continue;
 			/* return value ignored as no change to code flow */
-			service_run(i, cs, service_mask, service_get(i));
+			service_run(i, cs, service_mask, service_get(i), 1);
 		}
 
-- 
2.21.3

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-06-05 19:20:52.015288547 +0100
+++ 0020-service-fix-identification-of-service-running-on-oth.patch	2020-06-05 19:20:50.741042381 +0100
@@ -1 +1 @@
-From 5c76111f068c4ef8aff4f5b4e2e641a21ff733a0 Mon Sep 17 00:00:00 2001
+From e41b1e38cc5bb71254248dcb3ea0e3242adefe58 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 5c76111f068c4ef8aff4f5b4e2e641a21ff733a0 ]
+
@@ -12 +13,0 @@
-Cc: stable at dpdk.org
@@ -23 +24 @@
-index b8c465eb96..c283408cf1 100644
+index e71e1efaa8..0030e44e94 100644
@@ -26 +27 @@
-@@ -361,5 +361,5 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
+@@ -360,5 +360,5 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
@@ -33 +34 @@
-@@ -375,5 +375,5 @@ service_run(uint32_t i, struct core_state *cs, uint64_t service_mask,
+@@ -374,5 +374,5 @@ service_run(uint32_t i, struct core_state *cs, uint64_t service_mask,
@@ -40 +41 @@
-@@ -413,22 +413,12 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe)
+@@ -412,22 +412,12 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t serialize_mt_unsafe)
@@ -68 +69 @@
-@@ -450,5 +440,5 @@ rte_service_runner_func(void *arg)
+@@ -449,5 +439,5 @@ rte_service_runner_func(void *arg)