[dpdk-stable] patch 'eventdev: fix race condition on timer list counter' has been queued to stable release 19.11.4

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 19.11.4

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 07/26/20. 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 b01bf3ceeeb3bfe4c1146cb58f92362f279f11f6 Mon Sep 17 00:00:00 2001
From: Phil Yang <phil.yang at arm.com>
Date: Tue, 7 Jul 2020 23:54:50 +0800
Subject: [PATCH] eventdev: fix race condition on timer list counter

[ upstream commit aceb737d6f3210556a139514d304bf8f315a043f ]

The n_poll_lcores counter and poll_lcore array are shared between lcores
and the update of these variables are out of the protection of spinlock
on each lcore timer list. The read-modify-write operations of the counter
are not atomic, so it has the potential of race condition between lcores.

Use c11 atomics with RELAXED ordering to prevent confliction.

Fixes: cc7b73ea9e3b ("eventdev: add new software timer adapter")

Signed-off-by: Phil Yang <phil.yang at arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
Acked-by: Erik Gabriel Carrillo <erik.g.carrillo at intel.com>
---
 lib/librte_eventdev/rte_event_timer_adapter.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/lib/librte_eventdev/rte_event_timer_adapter.c b/lib/librte_eventdev/rte_event_timer_adapter.c
index 161e21a68..76885972e 100644
--- a/lib/librte_eventdev/rte_event_timer_adapter.c
+++ b/lib/librte_eventdev/rte_event_timer_adapter.c
@@ -579,6 +579,7 @@ swtim_callback(struct rte_timer *tim)
 	uint16_t nb_evs_invalid = 0;
 	uint64_t opaque;
 	int ret;
+	int n_lcores;
 
 	opaque = evtim->impl_opaque[1];
 	adapter = (struct rte_event_timer_adapter *)(uintptr_t)opaque;
@@ -601,8 +602,12 @@ swtim_callback(struct rte_timer *tim)
 				      "with immediate expiry value");
 		}
 
-		if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore].v)))
-			sw->poll_lcores[sw->n_poll_lcores++] = lcore;
+		if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore].v))) {
+			n_lcores = __atomic_fetch_add(&sw->n_poll_lcores, 1,
+						     __ATOMIC_RELAXED);
+			__atomic_store_n(&sw->poll_lcores[n_lcores], lcore,
+					__ATOMIC_RELAXED);
+		}
 	} else {
 		EVTIM_BUF_LOG_DBG("buffered an event timer expiry event");
 
@@ -1007,6 +1012,7 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
 	uint32_t lcore_id = rte_lcore_id();
 	struct rte_timer *tim, *tims[nb_evtims];
 	uint64_t cycles;
+	int n_lcores;
 
 #ifdef RTE_LIBRTE_EVENTDEV_DEBUG
 	/* Check that the service is running. */
@@ -1029,8 +1035,10 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
 	if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore_id].v))) {
 		EVTIM_LOG_DBG("Adding lcore id = %u to list of lcores to poll",
 			      lcore_id);
-		sw->poll_lcores[sw->n_poll_lcores] = lcore_id;
-		++sw->n_poll_lcores;
+		n_lcores = __atomic_fetch_add(&sw->n_poll_lcores, 1,
+					     __ATOMIC_RELAXED);
+		__atomic_store_n(&sw->poll_lcores[n_lcores], lcore_id,
+				__ATOMIC_RELAXED);
 	}
 
 	ret = rte_mempool_get_bulk(sw->tim_pool, (void **)tims,
-- 
2.20.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-07-24 12:53:52.411591249 +0100
+++ 0100-eventdev-fix-race-condition-on-timer-list-counter.patch	2020-07-24 12:53:48.343007503 +0100
@@ -1,8 +1,10 @@
-From aceb737d6f3210556a139514d304bf8f315a043f Mon Sep 17 00:00:00 2001
+From b01bf3ceeeb3bfe4c1146cb58f92362f279f11f6 Mon Sep 17 00:00:00 2001
 From: Phil Yang <phil.yang at arm.com>
 Date: Tue, 7 Jul 2020 23:54:50 +0800
 Subject: [PATCH] eventdev: fix race condition on timer list counter
 
+[ upstream commit aceb737d6f3210556a139514d304bf8f315a043f ]
+
 The n_poll_lcores counter and poll_lcore array are shared between lcores
 and the update of these variables are out of the protection of spinlock
 on each lcore timer list. The read-modify-write operations of the counter
@@ -11,7 +13,6 @@
 Use c11 atomics with RELAXED ordering to prevent confliction.
 
 Fixes: cc7b73ea9e3b ("eventdev: add new software timer adapter")
-Cc: stable at dpdk.org
 
 Signed-off-by: Phil Yang <phil.yang at arm.com>
 Reviewed-by: Dharmik Thakkar <dharmik.thakkar at arm.com>
@@ -22,10 +23,10 @@
  1 file changed, 12 insertions(+), 4 deletions(-)
 
 diff --git a/lib/librte_eventdev/rte_event_timer_adapter.c b/lib/librte_eventdev/rte_event_timer_adapter.c
-index 232180326..370ea40a7 100644
+index 161e21a68..76885972e 100644
 --- a/lib/librte_eventdev/rte_event_timer_adapter.c
 +++ b/lib/librte_eventdev/rte_event_timer_adapter.c
-@@ -583,6 +583,7 @@ swtim_callback(struct rte_timer *tim)
+@@ -579,6 +579,7 @@ swtim_callback(struct rte_timer *tim)
  	uint16_t nb_evs_invalid = 0;
  	uint64_t opaque;
  	int ret;
@@ -33,7 +34,7 @@
  
  	opaque = evtim->impl_opaque[1];
  	adapter = (struct rte_event_timer_adapter *)(uintptr_t)opaque;
-@@ -605,8 +606,12 @@ swtim_callback(struct rte_timer *tim)
+@@ -601,8 +602,12 @@ swtim_callback(struct rte_timer *tim)
  				      "with immediate expiry value");
  		}
  
@@ -48,7 +49,7 @@
  	} else {
  		EVTIM_BUF_LOG_DBG("buffered an event timer expiry event");
  
-@@ -1011,6 +1016,7 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
+@@ -1007,6 +1012,7 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
  	uint32_t lcore_id = rte_lcore_id();
  	struct rte_timer *tim, *tims[nb_evtims];
  	uint64_t cycles;
@@ -56,7 +57,7 @@
  
  #ifdef RTE_LIBRTE_EVENTDEV_DEBUG
  	/* Check that the service is running. */
-@@ -1033,8 +1039,10 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
+@@ -1029,8 +1035,10 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
  	if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore_id].v))) {
  		EVTIM_LOG_DBG("Adding lcore id = %u to list of lcores to poll",
  			      lcore_id);