Addendum to a9be1ec - it's more complex than it seemed, .. (read below)

20a14e8 exposed previously hidden GTA bugs that are correlated to BLOCKING_LOAD states. As it turns out, the whole "Blocking load" workaround concept across the codebase is primarily to avoid freezes, and these "Susoension lines / vehicle handling" code sites are at the roots of it, and yet they were always still causing game freezes. I'm slowly addressing it, this and a9be1ec is part of it, im still to go deeper, but these 2 commits should at least allow for more blocking/non blocking load manipulation as they'd be the first underlying issues to hit, and should now be resolved.

Author: Dutchman101

Client/game_sa/CModelInfoSA.cpp

@@ -1280,11 +1280,15 @@ unsigned int CModelInfoSA::GetNumRemaps()
 
 void* CModelInfoSA::GetVehicleSuspensionData()
 {
+    if (!GetInterface()->pColModel || !GetInterface()->pColModel->m_data)
+        return nullptr;
     return GetInterface()->pColModel->m_data->m_suspensionLines;
 }
 
 void* CModelInfoSA::SetVehicleSuspensionData(void* pSuspensionLines)
 {
+    if (!GetInterface()->pColModel || !GetInterface()->pColModel->m_data)
+        return nullptr;
     CColDataSA* pColData = GetInterface()->pColModel->m_data;
     void*       pOrigSuspensionLines = pColData->m_suspensionLines;
     pColData->m_suspensionLines = reinterpret_cast<CColLineSA*>(pSuspensionLines);
@@ -1617,7 +1621,7 @@ void CModelInfoSA::RestoreColModel()
 
         // Force the game to load the original collision model data, if we applied a custom collision model before
         // there was any object/building, which would've provoked CColStore to request it.
-        if (!m_pInterface->pColModel->m_data && m_dwReferences > 1)
+        if (m_pInterface->pColModel && !m_pInterface->pColModel->m_data && m_dwReferences > 1)
         {
             pGame->GetStreaming()->RemoveModel(RESOURCE_ID_COL + m_pInterface->pColModel->m_sphere.m_collisionSlot);
         }

Client/game_sa/CPhysicalSA.cpp

@@ -22,9 +22,14 @@ CRect* CPhysicalSAInterface::GetBoundRect_(CRect* pRect)
 {
     CVector boundCentre;
     CEntitySAInterface::GetBoundCentre(&boundCentre);
-    float fRadius = CModelInfoSAInterface::GetModelInfo(m_nModelIndex)->pColModel->m_sphere.m_radius;
+    CBaseModelInfoSAInterface* pModelInfo = CModelInfoSAInterface::GetModelInfo(m_nModelIndex);
+
+    if (!pModelInfo || !pModelInfo->pColModel)
+        return pRect;
+
+    float fRadius = pModelInfo->pColModel->m_sphere.m_radius;
     *pRect = CRect(boundCentre.fX - fRadius, boundCentre.fY - fRadius, boundCentre.fX + fRadius, boundCentre.fY + fRadius);
-    pRect->FixIncorrectTopLeft();            // Fix #1613: custom map collision crashes in CPhysical class (infinite loop)
+    pRect->FixIncorrectTopLeft(); // Fix #1613: custom map collision crashes in CPhysical class (infinite loop)
     return pRect;
 }
 

Client/game_sa/CVehicleSA.cpp

@@ -1350,10 +1350,21 @@ CFlyingHandlingEntry* CVehicleSA::GetFlyingHandlingData()
 
 void CVehicleSA::SetHandlingData(CHandlingEntry* pHandling)
 {
+    if (!pHandling)
+        return;
+
+    CVehicleSAInterface* pVehicleInterface = GetVehicleInterface();
+    if (!pVehicleInterface)
+        return;
+
     // Store the handling and recalculate it
     m_pHandlingData = static_cast<CHandlingEntrySA*>(pHandling);
-    GetVehicleInterface()->pHandlingData = m_pHandlingData->GetInterface();
-    RecalculateHandling();
+    pVehicleInterface->pHandlingData = m_pHandlingData->GetInterface();
+    
+    // Only recalculate if collision model is loaded (needed for suspension lines)
+    CModelInfo* pModelInfo = pGame->GetModelInfo(GetModelIndex());
+    if (pModelInfo && pModelInfo->GetInterface()->pColModel && pModelInfo->GetInterface()->pColModel->m_data)
+        RecalculateHandling();
 }
 
 void CVehicleSA::SetFlyingHandlingData(CFlyingHandlingEntry* pFlyingHandling)
@@ -1369,13 +1380,24 @@ void CVehicleSA::RecalculateHandling()
     if (!m_pHandlingData)
         return;
 
+    // Validate vehicle interface
+    CVehicleSAInterface* pInt = GetVehicleInterface();
+    if (!pInt)
+        return;
+
+    // Ensure collision model is loaded before recalculating (needed for suspension lines)
+    CModelInfo* pModelInfo = pGame->GetModelInfo(GetModelIndex());
+    if (!pModelInfo || !pModelInfo->GetInterface()->pColModel || !pModelInfo->GetInterface()->pColModel->m_data)
+        return;
+
     m_pHandlingData->Recalculate();
 
-    // Recalculate the suspension lines
-    RecalculateSuspensionLines();
+    // Recalculate the suspension lines (only for vehicles that have suspension)
+    // Already validated that pColModel and m_data exist above
+    if (pModelInfo->IsCar() || pModelInfo->IsMonsterTruck() || pModelInfo->IsTrailer() || pModelInfo->IsBike())
+        RecalculateSuspensionLines();
 
     // Put it in our interface
-    CVehicleSAInterface* pInt = GetVehicleInterface();
     unsigned int         uiHandlingFlags = m_pHandlingData->GetInterface()->uiHandlingFlags;
     bool                 hydralicsInstalled = false, nitroInstalled = false;
 
@@ -1758,6 +1780,11 @@ void* CVehicleSA::GetPrivateSuspensionLines()
     if (m_pSuspensionLines == NULL)
     {
         CModelInfo* pModelInfo = pGame->GetModelInfo(GetModelIndex());
+        // pColModel can be NULL if collision data hasn't been streamed in yet.
+        // GTA SA loads visual models and collision models separately via CColStore.
+        // The model can be marked as "loaded" even if collision data is still pending.
+        if (!pModelInfo->GetInterface()->pColModel || !pModelInfo->GetInterface()->pColModel->m_data)
+            return NULL;
         CColDataSA* pColData = pModelInfo->GetInterface()->pColModel->m_data;
         if (pModelInfo->IsMonsterTruck())
         {
@@ -1782,6 +1809,9 @@ void* CVehicleSA::GetPrivateSuspensionLines()
 void CVehicleSA::CopyGlobalSuspensionLinesToPrivate()
 {
     CModelInfo* pModelInfo = pGame->GetModelInfo(GetModelIndex());
+    // Collision model may not be loaded yet (see GetPrivateSuspensionLines)
+    if (!pModelInfo->GetInterface()->pColModel || !pModelInfo->GetInterface()->pColModel->m_data)
+        return;
     CColDataSA* pColData = pModelInfo->GetInterface()->pColModel->m_data;
     if (pModelInfo->IsMonsterTruck())
     {
@@ -1815,8 +1845,14 @@ void CVehicleSA::RecalculateSuspensionLines()
         if (pModelInfo->IsTrain() || dwModel == 571 || dwModel == 570 || dwModel == 569 || dwModel == 590)
             return;
 
-        GetVehicleInterface()->SetupSuspensionLines();
+        // Ensure collision model is loaded before setting up suspension
+        if (!pModelInfo->GetInterface()->pColModel || !pModelInfo->GetInterface()->pColModel->m_data)
+            return;
 
+        // Note: We skip calling SetupSuspensionLines() because it's GTA SA's native code that can
+        // access pColModel->m_data without validation. If collision model is unloaded during execution
+        // (race condition), it causes crashes. CopyGlobalSuspensionLinesToPrivate() is safer as it
+        // validates collision model before accessing.
         CopyGlobalSuspensionLinesToPrivate();
     }
 }

Client/mods/deathmatch/logic/CClientVehicle.cpp

@@ -4305,6 +4305,10 @@ void CClientVehicle::ApplyHandling()
     if (!pModelInfo || !pModelInfo->IsLoaded())
         return;
 
+    // Ensure collision model is loaded before recalculating (needed for suspension lines)
+    if (!pModelInfo->GetInterface()->pColModel || !pModelInfo->GetInterface()->pColModel->m_data)
+        return;
+
     m_pVehicle->RecalculateHandling();
 
     if (m_eVehicleType == CLIENTVEHICLE_BMX || m_eVehicleType == CLIENTVEHICLE_BIKE)