[dpdk-stable] patch 'service: fix identification of service running on other lcore' has been queued to stable release 19.11.3

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 19.11.3

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 05/21/20. 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.

Thanks.

Luca Boccassi

---
>From 99303c675dd25151ed360468a049c909531dad1e 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 4cf5254cc3..62618910f6 100644
--- a/lib/librte_eal/common/rte_service.c
+++ b/lib/librte_eal/common/rte_service.c
@@ -360,7 +360,7 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,
 /* Expects the service 's' is valid. */
 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)
 		return -EINVAL;
@@ -374,7 +374,7 @@ 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;
 
@@ -412,24 +412,14 @@ 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;
 }
@@ -449,7 +439,7 @@ rte_service_runner_func(void *arg)
 			if (!service_valid(i))
 				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);
 		}
 
 		cs->loops++;
-- 
2.20.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-05-19 14:04:51.136888089 +0100
+++ 0163-service-fix-identification-of-service-running-on-oth.patch	2020-05-19 14:04:44.504653593 +0100
@@ -1,15 +1,16 @@
-From 5c76111f068c4ef8aff4f5b4e2e641a21ff733a0 Mon Sep 17 00:00:00 2001
+From 99303c675dd25151ed360468a049c909531dad1e 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.
 
-Cc: stable at dpdk.org
 Fixes: 8d39d3e237c2 ("service: fix race in service on app lcore function")
 
 Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
@@ -20,7 +21,7 @@
  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 b8c465eb96..c283408cf1 100644
+index 4cf5254cc3..62618910f6 100644
 --- a/lib/librte_eal/common/rte_service.c
 +++ b/lib/librte_eal/common/rte_service.c
 @@ -360,7 +360,7 @@ rte_service_runner_do_callback(struct rte_service_spec_impl *s,