[PATCH 1/2] rcu: use atomic operation on acked token

[PATCH 1/2] rcu: use atomic operation on acked token

[Honnappa Nagarahalli]

acked_token should be read using atomic operation as the
the API rte_rcu_qsbr_check is advertised as multi-thread safe.

Fixes: 1f90d32ce175 ("rcu: add least acknowledged token optimization")
Cc: stable@dpdk.org

Reported-by: Ola Liljedahl <ola.liljedahl@arm.com>
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
---
 lib/rcu/rte_rcu_qsbr.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/rcu/rte_rcu_qsbr.h b/lib/rcu/rte_rcu_qsbr.h
index 5979fb0efb..f6a3731308 100644
--- a/lib/rcu/rte_rcu_qsbr.h
+++ b/lib/rcu/rte_rcu_qsbr.h
@@ -667,7 +667,8 @@ rte_rcu_qsbr_check(struct rte_rcu_qsbr *v, uint64_t t, bool wait)
 	RTE_ASSERT(v != NULL);
 
 	/* Check if all the readers have already acknowledged this token */
-	if (likely(t <= v->acked_token)) {
+	if (likely(t <= rte_atomic_load_explicit(&v->acked_token,
+						rte_memory_order_relaxed))) {
 		__RTE_RCU_DP_LOG(DEBUG,
 			"%s: check: token = %" PRIu64 ", wait = %d",
 			__func__, t, wait);
-- 
2.34.1

[PATCH 2/2] rcu: use correct value of acked token in debug print

[Honnappa Nagarahalli]

Debug print should use acked token value that was used for comparison.

Fixes: bf386ae377aa ("rcu: add additional debug logs")
Cc: stable@dpdk.org

Reported-by: Nathan Brown <nathan.brown@arm.com>
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Nathan Brown <nathan.brown@arm.com>
---
 lib/rcu/rte_rcu_qsbr.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/rcu/rte_rcu_qsbr.h b/lib/rcu/rte_rcu_qsbr.h
index f6a3731308..a7d6e63560 100644
--- a/lib/rcu/rte_rcu_qsbr.h
+++ b/lib/rcu/rte_rcu_qsbr.h
@@ -664,17 +664,20 @@ __rte_rcu_qsbr_check_all(struct rte_rcu_qsbr *v, uint64_t t, bool wait)
 static __rte_always_inline int
 rte_rcu_qsbr_check(struct rte_rcu_qsbr *v, uint64_t t, bool wait)
 {
+	uint64_t acked_token;
+
 	RTE_ASSERT(v != NULL);
 
 	/* Check if all the readers have already acknowledged this token */
-	if (likely(t <= rte_atomic_load_explicit(&v->acked_token,
-						rte_memory_order_relaxed))) {
+	acked_token = rte_atomic_load_explicit(&v->acked_token,
+						rte_memory_order_relaxed);
+	if (likely(t <= acked_token)) {
 		__RTE_RCU_DP_LOG(DEBUG,
 			"%s: check: token = %" PRIu64 ", wait = %d",
 			__func__, t, wait);
 		__RTE_RCU_DP_LOG(DEBUG,
 			"%s: status: least acked token = %" PRIu64,
-			__func__, v->acked_token);
+			__func__, acked_token);
 		return 1;
 	}
 
-- 
2.34.1

Re: [PATCH 2/2] rcu: use correct value of acked token in debug print

[Thomas Monjalon]

05/02/2024 05:59, Honnappa Nagarahalli:
> Debug print should use acked token value that was used for comparison.
> 
> Fixes: bf386ae377aa ("rcu: add additional debug logs")
> Cc: stable@dpdk.org
> 
> Reported-by: Nathan Brown <nathan.brown@arm.com>
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Nathan Brown <nathan.brown@arm.com>

We trust you about RCU :)

Series applied, thanks.