8273482: Remove "foreground work" concept from WorkGang

Reviewed-by: tschatzl, kbarrett

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

@@ -34,17 +34,6 @@
 #include "runtime/semaphore.hpp"
 #include "runtime/thread.inline.hpp"
 
-static void run_foreground_task_if_needed(AbstractGangTask* task, uint num_workers,
-                                          bool add_foreground_work) {
-  if (add_foreground_work) {
-    log_develop_trace(gc, workgang)("Running work gang: %s task: %s worker: foreground",
-      Thread::current()->name(), task->name());
-    task->work(num_workers);
-    log_develop_trace(gc, workgang)("Finished work gang: %s task: %s worker: foreground "
-      "thread: " PTR_FORMAT, Thread::current()->name(), task->name(), p2i(Thread::current()));
-  }
-}
-
 // WorkGang dispatcher implemented with semaphores.
 //
 // Semaphores don't require the worker threads to re-claim the lock when they wake up.
@@ -79,7 +68,7 @@ public:
 
   // Distributes the task out to num_workers workers.
   // Returns when the task has been completed by all workers.
-  void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers, bool add_foreground_work) {
+  void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) {
     // No workers are allowed to read the state variables until they have been signaled.
     _task         = task;
     _not_finished = num_workers;
@@ -87,8 +76,6 @@ public:
     // Dispatch 'num_workers' number of tasks.
     _start_semaphore->signal(num_workers);
 
-    run_foreground_task_if_needed(task, num_workers, add_foreground_work);
-
     // Wait for the last worker to signal the coordinator.
     _end_semaphore->wait();
 
@@ -198,14 +185,14 @@ void WorkGang::run_task(AbstractGangTask* task) {
   run_task(task, active_workers());
 }
 
-void WorkGang::run_task(AbstractGangTask* task, uint num_workers, bool add_foreground_work) {
+void WorkGang::run_task(AbstractGangTask* task, uint num_workers) {
   guarantee(num_workers <= total_workers(),
             "Trying to execute task %s with %u workers which is more than the amount of total workers %u.",
             task->name(), num_workers, total_workers());
   guarantee(num_workers > 0, "Trying to execute task %s with zero workers", task->name());
   uint old_num_workers = _active_workers;
   update_active_workers(num_workers);
-  _dispatcher->coordinator_execute_on_workers(task, num_workers, add_foreground_work);
+  _dispatcher->coordinator_execute_on_workers(task, num_workers);
   update_active_workers(old_num_workers);
 }
 

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

@@ -167,9 +167,8 @@ class WorkGang : public CHeapObj<mtInternal> {
   // Run a task with the given number of workers, returns
   // when the task is done. The number of workers must be at most the number of
   // active workers.  Additional workers may be created if an insufficient
-  // number currently exists. If the add_foreground_work flag is true, the current thread
-  // is used to run the task too.
-  void run_task(AbstractGangTask* task, uint num_workers, bool add_foreground_work = false);
+  // number currently exists.
+  void run_task(AbstractGangTask* task, uint num_workers);
 };
 
 // Temporarily try to set the number of active workers.

src/hotspot/share/gc/shenandoah/shenandoahCodeRoots.cpp

@@ -355,7 +355,6 @@ ShenandoahCodeRootsIterator::ShenandoahCodeRootsIterator() :
         _par_iterator(CodeCache::heaps()),
         _table_snapshot(NULL) {
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
-  assert(!Thread::current()->is_Worker_thread(), "Should not be acquired by workers");
   CodeCache_lock->lock_without_safepoint_check();
   _table_snapshot = ShenandoahCodeRoots::table()->snapshot_for_iteration();
 }

src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.cpp

@@ -258,7 +258,6 @@ ShenandoahHeapIterationRootScanner::ShenandoahHeapIterationRootScanner() :
  }
 
  void ShenandoahHeapIterationRootScanner::roots_do(OopClosure* oops) {
-   assert(Thread::current()->is_VM_thread(), "Only by VM thread");
    // Must use _claim_none to avoid interfering with concurrent CLDG iteration
    CLDToOopClosure clds(oops, ClassLoaderData::_claim_none);
    MarkingCodeBlobClosure code(oops, !CodeBlobToOopClosure::FixRelocations);

src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.inline.hpp

@@ -86,9 +86,8 @@ ShenandoahClassLoaderDataRoots<CONCURRENT, SINGLE_THREADED>::ShenandoahClassLoad
     ClassLoaderDataGraph_lock->lock();
   }
 
-  // Non-concurrent mode only runs at safepoints by VM thread
+  // Non-concurrent mode only runs at safepoints
   assert(CONCURRENT || SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
-  assert(CONCURRENT || Thread::current()->is_VM_thread(), "Can only be done by VM thread");
 }
 
 template <bool CONCURRENT, bool SINGLE_THREADED>

src/hotspot/share/services/heapDumper.cpp

@@ -1771,7 +1771,7 @@ void VM_HeapDumper::doit() {
   if (gang == NULL) {
     work(0);
   } else {
-    gang->run_task(this, gang->active_workers(), true);
+    gang->run_task(this);
   }
 
   // Now we clear the global variables, so that a future dumper can run.
@@ -1780,7 +1780,7 @@ void VM_HeapDumper::doit() {
 }
 
 void VM_HeapDumper::work(uint worker_id) {
-  if (!Thread::current()->is_VM_thread()) {
+  if (worker_id != 0) {
     writer()->writer_loop();
     return;
   }