RDK-588: limit conservative scan range

Source/JavaScriptCore/heap/MachineStackMarker.cpp

@@ -27,6 +27,7 @@
 #include <wtf/BitVector.h>
 #include <wtf/PageBlock.h>
 #include <wtf/StdLibExtras.h>
+#include <wtf/ConservativeScanStackGuards.h>
 
 namespace JSC {
 
@@ -44,7 +45,7 @@ void MachineThreads::gatherFromCurrentThread(ConservativeRoots& conservativeRoot
         conservativeRoots.add(registersBegin, registersEnd, jitStubRoutines, codeBlocks);
     }
 
-    conservativeRoots.add(currentThreadState.stackTop, currentThreadState.stackOrigin, jitStubRoutines, codeBlocks);
+    conservativeRoots.add(currentThreadState.stackTop, WTF::ConservativeScanStackGuards::updatedStackOrigin(currentThreadState.stackTop, currentThreadState.stackOrigin), jitStubRoutines, codeBlocks);
 }
 
 static inline int osRedZoneAdjustment()

Source/WTF/wtf/CMakeLists.txt

@@ -46,6 +46,7 @@ set(WTF_PUBLIC_HEADERS
     ConcurrentPtrHashSet.h
     ConcurrentVector.h
     Condition.h
+    ConservativeScanStackGuards.h
     CountingLock.h
     CrossThreadCopier.h
     CrossThreadQueue.h
@@ -422,6 +423,7 @@ set(WTF_SOURCES
     CompilationThread.cpp
     ConcurrentBuffer.cpp
     ConcurrentPtrHashSet.cpp
+    ConservativeScanStackGuards.cpp
     CountingLock.cpp
     CrossThreadCopier.cpp
     CrossThreadTaskHandler.cpp

Source/WTF/wtf/ConservativeScanStackGuards.cpp

@@ -0,0 +1,6 @@
+#include "ConservativeScanStackGuards.h"
+
+namespace WTF {
+    std::atomic_bool ConservativeScanStackGuards::active {true};
+    thread_local std::deque<void*>  ConservativeScanStackGuards::guard_ptr_stack;
+}

Source/WTF/wtf/ConservativeScanStackGuards.h

@@ -0,0 +1,65 @@
+#pragma once
+
+#include "Logging.h"
+
+#include <atomic>
+#include <deque>
+
+namespace WTF {
+    class ConservativeScanStackGuards {
+        public:
+            struct ConservativeScanStackGuard {
+                ConservativeScanStackGuard() {
+                    ConservativeScanStackGuards::setStackGuard(this);
+                }
+                ~ConservativeScanStackGuard() {
+                    ConservativeScanStackGuards::resetStackGuard(this);
+                }
+
+                private:
+                    // Prevent heap allocation
+                    void *operator new   (size_t);
+                    void *operator new[] (size_t);
+                    void  operator delete   (void *);
+                    void  operator delete[] (void*);
+            };
+
+            friend struct ConservativeScanStackGuard;
+
+            static void* updatedStackOrigin(void *stackTop, void *stackOrigin) {
+                if (!active.load() || guard_ptr_stack.empty()) {
+                    return stackOrigin;
+                }
+
+                void *ret = stackOrigin;
+
+                void *guard_ptr = guard_ptr_stack.back();
+
+                if (guard_ptr > stackTop && guard_ptr < stackOrigin) {
+                    WTFLogAlways("ConservativeScanStackGuards: guard IN RANGE: stackTop: %p guard: %p stackOrigin: %p; correcting stackOrigin\n", stackTop, guard_ptr, stackOrigin);
+                    ret = guard_ptr;
+                }
+                return ret;
+            }
+
+            static void setActive(bool act) {
+                active.store(act);
+            }
+
+        private:
+
+            static thread_local std::deque<void*> guard_ptr_stack;
+            static std::atomic_bool active;
+
+            static void setStackGuard(void *ptr) {
+                guard_ptr_stack.push_back(ptr);
+            }
+
+            static void resetStackGuard(void *ptr) {
+                if (ptr != guard_ptr_stack.back()) {
+                    WTFLogAlways("ConservativeScanStackGuards::resetStackGuard expected %p, had: %p", guard_ptr_stack.back(), ptr);
+                }
+                guard_ptr_stack.pop_back();
+            }
+    };
+}

Source/WTF/wtf/glib/RunLoopGLib.cpp

@@ -31,6 +31,8 @@
 #include <wtf/MainThread.h>
 #include <wtf/glib/RunLoopSourcePriority.h>
 
+#include "wtf/ConservativeScanStackGuards.h"
+
 namespace WTF {
 
 typedef struct {
@@ -103,6 +105,7 @@ void RunLoop::run()
     ASSERT(!runLoop.m_mainLoops.isEmpty());
 
     GMainLoop* innermostLoop = runLoop.m_mainLoops[0].get();
+    ConservativeScanStackGuards::ConservativeScanStackGuard guard;
     if (!g_main_loop_is_running(innermostLoop)) {
         g_main_context_push_thread_default(mainContext);
         g_main_loop_run(innermostLoop);

Source/WebKit/WebProcess/WebProcess.cpp

@@ -1042,6 +1042,10 @@ void WebProcess::isJITEnabled(CompletionHandler<void(bool)>&& completionHandler)
 
 void WebProcess::garbageCollectJavaScriptObjects()
 {
+    {
+        JSLockHolder lock(commonVM());
+        commonVM().shrinkFootprintWhenIdle();
+    }
     GCController::singleton().garbageCollectNow();
 }