eventdev: use C11 atomics for lcore timer armed flag

[dpdk.git] / lib / librte_eventdev / rte_event_timer_adapter.c

diff --git a/lib/librte_eventdev/rte_event_timer_adapter.c b/lib/librte_eventdev/rte_event_timer_adapter.c
index 2321803..4ed3013 100644 (file)
--- a/lib/librte_eventdev/rte_event_timer_adapter.c
+++ b/lib/librte_eventdev/rte_event_timer_adapter.c
@@ -554,7 +554,7 @@ struct swtim {
        uint32_t timer_data_id;
        /* Track which cores have actually armed a timer */
        struct {
-               rte_atomic16_t v;
+               uint16_t v;
        } __rte_cache_aligned in_use[RTE_MAX_LCORE];
        /* Track which cores' timer lists should be polled */
        unsigned int poll_lcores[RTE_MAX_LCORE];
@@ -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 +606,13 @@ 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(sw->in_use[lcore].v == 0)) {
+                       sw->in_use[lcore].v = 1;
+                       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");
 
@@ -829,7 +835,7 @@ swtim_init(struct rte_event_timer_adapter *adapter)
 
        /* Initialize the variables that track in-use timer lists */
        for (i = 0; i < RTE_MAX_LCORE; i++)
-               rte_atomic16_init(&sw->in_use[i].v);
+               sw->in_use[i].v = 0;
 
        /* Initialize the timer subsystem and allocate timer data instance */
        ret = rte_timer_subsystem_init();
@@ -1011,6 +1017,9 @@ __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;
+       /* Timer list for this lcore is not in use. */
+       uint16_t exp_state = 0;
 
 #ifdef RTE_LIBRTE_EVENTDEV_DEBUG
        /* Check that the service is running. */
@@ -1029,12 +1038,18 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
        /* If this is the first time we're arming an event timer on this lcore,
         * mark this lcore as "in use"; this will cause the service
         * function to process the timer list that corresponds to this lcore.
+        * The atomic compare-and-swap operation can prevent the race condition
+        * on in_use flag between multiple non-EAL threads.
         */
-       if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore_id].v))) {
+       if (unlikely(__atomic_compare_exchange_n(&sw->in_use[lcore_id].v,
+                       &exp_state, 1, 0,
+                       __ATOMIC_RELAXED, __ATOMIC_RELAXED))) {
                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,