[K/N] Simplify safepoint slowpath in CMS

^KT-50291

Merge-request: KT-MR-5263

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

@@ -57,8 +57,6 @@ struct SweepTraits {
     }
 };
 
-// Global, because it's accessed on a hot path: avoid memory load from `this`.
-std::atomic<bool> gNeedSafepointSlowpath = false;
 } // namespace
 
 ALWAYS_INLINE void gc::ConcurrentMarkAndSweep::ThreadData::SafePointFunctionPrologue() noexcept {
@@ -71,9 +69,7 @@ ALWAYS_INLINE void gc::ConcurrentMarkAndSweep::ThreadData::SafePointLoopBody() n
 
 void gc::ConcurrentMarkAndSweep::ThreadData::SafePointAllocation(size_t size) noexcept {
     threadData_.gcScheduler().OnSafePointAllocation(size);
-    if (gNeedSafepointSlowpath.load()) {
+    mm::SuspendIfRequested();
-        SafePointSlowPath();
-    }
 }
 void gc::ConcurrentMarkAndSweep::ThreadData::ScheduleAndWaitFullGC() noexcept {
     ThreadStateGuard guard(ThreadState::kNative);
@@ -98,13 +94,7 @@ void gc::ConcurrentMarkAndSweep::ThreadData::OnOOM(size_t size) noexcept {
 
 ALWAYS_INLINE void gc::ConcurrentMarkAndSweep::ThreadData::SafePointRegular(size_t weight) noexcept {
     threadData_.gcScheduler().OnSafePointRegular(weight);
-    if (gNeedSafepointSlowpath.load()) {
+    mm::SuspendIfRequested();
-        SafePointSlowPath();
-    }
-}
-
-NO_EXTERNAL_CALLS_CHECK NO_INLINE void gc::ConcurrentMarkAndSweep::ThreadData::SafePointSlowPath() noexcept {
-    threadData_.suspensionData().suspendIfRequested();
 }
 
 gc::ConcurrentMarkAndSweep::ConcurrentMarkAndSweep() noexcept :
@@ -131,22 +121,11 @@ gc::ConcurrentMarkAndSweep::~ConcurrentMarkAndSweep() {
     gcThread_.join();
 }
 
-
-void gc::ConcurrentMarkAndSweep::RequestThreadsSuspension() noexcept {
-    gNeedSafepointSlowpath = true;
-    bool didSuspend = mm::RequestThreadsSuspension();
-    RuntimeAssert(didSuspend, "Only GC thread can request suspension");
-}
-
-void gc::ConcurrentMarkAndSweep::ResumeThreads() noexcept {
-    mm::ResumeThreads();
-    gNeedSafepointSlowpath = false;
-}
-
 bool gc::ConcurrentMarkAndSweep::PerformFullGC(int64_t epoch) noexcept {
     RuntimeLogDebug({kTagGC}, "Attempt to suspend threads by thread %d", konan::currentThreadId());
     auto timeStartUs = konan::getTimeMicros();
-    RequestThreadsSuspension();
+    bool didSuspend = mm::RequestThreadsSuspension();
+    RuntimeAssert(didSuspend, "Only GC thread can request suspension");
     RuntimeLogDebug({kTagGC}, "Requested thread suspension by thread %d", konan::currentThreadId());
 
     RuntimeAssert(!kotlin::mm::IsCurrentThreadRegistered(), "Concurrent GC must run on unregistered thread");
@@ -179,7 +158,7 @@ bool gc::ConcurrentMarkAndSweep::PerformFullGC(int64_t epoch) noexcept {
 
     auto objectFactoryIterable = mm::GlobalData::Instance().objectFactory().LockForIter();
 
-    ResumeThreads();
+    mm::ResumeThreads();
     auto timeResumeUs = konan::getTimeMicros();
 
     RuntimeLogDebug({kTagGC},

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

@@ -67,7 +67,6 @@ public:
 
     private:
         void SafePointRegular(size_t weight) noexcept;
-        void SafePointSlowPath() noexcept;
 
         ConcurrentMarkAndSweep& gc_;
         mm::ThreadData& threadData_;
@@ -81,8 +80,6 @@ public:
 private:
     // Returns `true` if GC has happened, and `false` if not (because someone else has suspended the threads).
     bool PerformFullGC(int64_t epoch) noexcept;
-    void RequestThreadsSuspension() noexcept;
-    void ResumeThreads() noexcept;
 
     uint64_t lastGCTimestampUs_ = 0;
     GCStateHolder state_;

kotlin-native/runtime/src/mm/cpp/ThreadSuspension.cpp

@@ -86,6 +86,12 @@ void kotlin::mm::WaitForThreadsSuspension() noexcept {
     }
 }
 
+ALWAYS_INLINE void kotlin::mm::SuspendIfRequested() noexcept {
+    if (IsThreadSuspensionRequested()) {
+        mm::ThreadRegistry::Instance().CurrentThreadData()->suspensionData().suspendIfRequestedSlowPath();
+    }
+}
+
 void kotlin::mm::ResumeThreads() noexcept {
     // From the std::condition_variable docs:
     // Even if the shared variable is atomic, it must be modified under

kotlin-native/runtime/src/mm/cpp/ThreadSuspension.hpp

@@ -49,6 +49,8 @@ public:
     }
 
 private:
+    friend void SuspendIfRequested() noexcept;
+
     std::atomic<ThreadState> state_;
     std::atomic<bool> suspended_;
     void suspendIfRequestedSlowPath() noexcept;
@@ -56,6 +58,7 @@ private:
 
 bool RequestThreadsSuspension() noexcept;
 void WaitForThreadsSuspension() noexcept;
+void SuspendIfRequested() noexcept;
 
 /**
  * Suspends all threads registered in ThreadRegistry except threads that are in the Native state.