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From: Phil Yang <phil.yang@arm.com>
To: dev@dpdk.org,
erik.g.carrillo@intel.com
Cc: drc@linux.vnet.ibm.com, honnappa.nagarahalli@arm.com, ruifeng.wang@arm.com,
dharmik.thakkar@arm.com, nd@arm.com, stable@dpdk.org
Date: Fri, 12 Jun 2020 19:19:56 +0800
Message-Id: <1591960798-24024-1-git-send-email-phil.yang@arm.com>
X-Mailer: git-send-email 2.7.4
Subject: [dpdk-dev] [PATCH 1/3] eventdev: fix race condition on timer list
counter
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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