[dpdk-stable] [PATCH] lib/rcu: fix possible spurious thread unregister

[Ruifeng Wang]

Thread unregister returns success while unregister not been performed.
This is due to incorrect thread registration status check.
Fix this issue by correcting bitmap check.

Fixes: 64994b56cfd7 ("rcu: add RCU library supporting QSBR mechanism")
Cc: stable at dpdk.org

Signed-off-by: Ruifeng Wang <ruifeng.wang at arm.com>
Reviewed-by: Gavin Hu <gavin.hu at arm.com>
---
 lib/librte_rcu/rte_rcu_qsbr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/librte_rcu/rte_rcu_qsbr.c b/lib/librte_rcu/rte_rcu_qsbr.c
index ce7f93dd3..8c37c88cd 100644
--- a/lib/librte_rcu/rte_rcu_qsbr.c
+++ b/lib/librte_rcu/rte_rcu_qsbr.c
@@ -158,7 +158,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr *v, unsigned int thread_id)
 	/* Check if the thread is already unregistered */
 	old_bmap = __atomic_load_n(__RTE_QSBR_THRID_ARRAY_ELM(v, i),
 					__ATOMIC_RELAXED);
-	if (old_bmap & ~(1UL << id))
+	if (!(old_bmap & (1UL << id)))
 		return 0;
 
 	do {
@@ -175,7 +175,7 @@ rte_rcu_qsbr_thread_unregister(struct rte_rcu_qsbr *v, unsigned int thread_id)
 		if (success)
 			__atomic_fetch_sub(&v->num_threads,
 						1, __ATOMIC_RELAXED);
-		else if (old_bmap & ~(1UL << id))
+		else if (!(old_bmap & (1UL << id)))
 			/* Someone else unregistered this thread.
 			 * Counter should not be incremented.
 			 */
-- 
2.17.1