Document the conditional signal (WOLFMQTT_USE_COND_SIGNAL).

README.md

@@ -185,7 +185,7 @@ We setup an AWS IoT endpoint and testing device certificate for testing. The AWS
 
 ### Watson IoT Example
 This example enables the wolfMQTT client to connect to the IBM Watson Internet of Things (WIOT) Platform. The WIOT Platform has a limited test broker called "Quickstart" that allows non-secure connections to exercise the component. The example is located in `/examples/wiot/`. Works with MQTT v5 support enabled.
-**NOTE** The WIOT Platform will be disabled DEC2023. The demo may still be useful for users of IBM Watson IOT. 
+**NOTE** The WIOT Platform will be disabled DEC2023. The demo may still be useful for users of IBM Watson IOT.
 
 ### MQTT-SN Example
 The Sensor Network client implements the MQTT-SN protocol for low-bandwidth networks. There are several differences from MQTT, including the ability to use a two byte Topic ID instead the full topic during subscribe and publish. The SN client requires an MQTT-SN gateway. The gateway acts as an intermediary between the SN clients and the broker. This client was tested with the Eclipse Paho MQTT-SN Gateway, which connects by default to the public Eclipse broker, much like our wolfMQTT Client example. The address of the gateway must be configured as the host. The example is located in `/examples/sn-client/`.
@@ -195,6 +195,8 @@ More about MQTT-SN examples in [examples/sn-client/README.md](examples/sn-client
 ### Multithread Example
 This example exercises the multithreading capabilities of the client library. The client implements two tasks: one that publishes to the broker; and another that waits for messages from the broker. The publish thread is created `NUM_PUB_TASKS` times (10 by default) and sends unique messages to the broker. This feature is enabled using the `--enable-mt` configuration option. The example is located in `/examples/multithread/`.
 
+The multi-threading feature can also be used with the non-blocking socket (--enable-nb). If you are having issues with thread synchronization on Linux consider using the conditional signal (`WOLFMQTT_USE_COND_SIGNAL`).
+
 ### Atomic publish and subscribe examples
 In the `examples/pub-sub` folder, there are two simple client examples:
 * mqtt-pub - publishes to a topic
@@ -258,7 +260,7 @@ The initially supported version with full specification support for all features
 
 ### MQTT v5.0 Specification Support
 
-The wolfMQTT client supports connecting to v5 enabled brokers when configured with the `--enable-v5` option. 
+The wolfMQTT client supports connecting to v5 enabled brokers when configured with the `--enable-v5` option.
 The following v5.0 specification features are supported by the wolfMQTT client:
 * AUTH packet
 * User properties