[browser][coreCLR] finalizer on a browser event loop#123629

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Merged

pavelsavara merged 32 commits into dotnet:main from pavelsavara:browser_finalizer

Feb 2, 2026

src/coreclr/vm/ceemain.cpp

-Original file line number
+Diff line change
@@ Expand Up / @@ -921,9 +921,6 @@ void EEStartupHelper() @@
  // On windows the finalizer thread is already partially created and is waiting
  // right before doing HasStarted(). We will release it now.
  FinalizerThread::EnableFinalization();
-#elif defined(TARGET_WASM)
- // on wasm we need to run finalizers on main thread as we are single threaded
- // active issue: https://github.com/dotnet/runtime/issues/114096
 #else
  // This isn't done as part of InitializeGarbageCollector() above because
  // debugger must be initialized before creating EE thread objects
@@ Expand Down @@

src/coreclr/vm/finalizerthread.cpp

-Original file line number
+Diff line change
@@ Expand Up / @@ -40,12 +40,43 @@ bool FinalizerThread::IsCurrentThreadFinalizer() @@
  return GetThreadNULLOk() == g_pFinalizerThread;
 }
+#ifdef TARGET_BROWSER
+extern "C" void SystemJS_ScheduleFinalization();
+extern "C" void SystemJS_ExecuteFinalizationCallback()
+{
+ CONTRACTL
+ {
+ NOTHROW;
+ GC_TRIGGERS;
+ MODE_PREEMPTIVE;
+ }
+ CONTRACTL_END;
+ INSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP;
+ {
+ GCX_COOP();
+ // TODO-WASM https://github.com/dotnet/runtime/issues/123712
+ // ManagedThreadBase::KickOff(FinalizerThread::FinalizerThreadWorkerIteration, NULL);
+ }
+ UNINSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP;
+}
+#endif // TARGET_BROWSER
 void FinalizerThread::EnableFinalization()
 {
  WRAPPER_NO_CONTRACT;
 #ifndef TARGET_WASM
  hEventFinalizer->Set();
+#else // !TARGET_WASM
+#ifdef TARGET_BROWSER
+ SystemJS_ScheduleFinalization();
+#else
+ // WASI is not implemented yet
+#endif // TARGET_BROWSER
 #endif // !TARGET_WASM
 }
@@ Expand DownExpand Up @@
  }
 }
-static BOOL s_FinalizerThreadOK = FALSE;
-static BOOL s_InitializedFinalizerThreadForPlatform = FALSE;
+static bool s_FinalizerThreadOK = false;
+static bool s_InitializedFinalizerThreadForPlatform = false;
+static bool s_PriorityBoosted = false;
 VOID FinalizerThread::FinalizerThreadWorker(void *args)
 {
- BOOL bPriorityBoosted = FALSE;
+ CONTRACTL
+ {
+ THROWS;
+ GC_TRIGGERS;
+ MODE_COOPERATIVE;
+ }
+ CONTRACTL_END;
  while (!fQuitFinalizer)
  {
- // Wait for work to do...
+ FinalizerThread::FinalizerThreadWorkerIteration(nullptr);
+ }
+ if (s_InitializedFinalizerThreadForPlatform)
+ Thread::CleanUpForManagedThreadInNative(GetFinalizerThread());
+}
+VOID FinalizerThread::FinalizerThreadWorkerIteration(void *args)
+{
+ CONTRACTL
+ {
+ THROWS;
+ GC_TRIGGERS;
+ MODE_COOPERATIVE;
+ }
+ CONTRACTL_END;
- _ASSERTE(GetFinalizerThread()->PreemptiveGCDisabled());
 #ifdef _DEBUG
-if (g_pConfig->FastGCStressLevel())
-{
-GetFinalizerThread()->m_GCOnTransitionsOK = FALSE;
-}
+ if (g_pConfig->FastGCStressLevel())
+ {
+ GetFinalizerThread()->m_GCOnTransitionsOK = FALSE;
+ }
 #endif
-GetFinalizerThread()->EnablePreemptiveGC();
+ GetFinalizerThread()->EnablePreemptiveGC();
 #ifdef _DEBUG
-if (g_pConfig->FastGCStressLevel())
-{
-GetFinalizerThread()->m_GCOnTransitionsOK = TRUE;
-}
+ if (g_pConfig->FastGCStressLevel())
+ {
+ GetFinalizerThread()->m_GCOnTransitionsOK = TRUE;
+ }
 #endif
+#ifndef TARGET_WASM
 #if 0
-// Setting the event here, instead of at the bottom of the loop, could
-// cause us to skip draining the Q, if the request is made as soon as
-// the app starts running.
-SignalFinalizationDone();
+ // Setting the event here, instead of at the bottom of the loop, could
+ // cause us to skip draining the Q, if the request is made as soon as
+ // the app starts running.
+ SignalFinalizationDone();
 #endif //0
- WaitForFinalizerEvent (hEventFinalizer);
+ // Wait for work to do...
+ WaitForFinalizerEvent (hEventFinalizer);
+#endif // !TARGET_WASM
-// Process pending finalizer work items from the GC first.
-FinalizerWorkItem* pWork = GCHeapUtilities::GetGCHeap()->GetExtraWorkForFinalization();
-while (pWork != NULL)
-{
-FinalizerWorkItem* pNext = pWork->next;
-pWork->callback(pWork);
-pWork = pNext;
-}
+ // Process pending finalizer work items from the GC first.
+ FinalizerWorkItem* pWork = GCHeapUtilities::GetGCHeap()->GetExtraWorkForFinalization();
+ while (pWork != NULL)
+ {
+ FinalizerWorkItem* pNext = pWork->next;
+ pWork->callback(pWork);
+ pWork = pNext;
+ }
+#ifndef TARGET_WASM
 #if defined(__linux__) && defined(FEATURE_EVENT_TRACE)
-if (g_TriggerHeapDump && (minipal_lowres_ticks() > (LastHeapDumpTime + LINUX_HEAP_DUMP_TIME_OUT)))
-{
-s_forcedGCInProgress = true;
-GetFinalizerThread()->DisablePreemptiveGC();
-GCHeapUtilities::GetGCHeap()->GarbageCollect(2, false, collection_blocking);
-GetFinalizerThread()->EnablePreemptiveGC();
-s_forcedGCInProgress = false;
+ if (g_TriggerHeapDump && (minipal_lowres_ticks() > (LastHeapDumpTime + LINUX_HEAP_DUMP_TIME_OUT)))
+ {
+ s_forcedGCInProgress = true;
+ GetFinalizerThread()->DisablePreemptiveGC();
+ GCHeapUtilities::GetGCHeap()->GarbageCollect(2, false, collection_blocking);
+ GetFinalizerThread()->EnablePreemptiveGC();
+ s_forcedGCInProgress = false;
-LastHeapDumpTime = minipal_lowres_ticks();
-g_TriggerHeapDump = FALSE;
-}
+ LastHeapDumpTime = minipal_lowres_ticks();
+ g_TriggerHeapDump = FALSE;
+ }
 #endif
- if (gcGenAnalysisState == GcGenAnalysisState::Done)
+ if (gcGenAnalysisState == GcGenAnalysisState::Done)
+ {
+ gcGenAnalysisState = GcGenAnalysisState::Disabled;
+ if (gcGenAnalysisTrace)
  {
- gcGenAnalysisState = GcGenAnalysisState::Disabled;
- if (gcGenAnalysisTrace)
- {
 #ifdef FEATURE_PERFTRACING
-EventPipeAdapter::Disable(gcGenAnalysisEventPipeSessionId);
+ EventPipeAdapter::Disable(gcGenAnalysisEventPipeSessionId);
 #ifdef GEN_ANALYSIS_STRESS
-GenAnalysis::EnableGenerationalAwareSession();
+ GenAnalysis::EnableGenerationalAwareSession();
 #endif //GEN_ANALYSIS_STRESS
 #endif //FEATURE_PERFTRACING
- }
- // Writing an empty file to indicate completion
- WCHAR outputPath[MAX_PATH];
- ReplacePid(GENAWARE_COMPLETION_FILE_NAME, outputPath, MAX_PATH);
- FILE* fp = NULL;
- if (fopen_lp(&fp, outputPath, W("w+")) == 0)
- {
- fclose(fp);
- }
- }
- if (!bPriorityBoosted)
- {
- if (GetFinalizerThread()->SetThreadPriority(THREAD_PRIORITY_HIGHEST))
- bPriorityBoosted = TRUE;
  }
- // The Finalizer thread is started very early in EE startup. We deferred
- // some initialization until a point we are sure the EE is up and running. At
- // this point we make a single attempt and if it fails won't try again.
- if (!s_InitializedFinalizerThreadForPlatform)
+ // Writing an empty file to indicate completion
+ WCHAR outputPath[MAX_PATH];
+ ReplacePid(GENAWARE_COMPLETION_FILE_NAME, outputPath, MAX_PATH);
+ FILE* fp = NULL;
+ if (fopen_lp(&fp, outputPath, W("w+")) == 0)
  {
- s_InitializedFinalizerThreadForPlatform = TRUE;
- Thread::InitializationForManagedThreadInNative(GetFinalizerThread());
+ fclose(fp);
  }
+ }
- JitHost::Reclaim();
+ if (!s_PriorityBoosted)
+ {
+ if (GetFinalizerThread()->SetThreadPriority(THREAD_PRIORITY_HIGHEST))
+ s_PriorityBoosted = true;
+ }
- GetFinalizerThread()->DisablePreemptiveGC();
+ // The Finalizer thread is started very early in EE startup. We deferred
+ // some initialization until a point we are sure the EE is up and running. At
+ // this point we make a single attempt and if it fails won't try again.
+ if (!s_InitializedFinalizerThreadForPlatform)
+ {
+ s_InitializedFinalizerThreadForPlatform = true;
+ Thread::InitializationForManagedThreadInNative(GetFinalizerThread());
+ }
+#endif // !TARGET_WASM
- // we might want to do some extra work on the finalizer thread
- // check and do it
- if (HaveExtraWorkForFinalizer())
- {
- DoExtraWorkForFinalizer(GetFinalizerThread());
- }
- LOG((LF_GC, LL_INFO100, "***** Calling Finalizers\n"));
+ JitHost::Reclaim();
- int observedFullGcCount =
- GCHeapUtilities::GetGCHeap()->CollectionCount(GCHeapUtilities::GetGCHeap()->GetMaxGeneration());
- FinalizeAllObjects();
+ GetFinalizerThread()->DisablePreemptiveGC();
-// Anyone waiting to drain the Q can now wake up. Note that there is a
-// race in that another thread starting a drain, as we leave a drain, may
- // consider itself satisfied by the drain that just completed.
- // Thus we include the Full GC count that we have certaily observed.
-SignalFinalizationDone(observedFullGcCount);
+ // we might want to do some extra work on the finalizer thread
+ // check and do it
+if (HaveExtraWorkForFinalizer())
+{
+DoExtraWorkForFinalizer(GetFinalizerThread());
  }
+ LOG((LF_GC, LL_INFO100, "***** Calling Finalizers\n"));
- if (s_InitializedFinalizerThreadForPlatform)
- Thread::CleanUpForManagedThreadInNative(GetFinalizerThread());
+ int observedFullGcCount =
+ GCHeapUtilities::GetGCHeap()->CollectionCount(GCHeapUtilities::GetGCHeap()->GetMaxGeneration());
+ FinalizeAllObjects();
+#ifndef TARGET_WASM
+ // Anyone waiting to drain the Q can now wake up. Note that there is a
+ // race in that another thread starting a drain, as we leave a drain, may
+ // consider itself satisfied by the drain that just completed.
+ // Thus we include the Full GC count that we have certaily observed.
+ SignalFinalizationDone(observedFullGcCount);
+#endif // !TARGET_WASM
 }
 DWORD WINAPI FinalizerThread::FinalizerThreadStart(void *args)
 {
+ CONTRACTL
+ {
+#ifdef TARGET_UNIX // because UNINSTALL_UNHANDLED_MANAGED_EXCEPTION_TRAP is catching exceptions only on Unix. On Windows OS is handling that.
+ NOTHROW;
+#else // TARGET_UNIX
+ THROWS;
+#endif // TARGET_UNIX
+ GC_TRIGGERS;
+ MODE_PREEMPTIVE;
+ }
+ CONTRACTL_END;
  ClrFlsSetThreadType (ThreadType_Finalizer);
  ASSERT(args == 0);
@@ Expand DownExpand Up / @@ -580,6 +649,7 @@ void FinalizerThread::FinalizerThreadCreate() @@
  MODE_ANY;
  } CONTRACTL_END;
+#ifndef TARGET_WASM
 #ifndef TARGET_UNIX
  MHandles[kLowMemoryNotification] =
  CreateMemoryResourceNotification(LowMemoryResourceNotification);
@@ Expand DownExpand Up / @@ -617,6 +687,10 @@ void FinalizerThread::FinalizerThreadCreate() @@
  // and the moment we execute the test below.
  _ASSERTE(dwRet == 1 || dwRet == 2);
  }
+#else // !TARGET_WASM
+ // capture the current (single) thread as the finalizer thread
+ g_pFinalizerThread = PTR_Thread(GetThread());
+#endif // !TARGET_WASM
 }
 static int g_fullGcCountSeenByFinalization;
@@ Expand Down @@

src/coreclr/vm/finalizerthread.h

-Original file line number
+Diff line change
@@ Expand Up / @@ -62,6 +62,9 @@ class FinalizerThread @@
  static void SignalFinalizationDone(int observedFullGcCount);
  static VOID FinalizerThreadWorker(void *args);
+ static VOID FinalizerThreadWorkerIteration(void *args);
  static DWORD WINAPI FinalizerThreadStart(void *args);
  static void FinalizerThreadCreate();
@@ Expand Down @@

src/libraries/Common/tests/System/Net/Http/ResponseStreamTest.cs

-Original file line number
+Diff line change
@@ Expand Up / @@ -392,6 +392,7 @@ public async Task BrowserHttpHandler_Streaming() @@
  }
  }
+ [ActiveIssue("https://github.com/dotnet/runtime/issues/123572", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser), nameof(PlatformDetection.IsCoreCLR))]
  [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsChromium))]
  public async Task BrowserHttpHandler_StreamingRequest()
  {
@@ Expand Down @@

src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs

-Original file line number
+Diff line change
@@ Expand Up @@
  // heavily on Reflection.Emit
  public static bool IsXmlDsigXsltTransformSupported => !PlatformDetection.IsInAppContainer && IsReflectionEmitSupported;
- public static bool IsPreciseGcSupported => !IsMonoRuntime
- && !IsBrowser; // TODO-WASM: https://github.com/dotnet/runtime/issues/114096
+ public static bool IsPreciseGcSupported => !IsMonoRuntime;
  public static bool IsRareEnumsSupported => !IsNativeAot;
@@ Expand Down @@

...raries/System.Runtime/tests/System.Threading.Tasks.Tests/Task/ExecutionContextFlowTest.cs

-Original file line number
+Diff line change
@@ Expand Up @@
  yield return new object[] { new Func<TaskCompletionSource<int>>(() => new TaskCompletionSource<int>(new object(), TaskCreationOptions.RunContinuationsAsynchronously)) };
  }
+ [ActiveIssue("https://github.com/dotnet/runtime/issues/114096", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser), nameof(PlatformDetection.IsCoreCLR))]
  [ConditionalTheory(typeof(PlatformDetection), nameof(PlatformDetection.IsPreciseGcSupported))]
  [MemberData(nameof(TaskCompletionSourceDoesntCaptureExecutionContext_MemberData))]
  public static async Task TaskCompletionSourceDoesntCaptureExecutionContext(Func<TaskCompletionSource<int>> tcsFactory)
@@ Expand Down @@

src/libraries/System.Threading/tests/ThreadLocalTests.cs

-Original file line number
+Diff line change
@@ Expand Up @@
  Assert.Throws<ObjectDisposedException>(() => values = tl.Values);
  }
+ [ActiveIssue("https://github.com/dotnet/runtime/issues/114096", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser), nameof(PlatformDetection.IsCoreCLR))]
  [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsPreciseGcSupported))]
  public static void RunThreadLocalTest8_Values_NegativeCases()
  {
@@ Expand Down @@

src/native/libs/Common/JavaScript/types/ems-ambient.ts

-Original file line number
+Diff line change
@@ Expand Up @@
  _GetDotNetRuntimeContractDescriptor: () => void;
  _SystemJS_ExecuteTimerCallback: () => void;
  _SystemJS_ExecuteBackgroundJobCallback: () => void;
+ _SystemJS_ExecuteFinalizationCallback: () => void;
  _BrowserHost_CreateHostContract: () => VoidPtr;
  _BrowserHost_InitializeCoreCLR: (propertiesCount: number, propertyKeys: CharPtrPtr, propertyValues: CharPtrPtr) => number;
  _BrowserHost_ExecuteAssembly: (mainAssemblyNamePtr: number, argsLength: number, argsPtr: number) => number;
@@ Expand Down @@

src/native/libs/System.Native.Browser/libSystem.Native.Browser.footer.js

-Original file line number
+Diff line change
@@ Expand Up / @@ -21,7 +21,9 @@ @@
  let commonDeps = [
  "$BROWSER_UTILS",
- "SystemJS_ExecuteTimerCallback", "SystemJS_ExecuteBackgroundJobCallback"
+ "SystemJS_ExecuteTimerCallback",
+ "SystemJS_ExecuteBackgroundJobCallback",
+ "SystemJS_ExecuteFinalizationCallback",
  ];
  const lib = {
  $DOTNET: {
@@ Expand Down @@

src/native/libs/System.Native.Browser/native/index.ts

-Original file line number
+Diff line change
@@ Expand Up / @@ -10,7 +10,7 @@ import GitHash from "consts:gitHash"; @@
 export { SystemJS_RandomBytes } from "./crypto";
 export { SystemJS_GetLocaleInfo } from "./globalization-locale";
 export { SystemJS_RejectMainPromise, SystemJS_ResolveMainPromise, SystemJS_ConsoleClear } from "./main";
-export { SystemJS_ScheduleTimer, SystemJS_ScheduleBackgroundJob } from "./scheduling";
+export { SystemJS_ScheduleTimer, SystemJS_ScheduleBackgroundJob, SystemJS_ScheduleFinalization } from "./scheduling";
 export const gitHash = GitHash;
 export function dotnetInitializeModule(internals: InternalExchange): void {
@@ Expand Down @@

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