From f7624c4afd92584e0f003da503c658d9c019af92 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Mon, 4 Dec 2023 12:19:43 -0800
Subject: [PATCH] Handled persistent session mutex relinquish correctly

---
 Common/app/mqtt/mqtt_agent_task.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/Common/app/mqtt/mqtt_agent_task.c b/Common/app/mqtt/mqtt_agent_task.c
index 23bdc238..9ae8ec99 100644
--- a/Common/app/mqtt/mqtt_agent_task.c
+++ b/Common/app/mqtt/mqtt_agent_task.c
@@ -587,7 +587,7 @@ static void prvResubscribeCommandCallback( MQTTAgentCommandContext_t * pxCommand
 static MQTTStatus_t prvHandleResubscribe( MQTTAgentContext_t * pxMqttAgentCtx,
                                           SubMgrCtx_t * pxCtx )
 {
-    MQTTStatus_t xStatus = MQTTSuccess;
+    MQTTStatus_t xStatus;
 
     configASSERT( pxCtx );
     configASSERT( pxCtx->xMutex );
@@ -597,7 +597,7 @@ static MQTTStatus_t prvHandleResubscribe( MQTTAgentContext_t * pxMqttAgentCtx,
                                  pxCtx->pxCallbacks,
                                  &( pxCtx->uxSubscriptionCount ) );
 
-    if( ( xStatus == MQTTSuccess ) && ( pxCtx->uxSubscriptionCount > 0U ) )
+    if( pxCtx->uxSubscriptionCount > 0U )
     {
         MQTTAgentCommandInfo_t xCommandParams =
         {
@@ -1154,11 +1154,25 @@ void vMQTTAgentTask( void * pvParameters )
                 xMQTTStatus = MQTTAgent_ResumeSession( &( pxCtx->xAgentContext ), xSessionPresent );
 
                 /* Re-subscribe to all the previously subscribed topics if there is no existing session. */
-                if( ( xMQTTStatus == MQTTSuccess ) &&
-                    ( xSessionPresent == false ) )
+                if( xMQTTStatus == MQTTSuccess )
                 {
-                    xMQTTStatus = prvHandleResubscribe( &( pxCtx->xAgentContext ),
-                                                        &( pxCtx->xSubMgrCtx ) );
+                    if( xSessionPresent == false )
+                    {
+                        xMQTTStatus = prvHandleResubscribe( &( pxCtx->xAgentContext ),
+                                                            &( pxCtx->xSubMgrCtx ) );
+                    }
+                    else
+                    {
+                        /* No need to resubscribe as a session is present and the broker is aware of
+                         * the previous subscriptions. */
+                        if( MUTEX_IS_OWNED( pxCtx->xSubMgrCtx.xMutex ) )
+                        {
+                            /* Give the mutex as there is no subscribe command pending. */
+                            ( void ) xUnlockSubCtx( &( pxCtx->xSubMgrCtx ) );
+                        }
+
+                        LogInfo( "Session already present (no re-subscription)." );
+                    }
                 }
             }
             else if( xMQTTStatus == MQTTSuccess )