8251570: JDK-8215624 causes assert(worker_id < _n_workers) failed: In…

…valid worker_id

Reviewed-by: rschmelter, clanger
Backport-of: 2631422

src/hotspot/share/gc/cms/cmsHeap.hpp

@@ -67,9 +67,6 @@ class CMSHeap : public GenCollectedHeap {
 
   virtual void print_gc_threads_on(outputStream* st) const;
   virtual void gc_threads_do(ThreadClosure* tc) const;
-  // Runs the given AbstractGangTask with the current active workers.
-  // No workGang for CmsHeap, work serially with thread 0
-  virtual void run_task(AbstractGangTask* task) { task->work(0); }
   virtual void print_on_error(outputStream* st) const;
 
   // Perform a full collection of the heap; intended for use in implementing

src/hotspot/share/gc/epsilon/epsilonHeap.hpp

@@ -136,10 +136,6 @@ class EpsilonHeap : public CollectedHeap {
   virtual void print_gc_threads_on(outputStream* st) const {}
   virtual void gc_threads_do(ThreadClosure* tc) const {}
 
-  // Runs the given AbstractGangTask with the current active workers
-  // No workGang for EpsilonHeap, work serially with thread 0
-  virtual void run_task(AbstractGangTask* task) { task->work(0); }
-
   // No heap verification
   virtual void prepare_for_verify() {}
   virtual void verify(VerifyOption option) {}

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -153,10 +153,6 @@ void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_region
   reset_from_card_cache(start_idx, num_regions);
 }
 
-void G1CollectedHeap::run_task(AbstractGangTask* task) {
-   workers()->run_task(task, workers()->active_workers());
-}
-
 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
                                              MemRegion mr) {
   return new HeapRegion(hrs_index, bot(), mr);

src/hotspot/share/gc/g1/g1CollectedHeap.hpp

@@ -528,9 +528,6 @@ class G1CollectedHeap : public CollectedHeap {
 
   WorkGang* workers() const { return _workers; }
 
-  // Runs the given AbstractGangTask with the current active workers.
-  virtual void run_task(AbstractGangTask* task);
-
   G1Allocator* allocator() {
     return _allocator;
   }

src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp

@@ -604,12 +604,6 @@ void ParallelScavengeHeap::print_gc_threads_on(outputStream* st) const {
   PSScavenge::gc_task_manager()->print_threads_on(st);
 }
 
-void ParallelScavengeHeap::run_task(AbstractGangTask* task) {
-  WorkGang workers("GC Threads", ParallelGCThreads, true, false);
-  workers.initialize_workers();
-  workers.run_task(task);
-}
-
 void ParallelScavengeHeap::print_tracing_info() const {
   AdaptiveSizePolicyOutput::print();
   log_debug(gc, heap, exit)("Accumulated young generation GC time %3.7f secs", PSScavenge::accumulated_time()->seconds());

src/hotspot/share/gc/parallel/parallelScavengeHeap.hpp

@@ -231,8 +231,6 @@ class ParallelScavengeHeap : public CollectedHeap {
   virtual void print_on_error(outputStream* st) const;
   virtual void print_gc_threads_on(outputStream* st) const;
   virtual void gc_threads_do(ThreadClosure* tc) const;
-  // Runs the given AbstractGangTask with the current active workers.
-  virtual void run_task(AbstractGangTask* task);
   virtual void print_tracing_info() const;
 
   void verify(VerifyOption option /* ignored */);

src/hotspot/share/gc/serial/serialHeap.hpp

@@ -82,9 +82,6 @@ class SerialHeap : public GenCollectedHeap {
   void oop_since_save_marks_iterate(OopClosureType1* cur,
                                     OopClosureType2* older);
 
-  // Runs the given AbstractGangTask with the current active workers.
-  // No workGang for SerialHeap, work serially with thread 0.
-  virtual void run_task(AbstractGangTask* task) { task->work(0); }
 };
 
 #endif // SHARE_VM_GC_CMS_CMSHEAP_HPP

src/hotspot/share/gc/shared/collectedHeap.hpp

@@ -528,9 +528,6 @@ class CollectedHeap : public CHeapObj<mtInternal> {
   // Iterator for all GC threads (other than VM thread)
   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 
-  // Run given task. Possibly in parallel if the GC supports it.
-  virtual void run_task(AbstractGangTask* task) = 0;
-
   // Print any relevant tracing info that flags imply.
   // Default implementation does nothing.
   virtual void print_tracing_info() const = 0;

src/hotspot/share/gc/shared/workgroup.hpp

@@ -199,6 +199,27 @@ class AbstractWorkGang : public CHeapObj<mtInternal> {
   virtual AbstractGangWorker* allocate_worker(uint which) = 0;
 };
 
+// Temporarily try to set the number of active workers.
+// It's not guaranteed that it succeeds, and users need to
+// query the number of active workers.
+class WithUpdatedActiveWorkers : public StackObj {
+private:
+  AbstractWorkGang* const _gang;
+  const uint              _old_active_workers;
+
+public:
+  WithUpdatedActiveWorkers(AbstractWorkGang* gang, uint requested_num_workers) :
+      _gang(gang),
+      _old_active_workers(gang->active_workers()) {
+    uint capped_num_workers = MIN2(requested_num_workers, gang->total_workers());
+    gang->update_active_workers(capped_num_workers);
+  }
+
+  ~WithUpdatedActiveWorkers() {
+    _gang->update_active_workers(_old_active_workers);
+  }
+};
+
 // An class representing a gang of workers.
 class WorkGang: public AbstractWorkGang {
   // To get access to the GangTaskDispatcher instance.

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -206,10 +206,6 @@ class ShenandoahHeap : public CollectedHeap {
 
   void gc_threads_do(ThreadClosure* tcl) const;
 
-  // Runs the given AbstractGangTask with the current active workers
-  // No workGang for shenandoahHeap, work serially with thread 0
-  virtual void run_task(AbstractGangTask* task) { task->work(0); }
-
 // ---------- Heap regions handling machinery
 //
 private:

src/hotspot/share/gc/z/zCollectedHeap.hpp

@@ -103,10 +103,6 @@ class ZCollectedHeap : public CollectedHeap {
   virtual void object_iterate(ObjectClosure* cl);
   virtual void safe_object_iterate(ObjectClosure* cl);
 
-  // Runs the given AbstractGangTask with the current active workers.
-  // No workGang for zHeap, work serially with thread 0
-  virtual void run_task(AbstractGangTask* task) { task->work(0); }
-
   virtual HeapWord* block_start(const void* addr) const;
   virtual size_t block_size(const HeapWord* addr) const;
   virtual bool block_is_obj(const HeapWord* addr) const;

src/hotspot/share/memory/heapInspection.cpp

@@ -780,13 +780,25 @@ uintx HeapInspection::populate_table(KlassInfoTable* cit, BoolObjectClosure *fil
   // Try parallel first.
   if (parallel_thread_num > 1) {
     ResourceMark rm;
-    ParallelObjectIterator* poi = Universe::heap()->parallel_object_iterator(parallel_thread_num);
-    if (poi != NULL) {
-      ParHeapInspectTask task(poi, cit, filter);
-      Universe::heap()->run_task(&task);
-      delete poi;
-      if (task.success()) {
-        return task.missed_count();
+    WorkGang* gang = Universe::heap()->get_safepoint_workers();
+    if (gang != NULL) {
+      // The GC provided a WorkGang to be used during a safepoint.
+
+      // Can't run with more threads than provided by the WorkGang.
+      WithUpdatedActiveWorkers update_and_restore(gang, parallel_thread_num);
+
+      ParallelObjectIterator* poi = Universe::heap()->parallel_object_iterator(gang->active_workers());
+      if (poi != NULL) {
+        // The GC supports parallel object iteration.
+
+        ParHeapInspectTask task(poi, cit, filter);
+        // Run task with the active workers.
+        gang->run_task(&task);
+
+        delete poi;
+        if (task.success()) {
+          return task.missed_count();
+        }
       }
     }
   }