The num_mapped_cores and execute_lock are synchronized with rte_atomic_XX
APIs which is a full barrier, DMB, on aarch64. This patch optimized it with
c11 atomic one-way barrier.
Signed-off-by: Phil Yang <phil.y...@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
Reviewed-by: Gavin Hu <gavin...@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
---
lib/librte_eal/common/rte_service.c | 50 ++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 15 deletions(-)
diff --git a/lib/librte_eal/common/rte_service.c
b/lib/librte_eal/common/rte_service.c
index 670f5a9..96a59b6 100644
--- a/lib/librte_eal/common/rte_service.c
+++ b/lib/librte_eal/common/rte_service.c
@@ -42,7 +42,7 @@ struct rte_service_spec_impl {
* running this service callback. When not set, a core may take the
* lock and then run the service callback.
*/
- rte_atomic32_t execute_lock;
+ uint32_t execute_lock;
/* API set/get-able variables */
int8_t app_runstate;
@@ -54,7 +54,7 @@ struct rte_service_spec_impl {
* It does not indicate the number of cores the service is running
* on currently.
*/
- rte_atomic32_t num_mapped_cores;
+ int32_t num_mapped_cores;
uint64_t calls;
uint64_t cycles_spent;
} __rte_cache_aligned;
@@ -329,7 +329,8 @@ rte_service_runstate_get(uint32_t id)
rte_smp_rmb();
int check_disabled = !(s->internal_flags & SERVICE_F_START_CHECK);
- int lcore_mapped = (rte_atomic32_read(&s->num_mapped_cores) > 0);
+ int lcore_mapped = (__atomic_load_n(&s->num_mapped_cores,
+ __ATOMIC_RELAXED) > 0);
return (s->app_runstate == RUNSTATE_RUNNING) &&
(s->comp_runstate == RUNSTATE_RUNNING) &&
@@ -372,11 +373,20 @@ service_run(uint32_t i, struct core_state *cs, uint64_t
service_mask,
cs->service_active_on_lcore[i] = 1;
if ((service_mt_safe(s) == 0) && (serialize_mt_unsafe == 1)) {
- if (!rte_atomic32_cmpset((uint32_t *)&s->execute_lock, 0, 1))
+ uint32_t expected = 0;
+ /* ACQUIRE ordering here is to prevent the callback
+ * function from hoisting up before the execute_lock
+ * setting.
+ */
+ if (!__atomic_compare_exchange_n(&s->execute_lock, &expected, 1,
+ 0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED))
return -EBUSY;
service_runner_do_callback(s, cs, i);
- rte_atomic32_clear(&s->execute_lock);
+ /* RELEASE ordering here is used to pair with ACQUIRE
+ * above to achieve lock semantic.
+ */
+ __atomic_store_n(&s->execute_lock, 0, __ATOMIC_RELEASE);
} else
service_runner_do_callback(s, cs, i);
@@ -412,11 +422,11 @@ rte_service_run_iter_on_app_lcore(uint32_t id, uint32_t
serialize_mt_unsafe)
/* Increment num_mapped_cores to indicate that the service
* is running on a core.
*/
- rte_atomic32_inc(&s->num_mapped_cores);
+ __atomic_add_fetch(&s->num_mapped_cores, 1, __ATOMIC_ACQUIRE);
int ret = service_run(id, cs, UINT64_MAX, s, serialize_mt_unsafe);
- rte_atomic32_dec(&s->num_mapped_cores);
+ __atomic_sub_fetch(&s->num_mapped_cores, 1, __ATOMIC_RELEASE);
return ret;
}
@@ -549,24 +559,32 @@ service_update(uint32_t sid, uint32_t lcore,
uint64_t sid_mask = UINT64_C(1) << sid;
if (set) {
- uint64_t lcore_mapped = lcore_states[lcore].service_mask &
- sid_mask;
+ /* When multiple threads try to update the same lcore
+ * service concurrently, e.g. set lcore map followed
+ * by clear lcore map, the unsynchronized service_mask
+ * values have issues on the num_mapped_cores value
+ * consistency. So we use ACQUIRE ordering to pair with
+ * the RELEASE ordering to synchronize the service_mask.
+ */
+ uint64_t lcore_mapped = __atomic_load_n(
+ &lcore_states[lcore].service_mask,
+ __ATOMIC_ACQUIRE) & sid_mask;
if (*set && !lcore_mapped) {
lcore_states[lcore].service_mask |= sid_mask;
- rte_atomic32_inc(&rte_services[sid].num_mapped_cores);
+ __atomic_add_fetch(&rte_services[sid].num_mapped_cores,
+ 1, __ATOMIC_RELEASE);
}
if (!*set && lcore_mapped) {
lcore_states[lcore].service_mask &= ~(sid_mask);
- rte_atomic32_dec(&rte_services[sid].num_mapped_cores);
+ __atomic_sub_fetch(&rte_services[sid].num_mapped_cores,
+ 1, __ATOMIC_RELEASE);
}
}
if (enabled)
*enabled = !!(lcore_states[lcore].service_mask & (sid_mask));
- rte_smp_wmb();
-
return 0;
}
@@ -622,7 +640,8 @@ rte_service_lcore_reset_all(void)
}
}
for (i = 0; i < RTE_SERVICE_NUM_MAX; i++)
- rte_atomic32_set(&rte_services[i].num_mapped_cores, 0);
+ __atomic_store_n(&rte_services[i].num_mapped_cores, 0,
+ __ATOMIC_RELAXED);
rte_smp_wmb();
@@ -705,7 +724,8 @@ rte_service_lcore_stop(uint32_t lcore)
int32_t enabled = service_mask & (UINT64_C(1) << i);
int32_t service_running = rte_service_runstate_get(i);
int32_t only_core = (1 ==
- rte_atomic32_read(&rte_services[i].num_mapped_cores));
+ __atomic_load_n(&rte_services[i].num_mapped_cores,
+ __ATOMIC_RELAXED));
/* if the core is mapped, and the service is running, and this
* is the only core that is mapped, the service would cease to
--
2.7.4
