net: lib: coap_client: Remove unnecessary atomic variable

In receiving thread, continuing the loops is based on
has_ongoing_exchanges() so it does not need atomic
coap_client_recv_active variable.

When idling, it wakes from semaphore. But there was potential
deadlock when coap_client_schedule_poll() would not signal the
semaphore, if atomic variable was already showing that it runs.
Removing the atomic variable removes this deadlock.

Signed-off-by: Seppo Takalo <seppo.takalo@nordicsemi.no>

Author: SeppoTakalo

subsys/net/lib/coap/coap_client.c

@@ -24,7 +24,6 @@ static K_MUTEX_DEFINE(coap_client_mutex);
 static struct coap_client *clients[CONFIG_COAP_CLIENT_MAX_INSTANCES];
 static int num_clients;
 static K_SEM_DEFINE(coap_client_recv_sem, 0, 1);
-static atomic_t coap_client_recv_active;
 
 static bool timeout_expired(struct coap_client_internal_request *internal_req);
 static void cancel_requests_with(struct coap_client *client, int error);
@@ -82,10 +81,7 @@ static int coap_client_schedule_poll(struct coap_client *client, int sock,
 	memcpy(&internal_req->coap_request, req, sizeof(struct coap_client_request));
 	internal_req->request_ongoing = true;
 
-	if (!coap_client_recv_active) {
-		k_sem_give(&coap_client_recv_sem);
-	}
-	atomic_set(&coap_client_recv_active, 1);
+	k_sem_give(&coap_client_recv_sem);
 
 	return 0;
 }
@@ -956,7 +952,6 @@ static void cancel_requests_with(struct coap_client *client, int error)
 			reset_internal_request(&client->requests[i]);
 		}
 	}
-	atomic_clear(&coap_client_recv_active);
 	k_mutex_unlock(&client->lock);
 
 }
@@ -974,7 +969,6 @@ void coap_client_recv(void *coap_cl, void *a, void *b)
 
 	k_sem_take(&coap_client_recv_sem, K_FOREVER);
 	while (true) {
-		atomic_set(&coap_client_recv_active, 1);
 		ret = handle_poll();
 		if (ret < 0) {
 			/* Error in polling */
@@ -987,7 +981,6 @@ void coap_client_recv(void *coap_cl, void *a, void *b)
 			continue;
 		} else {
 idle:
-			atomic_set(&coap_client_recv_active, 0);
 			k_sem_take(&coap_client_recv_sem, K_FOREVER);
 		}
 	}