[dpdk-dev] [PATCH 1/3] eventdev: fix race condition on timer list counter
From: Phil Yang <hidden>
Date: 2020-06-12 11:20:31
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
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 <redacted>
Reviewed-by: Dharmik Thakkar <redacted>
Reviewed-by: Ruifeng Wang <redacted>
---
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