From 97d4df41542ee64adb65e94414c2d34876edfc1e Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Sun, 2 Oct 2022 19:30:43 +0100
Subject: [PATCH] Better thread safety for zone boundingbox caches.

---
 pcbnew/board.h                   |  1 -
 pcbnew/board_design_settings.cpp |  2 +-
 pcbnew/zone.cpp                  | 13 ++++++++++---
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/pcbnew/board.h b/pcbnew/board.h
index 5ff56af6b6..aeeb7e5408 100644
--- a/pcbnew/board.h
+++ b/pcbnew/board.h
@@ -1151,7 +1151,6 @@ public:
     std::unordered_map< wxString, LSET >                  m_LayerExpressionCache;
     std::unordered_map<ZONE*, std::unique_ptr<DRC_RTREE>> m_CopperZoneRTreeCache;
     std::unique_ptr<DRC_RTREE>                            m_CopperItemRTreeCache;
-
     mutable std::unordered_map<const ZONE*, BOX2I>        m_ZoneBBoxCache;
 
     // ------------ DRC caches -------------
diff --git a/pcbnew/board_design_settings.cpp b/pcbnew/board_design_settings.cpp
index 944d842ca7..59427d82ab 100644
--- a/pcbnew/board_design_settings.cpp
+++ b/pcbnew/board_design_settings.cpp
@@ -181,7 +181,7 @@ BOARD_DESIGN_SETTINGS::BOARD_DESIGN_SETTINGS( JSON_SETTINGS* aParent, const std:
     m_DRCSeverities[ DRCE_TEXT_THICKNESS ] = RPT_SEVERITY_WARNING;
 
     m_DRCSeverities[ DRCE_FOOTPRINT_TYPE_MISMATCH ] = RPT_SEVERITY_IGNORE;
-    
+
     m_DRCSeverities[ DRCE_LIB_FOOTPRINT_ISSUES ] = RPT_SEVERITY_WARNING;
     m_DRCSeverities[ DRCE_LIB_FOOTPRINT_MISMATCH ] = RPT_SEVERITY_WARNING;
 
diff --git a/pcbnew/zone.cpp b/pcbnew/zone.cpp
index 8f95f0a369..0c16a5bfd1 100644
--- a/pcbnew/zone.cpp
+++ b/pcbnew/zone.cpp
@@ -308,16 +308,19 @@ bool ZONE::IsOnLayer( PCB_LAYER_ID aLayer ) const
 
 const BOX2I ZONE::GetBoundingBox() const
 {
-    if( const BOARD* parent = GetBoard() )
+    if( const BOARD* board = GetBoard() )
     {
-        std::unordered_map<const ZONE*, BOX2I>& cache = parent->m_ZoneBBoxCache;
+        std::unordered_map<const ZONE*, BOX2I>& cache = board->m_ZoneBBoxCache;
         auto                                    cacheIter = cache.find( this );
 
         if( cacheIter != cache.end() )
             return cacheIter->second;
 
         BOX2I bbox = m_Poly->BBox();
+
+        std::unique_lock<std::mutex> cacheLock( const_cast<BOARD*>( board )->m_CachesMutex );
         cache[ this ] = bbox;
+
         return bbox;
     }
 
@@ -327,12 +330,16 @@ const BOX2I ZONE::GetBoundingBox() const
 
 void ZONE::CacheBoundingBox()
 {
-    std::unordered_map<const ZONE*, BOX2I>& cache = GetBoard()->m_ZoneBBoxCache;
+    BOARD*                                  board = GetBoard();
+    std::unordered_map<const ZONE*, BOX2I>& cache = board->m_ZoneBBoxCache;
 
     auto cacheIter = cache.find( this );
 
     if( cacheIter == cache.end() )
+    {
+        std::unique_lock<std::mutex> cacheLock( board->m_CachesMutex );
         cache[ this ] = m_Poly->BBox();
+    }
 }