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* [dpdk-stable] [PATCH 1/3] eventdev: fix race condition on timer list counter
@ 2020-06-12 11:19 Phil Yang
  2020-06-18 15:17 ` Carrillo, Erik G
  2020-07-02  5:26 ` [dpdk-stable] [PATCH v2 1/4] " Phil Yang
  0 siblings, 2 replies; 19+ messages in thread
From: Phil Yang @ 2020-06-12 11:19 UTC (permalink / raw)
  To: dev, erik.g.carrillo
  Cc: drc, honnappa.nagarahalli, ruifeng.wang, dharmik.thakkar, nd, stable

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")
Cc: erik.g.carrillo@intel.com
Cc: stable@dpdk.org

Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.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 005459f..6a0e283 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)
 	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;
@@ -605,8 +606,12 @@ 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");
 
@@ -1011,6 +1016,7 @@ __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. */
@@ -1033,8 +1039,10 @@ __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,
-- 
2.7.4


^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2020-07-08 15:01 UTC | newest]

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-12 11:19 [dpdk-stable] [PATCH 1/3] eventdev: fix race condition on timer list counter Phil Yang
2020-06-18 15:17 ` Carrillo, Erik G
2020-06-18 18:25   ` Honnappa Nagarahalli
2020-06-22  9:48     ` Phil Yang
2020-07-01 11:22       ` [dpdk-stable] [dpdk-dev] " Jerin Jacob
2020-07-02  3:28         ` Phil Yang
2020-07-02  3:26     ` [dpdk-stable] " Phil Yang
2020-07-02  3:56       ` Honnappa Nagarahalli
2020-07-02 21:15         ` Carrillo, Erik G
2020-07-02 21:30           ` Honnappa Nagarahalli
2020-06-22  9:09   ` Phil Yang
2020-07-02  5:26 ` [dpdk-stable] [PATCH v2 1/4] " Phil Yang
2020-07-07 11:13   ` [dpdk-stable] [PATCH v3 " Phil Yang
2020-07-07 15:54     ` [dpdk-stable] [PATCH v4 " Phil Yang
2020-07-07 15:54       ` [dpdk-stable] [PATCH v4 2/4] eventdev: use C11 atomics for lcore timer armed flag Phil Yang
2020-07-07 15:54       ` [dpdk-stable] [PATCH v4 3/4] eventdev: remove redundant code Phil Yang
2020-07-07 15:54       ` [dpdk-stable] [PATCH v4 4/4] eventdev: relax smp barriers with C11 atomics Phil Yang
2020-07-08 13:30       ` [dpdk-stable] [dpdk-dev] [PATCH v4 1/4] eventdev: fix race condition on timer list counter Jerin Jacob
2020-07-08 15:01         ` Thomas Monjalon

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