Merge pull request #5131 from amicic/collector_stw_flag

gc/base/Collector.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 1991, 2016 IBM Corp. and others
+ * Copyright (c) 1991, 2020 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -202,6 +202,8 @@ MM_Collector::preCollect(MM_EnvironmentBase* env, MM_MemorySubSpace* subSpace, M
 	 */
 	completeExternalConcurrentCycle(env);
 
+	_stwCollectionInProgress = true;
+
 	/* Record the master GC thread CPU time at the start to diff later */
 	_masterThreadCpuTimeStart = omrthread_get_self_cpu_time(env->getOmrVMThread()->_os_thread);
 
@@ -461,6 +463,9 @@ MM_Collector::postCollect(MM_EnvironmentBase* env, MM_MemorySubSpace* subSpace)
 		/* Set the excessive GC state, whether it was an implicit or system GC */
 		setThreadFailAllocFlag(env, excessiveGCDetected);
 	}
+
+	Assert_MM_true(_stwCollectionInProgress);
+	_stwCollectionInProgress = false;
 }
 
 /**

gc/base/Collector.hpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * (c) Copyright 1991, 2018 IBM Corp. and others
+ * (c) Copyright 1991, 2020 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -60,6 +60,7 @@ class MM_Collector : public MM_BaseVirtual
 	bool _gcCompleted;
 	bool _isRecursiveGC;
 	bool _disableGC;
+	bool _stwCollectionInProgress;  /**< if set, the whole or partial STW phase is in progress (mutators not running) */
 
 	uintptr_t _collectorExpandedSize;
 	uintptr_t _cycleType;
@@ -90,6 +91,15 @@ class MM_Collector : public MM_BaseVirtual
 	 * @return boolean indicating if the last GC completed successfully.
 	 */
 	bool gcCompleted() { return _gcCompleted; }
+
+	/*
+	 * Return value of _stwCollectionInProgress flag
+	 */
+	bool isStwCollectionInProgress()
+	{
+		return _stwCollectionInProgress;
+	}
+
 
 private:
 	void setThreadFailAllocFlag(MM_EnvironmentBase *env, bool flag);
@@ -305,6 +315,7 @@ class MM_Collector : public MM_BaseVirtual
 		, _gcCompleted(false)
 		, _isRecursiveGC(false)
 		, _disableGC(false)
+		, _stwCollectionInProgress(false)
 		, _collectorExpandedSize(0)
 		, _cycleType(OMR_GC_CYCLE_TYPE_DEFAULT)
 		, _masterThreadCpuTimeStart(0)

gc/base/GlobalCollector.hpp

@@ -65,11 +65,6 @@ class MM_GlobalCollector : public MM_Collector {
 	}
 
 	virtual void yield(MM_EnvironmentBase *env) {};
-
-	virtual bool isStwCollectionInProgress()
-	{
-		return false;
-	}
 
 	/**
  	 * Perform any collector-specific initialization.

gc/base/standard/ConcurrentGC.cpp

@@ -1294,7 +1294,7 @@ MM_ConcurrentGC::tuneToHeap(MM_EnvironmentBase *env)
 	 */
 	if(0 == heapSize) {
 		Trc_MM_ConcurrentGC_tuneToHeap_Exit1(env->getLanguageVMThread());
-		assume0(!_stwCollectionInProgress);
+		Assert_MM_true(!_stwCollectionInProgress);
 		return;
 	}
 
@@ -2922,11 +2922,7 @@ MM_ConcurrentGC::internalPreCollect(MM_EnvironmentBase *env, MM_MemorySubSpace *
 
 	/* Ensure caller acquired exclusive VM access before calling */
 	Assert_MM_mustHaveExclusiveVMAccess(env->getOmrVMThread());
-
-	/* Set flag to show STW collector is active; some operations need to know if they
-	 * are called during a global collect or not, eg heapAddRange
-	 */
-	_stwCollectionInProgress = true;
+	Assert_MM_true(_stwCollectionInProgress);
 
 	/* Assume for now we will need to initialize the mark map. If we subsequenly find
 	 * we got far enough through the concurrent mark cycle then we will reset this flag
@@ -3155,7 +3151,6 @@ MM_ConcurrentGC::internalPostCollect(MM_EnvironmentBase *env, MM_MemorySubSpace
 	}
 
 	/* Collection is complete so reset flags */
-	_stwCollectionInProgress = false;
 	_forcedKickoff  = false;
 	_stats.clearKickoffReason();
 
@@ -3325,7 +3320,7 @@ MM_ConcurrentGC::heapReconfigured(MM_EnvironmentBase *env, HeapReconfigReason re
 	 *
 	 *  It is necessary that _rebuildInitWorkForAdd is set when we're here during an expand (after heapAddRange), or
 	 *  _rebuildInitWorkForRemove in the case of contract. However, it is not a sufficient check to ensure the reason we're
-	 *  here. For instance, when Concurent is on, _rebuildInitWorkForAdd will be set but not cleared.
+	 *  here. For instance, when Concurrent is on, _rebuildInitWorkForAdd will be set but not cleared.
 	 *  As a result, we can have multiple calls of expands interleaved with contracts, resulting in both flags being set.
 	 *  Similarly, we can end up here after scavenger tilt with any of the flags set.
 	 */

gc/base/standard/ConcurrentGC.hpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 1991, 2018 IBM Corp. and others
+ * Copyright (c) 1991, 2020 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -200,7 +200,6 @@ class MM_ConcurrentGC : public MM_ParallelGlobalGC
 	volatile uint32_t _conHelpersShutdownCount;
 	omrthread_monitor_t _conHelpersActivationMonitor;
 
-	bool _stwCollectionInProgress;  /**< if set, the final STW phase is in progress (mutators not running) */
 	bool _initializeMarkMap;
 	omrthread_monitor_t _initWorkMonitor;
 	omrthread_monitor_t _initWorkCompleteMonitor;
@@ -460,14 +459,6 @@ class MM_ConcurrentGC : public MM_ParallelGlobalGC
 		}	
 	}
 
-	/*
-	 * Return value of _stwCollectionInProgress flag
-	 */
-	virtual bool isStwCollectionInProgress()
-	{
-		return _stwCollectionInProgress;
-	}
-
 	/**
 	 * Return reference to Card Table
 	 */
@@ -494,7 +485,6 @@ class MM_ConcurrentGC : public MM_ParallelGlobalGC
 		,_conHelpersStarted(0)
 		,_conHelpersShutdownCount(0)
 		,_conHelpersActivationMonitor(NULL)
-		,_stwCollectionInProgress(false)
 		,_initializeMarkMap(false)
 		,_initWorkMonitor(NULL)
 		,_initWorkCompleteMonitor(NULL)