8032379: Remove the is_scavenging flag to process_strong_roots

Summary: Refactor the strong root processing to avoid using a boolean in addition to the ScanOption enum.
Reviewed-by: stefank, tschatzl, ehelin, jmasa

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp

@@ -3038,7 +3038,6 @@ void CMSCollector::verify_after_remark_work_1() {
   gch->gen_process_strong_roots(_cmsGen->level(),
                                 true,   // younger gens are roots
                                 true,   // activate StrongRootsScope
-                                false,  // not scavenging
                                 SharedHeap::ScanningOption(roots_scanning_options()),
                                 &notOlder,
                                 true,   // walk code active on stacks
@@ -3106,7 +3105,6 @@ void CMSCollector::verify_after_remark_work_2() {
   gch->gen_process_strong_roots(_cmsGen->level(),
                                 true,   // younger gens are roots
                                 true,   // activate StrongRootsScope
-                                false,  // not scavenging
                                 SharedHeap::ScanningOption(roots_scanning_options()),
                                 &notOlder,
                                 true,   // walk code active on stacks
@@ -3308,7 +3306,7 @@ bool ConcurrentMarkSweepGeneration::is_too_full() const {
 void CMSCollector::setup_cms_unloading_and_verification_state() {
   const  bool should_verify =   VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC
                              || VerifyBeforeExit;
-  const  int  rso           =   SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
+  const  int  rso           =   SharedHeap::SO_Strings | SharedHeap::SO_AllCodeCache;
 
   // We set the proper root for this CMS cycle here.
   if (should_unload_classes()) {   // Should unload classes this cycle
@@ -3744,10 +3742,9 @@ void CMSCollector::checkpointRootsInitialWork(bool asynch) {
       gch->gen_process_strong_roots(_cmsGen->level(),
                                     true,   // younger gens are roots
                                     true,   // activate StrongRootsScope
-                                    false,  // not scavenging
                                     SharedHeap::ScanningOption(roots_scanning_options()),
                                     &notOlder,
-                                    true,   // walk all of code cache if (so & SO_CodeCache)
+                                    true,   // walk all of code cache if (so & SO_AllCodeCache)
                                     NULL,
                                     &klass_closure);
     }
@@ -5244,14 +5241,13 @@ void CMSParInitialMarkTask::work(uint worker_id) {
   gch->gen_process_strong_roots(_collector->_cmsGen->level(),
                                 false,     // yg was scanned above
                                 false,     // this is parallel code
-                                false,     // not scavenging
                                 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()),
                                 &par_mri_cl,
-                                true,   // walk all of code cache if (so & SO_CodeCache)
+                                true,   // walk all of code cache if (so & SO_AllCodeCache)
                                 NULL,
                                 &klass_closure);
   assert(_collector->should_unload_classes()
-         || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache),
+         || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_AllCodeCache),
          "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops");
   _timer.stop();
   if (PrintCMSStatistics != 0) {
@@ -5381,14 +5377,13 @@ void CMSParRemarkTask::work(uint worker_id) {
   gch->gen_process_strong_roots(_collector->_cmsGen->level(),
                                 false,     // yg was scanned above
                                 false,     // this is parallel code
-                                false,     // not scavenging
                                 SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()),
                                 &par_mrias_cl,
-                                true,   // walk all of code cache if (so & SO_CodeCache)
+                                true,   // walk all of code cache if (so & SO_AllCodeCache)
                                 NULL,
                                 NULL);     // The dirty klasses will be handled below
   assert(_collector->should_unload_classes()
-         || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_CodeCache),
+         || (_collector->CMSCollector::roots_scanning_options() & SharedHeap::SO_AllCodeCache),
          "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops");
   _timer.stop();
   if (PrintCMSStatistics != 0) {
@@ -5972,7 +5967,6 @@ void CMSCollector::do_remark_non_parallel() {
     gch->gen_process_strong_roots(_cmsGen->level(),
                                   true,  // younger gens as roots
                                   false, // use the local StrongRootsScope
-                                  false, // not scavenging
                                   SharedHeap::ScanningOption(roots_scanning_options()),
                                   &mrias_cl,
                                   true,   // walk code active on stacks
@@ -5980,7 +5974,7 @@ void CMSCollector::do_remark_non_parallel() {
                                   NULL);  // The dirty klasses will be handled below
 
     assert(should_unload_classes()
-           || (roots_scanning_options() & SharedHeap::SO_CodeCache),
+           || (roots_scanning_options() & SharedHeap::SO_AllCodeCache),
            "if we didn't scan the code cache, we have to be ready to drop nmethods with expired weak oops");
   }
 

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -3396,14 +3396,12 @@ void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
 
     // We apply the relevant closures to all the oops in the
     // system dictionary, the string table and the code cache.
-    const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
+    const int so = SO_AllClasses | SO_Strings | SO_AllCodeCache;
 
     // Need cleared claim bits for the strong roots processing
     ClassLoaderDataGraph::clear_claimed_marks();
 
     process_strong_roots(true,      // activate StrongRootsScope
-                         false,     // we set "is scavenging" to false,
-                                    // so we don't reset the dirty cards.
                          ScanningOption(so),  // roots scanning options
                          &rootsCl,
                          &blobsCl,
@@ -4867,13 +4865,13 @@ g1_process_strong_roots(bool is_scavenging,
 
   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
 
-  assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow");
+  assert(so & SO_AllCodeCache || scan_rs != NULL, "must scan code roots somehow");
   // Walk the code cache/strong code roots w/o buffering, because StarTask
   // cannot handle unaligned oop locations.
   CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
 
   process_strong_roots(false, // no scoping; this is parallel code
-                       is_scavenging, so,
+                       so,
                        &buf_scan_non_heap_roots,
                        &eager_scan_code_roots,
                        scan_klasses
@@ -4921,7 +4919,7 @@ g1_process_strong_roots(bool is_scavenging,
   // the collection set.
   // Note all threads participate in this set of root tasks.
   double mark_strong_code_roots_ms = 0.0;
-  if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) {
+  if (g1_policy()->during_initial_mark_pause() && !(so & SO_AllCodeCache)) {
     double mark_strong_roots_start = os::elapsedTime();
     mark_strong_code_roots(worker_i);
     mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;

src/share/vm/gc_implementation/g1/g1MarkSweep.cpp

@@ -132,7 +132,6 @@ void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
   ClassLoaderDataGraph::clear_claimed_marks();
 
   sh->process_strong_roots(true,  // activate StrongRootsScope
-                           false, // not scavenging.
                            SharedHeap::SO_SystemClasses,
                            &GenMarkSweep::follow_root_closure,
                            &GenMarkSweep::follow_code_root_closure,
@@ -309,7 +308,6 @@ void G1MarkSweep::mark_sweep_phase3() {
   ClassLoaderDataGraph::clear_claimed_marks();
 
   sh->process_strong_roots(true,  // activate StrongRootsScope
-                           false, // not scavenging.
                            SharedHeap::SO_AllClasses,
                            &GenMarkSweep::adjust_pointer_closure,
                            NULL,  // do not touch code cache here

src/share/vm/gc_implementation/parNew/parNewGeneration.cpp

@@ -614,14 +614,13 @@ void ParNewGenTask::work(uint worker_id) {
   KlassScanClosure klass_scan_closure(&par_scan_state.to_space_root_closure(),
                                       gch->rem_set()->klass_rem_set());
 
-  int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
+  int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_ScavengeCodeCache;
 
   par_scan_state.start_strong_roots();
   gch->gen_process_strong_roots(_gen->level(),
                                 true,  // Process younger gens, if any,
                                        // as strong roots.
                                 false, // no scope; this is parallel code
-                                true,  // is scavenging
                                 SharedHeap::ScanningOption(so),
                                 &par_scan_state.to_space_root_closure(),
                                 true,   // walk *all* scavengable nmethods

src/share/vm/memory/defNewGeneration.cpp

@@ -622,13 +622,12 @@ void DefNewGeneration::collect(bool   full,
   assert(gch->no_allocs_since_save_marks(0),
          "save marks have not been newly set.");
 
-  int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
+  int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_ScavengeCodeCache;
 
   gch->gen_process_strong_roots(_level,
                                 true,  // Process younger gens, if any,
                                        // as strong roots.
                                 true,  // activate StrongRootsScope
-                                true,  // is scavenging
                                 SharedHeap::ScanningOption(so),
                                 &fsc_with_no_gc_barrier,
                                 true,   // walk *all* scavengable nmethods

src/share/vm/memory/genCollectedHeap.cpp

@@ -597,7 +597,6 @@ void GenCollectedHeap::
 gen_process_strong_roots(int level,
                          bool younger_gens_as_roots,
                          bool activate_scope,
-                         bool is_scavenging,
                          SharedHeap::ScanningOption so,
                          OopsInGenClosure* not_older_gens,
                          bool do_code_roots,
@@ -606,12 +605,12 @@ gen_process_strong_roots(int level,
   // General strong roots.
 
   if (!do_code_roots) {
-    SharedHeap::process_strong_roots(activate_scope, is_scavenging, so,
+    SharedHeap::process_strong_roots(activate_scope, so,
                                      not_older_gens, NULL, klass_closure);
   } else {
     bool do_code_marking = (activate_scope || nmethod::oops_do_marking_is_active());
     CodeBlobToOopClosure code_roots(not_older_gens, /*do_marking=*/ do_code_marking);
-    SharedHeap::process_strong_roots(activate_scope, is_scavenging, so,
+    SharedHeap::process_strong_roots(activate_scope, so,
                                      not_older_gens, &code_roots, klass_closure);
   }
 

src/share/vm/memory/genCollectedHeap.hpp

@@ -420,7 +420,6 @@ public:
                                 // The remaining arguments are in an order
                                 // consistent with SharedHeap::process_strong_roots:
                                 bool activate_scope,
-                                bool is_scavenging,
                                 SharedHeap::ScanningOption so,
                                 OopsInGenClosure* not_older_gens,
                                 bool do_code_roots,

src/share/vm/memory/genMarkSweep.cpp

@@ -210,7 +210,6 @@ void GenMarkSweep::mark_sweep_phase1(int level,
   gch->gen_process_strong_roots(level,
                                 false, // Younger gens are not roots.
                                 true,  // activate StrongRootsScope
-                                false, // not scavenging
                                 SharedHeap::SO_SystemClasses,
                                 &follow_root_closure,
                                 true,   // walk code active on stacks
@@ -296,7 +295,6 @@ void GenMarkSweep::mark_sweep_phase3(int level) {
   gch->gen_process_strong_roots(level,
                                 false, // Younger gens are not roots.
                                 true,  // activate StrongRootsScope
-                                false, // not scavenging
                                 SharedHeap::SO_AllClasses,
                                 &adjust_pointer_closure,
                                 false, // do not walk code

src/share/vm/memory/sharedHeap.cpp

@@ -139,7 +139,6 @@ SharedHeap::StrongRootsScope::~StrongRootsScope() {
 }
 
 void SharedHeap::process_strong_roots(bool activate_scope,
-                                      bool is_scavenging,
                                       ScanningOption so,
                                       OopClosure* roots,
                                       CodeBlobClosure* code_roots,
@@ -159,9 +158,11 @@ void SharedHeap::process_strong_roots(bool activate_scope,
   if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do))
     JNIHandles::oops_do(roots);
 
-  // All threads execute this; the individual threads are task groups.
   CLDToOopClosure roots_from_clds(roots);
-  CLDToOopClosure* roots_from_clds_p = (is_scavenging ? NULL : &roots_from_clds);
+  // If we limit class scanning to SO_SystemClasses we need to apply a CLD closure to
+  // CLDs which are strongly reachable from the thread stacks.
+  CLDToOopClosure* roots_from_clds_p = ((so & SO_SystemClasses) ? &roots_from_clds : NULL);
+  // All threads execute this; the individual threads are task groups.
   if (CollectedHeap::use_parallel_gc_threads()) {
     Threads::possibly_parallel_oops_do(roots, roots_from_clds_p, code_roots);
   } else {
@@ -189,9 +190,9 @@ void SharedHeap::process_strong_roots(bool activate_scope,
 
   if (!_process_strong_tasks->is_task_claimed(SH_PS_ClassLoaderDataGraph_oops_do)) {
     if (so & SO_AllClasses) {
-      ClassLoaderDataGraph::oops_do(roots, klass_closure, !is_scavenging);
+      ClassLoaderDataGraph::oops_do(roots, klass_closure, /* must_claim */ false);
     } else if (so & SO_SystemClasses) {
-      ClassLoaderDataGraph::always_strong_oops_do(roots, klass_closure, !is_scavenging);
+      ClassLoaderDataGraph::always_strong_oops_do(roots, klass_closure, /* must_claim */ true);
     }
   }
 
@@ -206,18 +207,19 @@ void SharedHeap::process_strong_roots(bool activate_scope,
   }
 
   if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) {
-    if (so & SO_CodeCache) {
+    if (so & SO_ScavengeCodeCache) {
       assert(code_roots != NULL, "must supply closure for code cache");
 
-      if (is_scavenging) {
       // We only visit parts of the CodeCache when scavenging.
       CodeCache::scavenge_root_nmethods_do(code_roots);
-      } else {
+    }
+    if (so & SO_AllCodeCache) {
+      assert(code_roots != NULL, "must supply closure for code cache");
+
       // CMSCollector uses this to do intermediate-strength collections.
       // We scan the entire code cache, since CodeCache::do_unloading is not called.
       CodeCache::blobs_do(code_roots);
     }
-    }
     // Verify that the code cache contents are not subject to
     // movement by a scavenging collection.
     DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, /*do_marking=*/ false));

src/share/vm/memory/sharedHeap.hpp

@@ -221,7 +221,8 @@ public:
     SO_AllClasses          = 0x1,
     SO_SystemClasses       = 0x2,
     SO_Strings             = 0x4,
-    SO_CodeCache           = 0x8
+    SO_AllCodeCache        = 0x8,
+    SO_ScavengeCodeCache   = 0x10
   };
 
   FlexibleWorkGang* workers() const { return _workers; }
@@ -232,9 +233,9 @@ public:
   // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
   // "SO_SystemClasses" to all the "system" classes and loaders;
   // "SO_Strings" applies the closure to all entries in StringTable;
-  // "SO_CodeCache" applies the closure to all elements of the CodeCache.
+  // "SO_AllCodeCache" applies the closure to all elements of the CodeCache.
+  // "SO_ScavengeCodeCache" applies the closure to elements on the scavenge root list in the CodeCache.
   void process_strong_roots(bool activate_scope,
-                            bool is_scavenging,
                             ScanningOption so,
                             OopClosure* roots,
                             CodeBlobClosure* code_roots,