commit 859095b60accb9e7e6f8881cb1e75227d366e73e
author Alexander Shabalin <alexander.shabalin@jetbrains.com> Thu Sep 04 12:47:47 2025 +0200
committer Alexander Shabalin <alexander.shabalin@jetbrains.com> Thu Sep 04 12:54:44 2025 +0200
tree 8f68a3e61f16a79a788e368da94559c46e41ef87
parent e314e787103f887084252ef9e43cb6258db6bfdb

[K/N] In CMS add a maximum number of iterations for queue flushing

^KT-79384

kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.cpp

diff --git a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.cpp b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.cpp
index a81e641..820866c 100644
--- a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.cpp
+++ b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.cpp
@@ -145,7 +145,8 @@
     std::unique_lock markTerminationGuard(markTerminationMutex_);
 
     // has to happen under the termination lock guard
-    flushMutatorQueues();
+    if (!flushMutatorQueues())
+        return false;
 
     // After the mutators have been forced to flush their local queues,
     // there is only on possibility for this counter to remain the same as on a previous iteration:
@@ -164,15 +165,18 @@
     return true;
 }
 
-void gc::mark::ConcurrentMark::flushMutatorQueues() noexcept {
+bool gc::mark::ConcurrentMark::flushMutatorQueues() noexcept {
     for (auto& mutator : *lockedMutatorsList_) {
         mutator.gc().impl().mark_.flushAction_.construct();
     }
 
+    bool success = false;
     {
         FlushActionActivator flushActivator{};
 
         // wait all mutators flushed
+        // TODO: How many iterations are actually needed?
+        size_t iterationCountLeft = 1000;
         while (true) {
             bool allDone = true;
             for (auto& mutator : *lockedMutatorsList_) {
@@ -183,7 +187,12 @@
                     allDone = false;
                 }
             }
-            if (allDone) break;
+            if (allDone) {
+                success = true;
+                break;
+            }
+            if (--iterationCountLeft == 0)
+                break;
             std::this_thread::yield();
         }
     }
@@ -192,6 +201,7 @@
     for (auto& mutator : *lockedMutatorsList_) {
         mutator.gc().impl().mark_.flushAction_.destroy();
     }
+    return success;
 }
 
 void gc::mark::ConcurrentMark::resetMutatorFlags() {

kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.hpp

diff --git a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.hpp b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.hpp
index 3c82481..48f1bde 100644
--- a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.hpp
+++ b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMark.hpp
@@ -147,7 +147,7 @@
     void completeMutatorsRootSet(MarkTraits::MarkQueue& markQueue);
     void tryCollectRootSet(mm::ThreadData& thread, ParallelProcessor::Worker& markQueue);
     bool tryTerminateMark(std::size_t& everSharedBatches) noexcept;
-    void flushMutatorQueues() noexcept;
+    bool flushMutatorQueues() noexcept;
     void endMarkingEpoch();
 
     void resetMutatorFlags();