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 /*

  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 #include "precompiled.hpp"

 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

 #include "gc_implementation/g1/satbQueue.hpp"

 #include "memory/allocation.inline.hpp"

 #include "memory/sharedHeap.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/safepoint.hpp"

 #include "runtime/thread.hpp"

 #include "runtime/vmThread.hpp"

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 void ObjPtrQueue::flush() {

   // Filter now to possibly save work later.  If filtering empties the

   // buffer then flush_impl can deallocate the buffer.

   filter();

   flush_impl();

 }

 // Return true if a SATB buffer entry refers to an object that

 // requires marking.

 //

 // The entry must point into the G1 heap.  In particular, it must not

 // be a NULL pointer.  NULL pointers are pre-filtered and never

 // inserted into a SATB buffer.

 //

 // An entry that is below the NTAMS pointer for the containing heap

 // region requires marking. Such an entry must point to a valid object.

 //

 // An entry that is at least the NTAMS pointer for the containing heap

 // region might be any of the following, none of which should be marked.

 //

 // * A reference to an object allocated since marking started.

 //   According to SATB, such objects are implicitly kept live and do

 //   not need to be dealt with via SATB buffer processing.

 //

 // * A reference to a young generation object. Young objects are

 //   handled separately and are not marked by concurrent marking.

 //

 // * A stale reference to a young generation object. If a young

 //   generation object reference is recorded and not filtered out

 //   before being moved by a young collection, the reference becomes

 //   stale.

 //

 // * A stale reference to an eagerly reclaimed humongous object.  If a

 //   humongous object is recorded and then reclaimed, the reference

 //   becomes stale.

 //

 // The stale reference cases are implicitly handled by the NTAMS

 // comparison. Because of the possibility of stale references, buffer

 // processing must be somewhat circumspect and not assume entries

 // in an unfiltered buffer refer to valid objects.

 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {

   // Includes rejection of NULL pointers.

   assert(heap->is_in_reserved(entry),

          err_msg("Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)));

   HeapRegion* region = heap->heap_region_containing_raw(entry);

   assert(region != NULL, err_msg("No region for " PTR_FORMAT, p2i(entry)));

   if (entry >= region->next_top_at_mark_start()) {

     return false;

   }

   assert(((oop)entry)->is_oop(true /* ignore mark word */),

          err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)));

   return true;

 }

 // This method removes entries from a SATB buffer that will not be

 // useful to the concurrent marking threads.  Entries are retained if

 // they require marking and are not already marked. Retained entries

 // are compacted toward the top of the buffer.

 void ObjPtrQueue::filter() {

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   void** buf = _buf;

   size_t sz = _sz;

   if (buf == NULL) {

     // nothing to do

     return;

   }

   // Used for sanity checking at the end of the loop.

   debug_only(size_t entries = 0; size_t retained = 0;)

   size_t i = sz;

   size_t new_index = sz;

   while (i > _index) {

     assert(i > 0, "we should have at least one more entry to process");

     i -= oopSize;

     debug_only(entries += 1;)

     void** p = &buf[byte_index_to_index((int) i)];

     void* entry = *p;

     // NULL the entry so that unused parts of the buffer contain NULLs

     // at the end. If we are going to retain it we will copy it to its

     // final place. If we have retained all entries we have visited so

     // far, we'll just end up copying it to the same place.

     *p = NULL;

     if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) {

       assert(new_index > 0, "we should not have already filled up the buffer");

       new_index -= oopSize;

       assert(new_index >= i,

              "new_index should never be below i, as we alwaysr compact 'up'");

       void** new_p = &buf[byte_index_to_index((int) new_index)];

       assert(new_p >= p, "the destination location should never be below "

              "the source as we always compact 'up'");

       assert(*new_p == NULL,

              "we should have already cleared the destination location");

       *new_p = entry;

       debug_only(retained += 1;)

     }

   }

 #ifdef ASSERT

   size_t entries_calc = (sz - _index) / oopSize;

   assert(entries == entries_calc, "the number of entries we counted "

          "should match the number of entries we calculated");

   size_t retained_calc = (sz - new_index) / oopSize;

   assert(retained == retained_calc, "the number of retained entries we counted "

          "should match the number of retained entries we calculated");

 #endif // ASSERT

   _index = new_index;

 }

 // This method will first apply the above filtering to the buffer. If

 // post-filtering a large enough chunk of the buffer has been cleared

 // we can re-use the buffer (instead of enqueueing it) and we can just

 // allow the mutator to carry on executing using the same buffer

 // instead of replacing it.

 bool ObjPtrQueue::should_enqueue_buffer() {

   assert(_lock == NULL || _lock->owned_by_self(),

          "we should have taken the lock before calling this");

   // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.

   // This method should only be called if there is a non-NULL buffer

   // that is full.

   assert(_index == 0, "pre-condition");

   assert(_buf != NULL, "pre-condition");

   filter();

   size_t sz = _sz;

   size_t all_entries = sz / oopSize;

   size_t retained_entries = (sz - _index) / oopSize;

   size_t perc = retained_entries * 100 / all_entries;

   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;

   return should_enqueue;

 }

 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {

   assert(SafepointSynchronize::is_at_safepoint(),

          "SATB queues must only be processed at safepoints");

   if (_buf != NULL) {

     assert(_index % sizeof(void*) == 0, "invariant");

     assert(_sz % sizeof(void*) == 0, "invariant");

     assert(_index <= _sz, "invariant");

     cl->do_buffer(_buf + byte_index_to_index((int)_index),

                   byte_index_to_index((int)(_sz - _index)));

     _index = _sz;

   }

 }

 #ifndef PRODUCT

 // Helpful for debugging

 void ObjPtrQueue::print(const char* name) {

   print(name, _buf, _index, _sz);

 }

 void ObjPtrQueue::print(const char* name,

                         void** buf, size_t index, size_t sz) {

   gclog_or_tty->print_cr("  SATB BUFFER [%s] buf: " PTR_FORMAT " "

                          "index: " SIZE_FORMAT " sz: " SIZE_FORMAT,

                          name, buf, index, sz);

 }

 #endif // PRODUCT

 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away

 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list

 #endif // _MSC_VER

 SATBMarkQueueSet::SATBMarkQueueSet() :

   PtrQueueSet(),

   _shared_satb_queue(this, true /*perm*/) { }

 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,

                                   int process_completed_threshold,

                                   Mutex* lock) {

   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);

   _shared_satb_queue.set_lock(lock);

 }

 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {

   t->satb_mark_queue().handle_zero_index();

 }

 #ifdef ASSERT

 void SATBMarkQueueSet::dump_active_states(bool expected_active) {

   gclog_or_tty->print_cr("Expected SATB active state: %s",

                          expected_active ? "ACTIVE" : "INACTIVE");

   gclog_or_tty->print_cr("Actual SATB active states:");

   gclog_or_tty->print_cr("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");

   for (JavaThread* t = Threads::first(); t; t = t->next()) {

     gclog_or_tty->print_cr("  Thread \"%s\" queue: %s", t->name(),

                            t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");

   }

   gclog_or_tty->print_cr("  Shared queue: %s",

                          shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");

 }

 void SATBMarkQueueSet::verify_active_states(bool expected_active) {

   // Verify queue set state

   if (is_active() != expected_active) {

     dump_active_states(expected_active);

     guarantee(false, "SATB queue set has an unexpected active state");

   }

   // Verify thread queue states

   for (JavaThread* t = Threads::first(); t; t = t->next()) {

     if (t->satb_mark_queue().is_active() != expected_active) {

       dump_active_states(expected_active);

       guarantee(false, "Thread SATB queue has an unexpected active state");

     }

   }

   // Verify shared queue state

   if (shared_satb_queue()->is_active() != expected_active) {

     dump_active_states(expected_active);

     guarantee(false, "Shared SATB queue has an unexpected active state");

   }

 }

 #endif // ASSERT

 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {

   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

 #ifdef ASSERT

   verify_active_states(expected_active);

 #endif // ASSERT

   _all_active = active;

   for (JavaThread* t = Threads::first(); t; t = t->next()) {

     t->satb_mark_queue().set_active(active);

   }

   shared_satb_queue()->set_active(active);

 }

 void SATBMarkQueueSet::filter_thread_buffers() {

   for(JavaThread* t = Threads::first(); t; t = t->next()) {

     t->satb_mark_queue().filter();

   }

   shared_satb_queue()->filter();

 }

 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {

   BufferNode* nd = NULL;

   {

     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

     if (_completed_buffers_head != NULL) {

       nd = _completed_buffers_head;

       _completed_buffers_head = nd->next();

       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;

       _n_completed_buffers--;

       if (_n_completed_buffers == 0) _process_completed = false;

     }

   }

   if (nd != NULL) {

     void **buf = BufferNode::make_buffer_from_node(nd);

     // Skip over NULL entries at beginning (e.g. push end) of buffer.

     // Filtering can result in non-full completed buffers; see

     // should_enqueue_buffer.

     assert(_sz % sizeof(void*) == 0, "invariant");

     size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);

     for (size_t i = 0; i < limit; ++i) {

       if (buf[i] != NULL) {

         // Found the end of the block of NULLs; process the remainder.

         cl->do_buffer(buf + i, limit - i);

         break;

       }

     }

     deallocate_buffer(buf);

     return true;

   } else {

     return false;

   }

 }

 #ifndef PRODUCT

 // Helpful for debugging

 #define SATB_PRINTER_BUFFER_SIZE 256

 void SATBMarkQueueSet::print_all(const char* msg) {

   char buffer[SATB_PRINTER_BUFFER_SIZE];

   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   gclog_or_tty->cr();

   gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);

   BufferNode* nd = _completed_buffers_head;

   int i = 0;

   while (nd != NULL) {

     void** buf = BufferNode::make_buffer_from_node(nd);

     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);

     ObjPtrQueue::print(buffer, buf, 0, _sz);

     nd = nd->next();

     i += 1;

   }

   for (JavaThread* t = Threads::first(); t; t = t->next()) {

     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());

     t->satb_mark_queue().print(buffer);

   }

   shared_satb_queue()->print("Shared");

   gclog_or_tty->cr();

 }

 #endif // PRODUCT

 void SATBMarkQueueSet::abandon_partial_marking() {

   BufferNode* buffers_to_delete = NULL;

   {

     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

     while (_completed_buffers_head != NULL) {

       BufferNode* nd = _completed_buffers_head;

       _completed_buffers_head = nd->next();

       nd->set_next(buffers_to_delete);

       buffers_to_delete = nd;

     }

     _completed_buffers_tail = NULL;

     _n_completed_buffers = 0;

     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());

   }

   while (buffers_to_delete != NULL) {

     BufferNode* nd = buffers_to_delete;

     buffers_to_delete = nd->next();

     deallocate_buffer(BufferNode::make_buffer_from_node(nd));

   }

   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   // So we can safely manipulate these queues.

   for (JavaThread* t = Threads::first(); t; t = t->next()) {

     t->satb_mark_queue().reset();

   }

  shared_satb_queue()->reset();

 }