/*

 * Copyright (c) 2017, 2019, Red Hat, Inc. All rights reserved.

 *

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "code/codeCache.hpp"

#include "code/nmethod.hpp"

#include "gc/shenandoah/shenandoahHeap.inline.hpp"

#include "gc/shenandoah/shenandoahCodeRoots.hpp"

#include "gc/shenandoah/shenandoahUtils.hpp"

#include "memory/resourceArea.hpp"

#include "memory/universe.hpp"

ShenandoahParallelCodeCacheIterator::ShenandoahParallelCodeCacheIterator(const GrowableArray<CodeHeap*>* heaps) {

  _length = heaps->length();

  _iters = NEW_C_HEAP_ARRAY(ShenandoahParallelCodeHeapIterator, _length, mtGC);

  for (int h = 0; h < _length; h++) {

    _iters[h] = ShenandoahParallelCodeHeapIterator(heaps->at(h));

  }

}

ShenandoahParallelCodeCacheIterator::~ShenandoahParallelCodeCacheIterator() {

  FREE_C_HEAP_ARRAY(ParallelCodeHeapIterator, _iters);

}

void ShenandoahParallelCodeCacheIterator::parallel_blobs_do(CodeBlobClosure* f) {

  for (int c = 0; c < _length; c++) {

    _iters[c].parallel_blobs_do(f);

  }

}

ShenandoahParallelCodeHeapIterator::ShenandoahParallelCodeHeapIterator(CodeHeap* heap) :

        _heap(heap), _claimed_idx(0), _finished(false) {

}

void ShenandoahParallelCodeHeapIterator::parallel_blobs_do(CodeBlobClosure* f) {

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

  /*

   * Parallel code heap walk.

   *

   * This code makes all threads scan all code heaps, but only one thread would execute the

   * closure on given blob. This is achieved by recording the "claimed" blocks: if a thread

   * had claimed the block, it can process all blobs in it. Others have to fast-forward to

   * next attempt without processing.

   *

   * Late threads would return immediately if iterator is finished.

   */

  if (_finished) {

    return;

  }

  int stride = 256; // educated guess

  int stride_mask = stride - 1;

  assert (is_power_of_2(stride), "sanity");

  int count = 0;

  bool process_block = true;

  for (CodeBlob *cb = CodeCache::first_blob(_heap); cb != NULL; cb = CodeCache::next_blob(_heap, cb)) {

    int current = count++;

    if ((current & stride_mask) == 0) {

      process_block = (current >= _claimed_idx) &&

                      (Atomic::cmpxchg(current + stride, &_claimed_idx, current) == current);

    }

    if (process_block) {

      if (cb->is_alive()) {

        f->do_code_blob(cb);

#ifdef ASSERT

        if (cb->is_nmethod())

          Universe::heap()->verify_nmethod((nmethod*)cb);

#endif

      }

    }

  }

  _finished = true;

}

class ShenandoahNMethodOopDetector : public OopClosure {

private:

  ResourceMark rm; // For growable array allocation below.

  GrowableArray<oop*> _oops;

public:

  ShenandoahNMethodOopDetector() : _oops(10) {};

  void do_oop(oop* o) {

    _oops.append(o);

  }

  void do_oop(narrowOop* o) {

    fatal("NMethods should not have compressed oops embedded.");

  }

  GrowableArray<oop*>* oops() {

    return &_oops;

  }

  bool has_oops() {

    return !_oops.is_empty();

  }

};

GrowableArray<ShenandoahNMethod*>* ShenandoahCodeRoots::_recorded_nms;

ShenandoahLock                     ShenandoahCodeRoots::_recorded_nms_lock;

void ShenandoahCodeRoots::initialize() {

  _recorded_nms = new (ResourceObj::C_HEAP, mtGC) GrowableArray<ShenandoahNMethod*>(100, true, mtGC);

}

void ShenandoahCodeRoots::add_nmethod(nmethod* nm) {

  switch (ShenandoahCodeRootsStyle) {

    case 0:

    case 1:

      break;

    case 2: {

      assert_locked_or_safepoint(CodeCache_lock);

      ShenandoahLocker locker(CodeCache_lock->owned_by_self() ? NULL : &_recorded_nms_lock);

      ShenandoahNMethodOopDetector detector;

      nm->oops_do(&detector);

      if (detector.has_oops()) {

        ShenandoahNMethod* nmr = new ShenandoahNMethod(nm, detector.oops());

        nmr->assert_alive_and_correct();

        int idx = _recorded_nms->find(nm, ShenandoahNMethod::find_with_nmethod);

        if (idx != -1) {

          ShenandoahNMethod* old = _recorded_nms->at(idx);

          _recorded_nms->at_put(idx, nmr);

          delete old;

        } else {

          _recorded_nms->append(nmr);

        }

      }

      break;

    }

    default:

      ShouldNotReachHere();

  }

};

void ShenandoahCodeRoots::remove_nmethod(nmethod* nm) {

  switch (ShenandoahCodeRootsStyle) {

    case 0:

    case 1: {

      break;

    }

    case 2: {

      assert_locked_or_safepoint(CodeCache_lock);

      ShenandoahLocker locker(CodeCache_lock->owned_by_self() ? NULL : &_recorded_nms_lock);

      ShenandoahNMethodOopDetector detector;

      nm->oops_do(&detector, /* allow_dead = */ true);

      if (detector.has_oops()) {

        int idx = _recorded_nms->find(nm, ShenandoahNMethod::find_with_nmethod);

        assert(idx != -1, "nmethod " PTR_FORMAT " should be registered", p2i(nm));

        ShenandoahNMethod* old = _recorded_nms->at(idx);

        old->assert_same_oops(detector.oops());

        _recorded_nms->delete_at(idx);

        delete old;

      }

      break;

    }

    default:

      ShouldNotReachHere();

  }

}

ShenandoahCodeRootsIterator::ShenandoahCodeRootsIterator() :

        _heap(ShenandoahHeap::heap()),

        _par_iterator(CodeCache::heaps()),

        _claimed(0) {

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

  assert(!Thread::current()->is_Worker_thread(), "Should not be acquired by workers");

  switch (ShenandoahCodeRootsStyle) {

    case 0:

    case 1: {

      // No need to do anything here

      break;

    }

    case 2: {

      CodeCache_lock->lock_without_safepoint_check();

      break;

    }

    default:

      ShouldNotReachHere();

  }

}

ShenandoahCodeRootsIterator::~ShenandoahCodeRootsIterator() {

  switch (ShenandoahCodeRootsStyle) {

    case 0:

    case 1: {

      // No need to do anything here

      break;

    }

    case 2: {

      CodeCache_lock->unlock();

      break;

    }

    default:

      ShouldNotReachHere();

  }

}

template<bool CSET_FILTER>

void ShenandoahCodeRootsIterator::dispatch_parallel_blobs_do(CodeBlobClosure *f) {

  switch (ShenandoahCodeRootsStyle) {

    case 0: {

      if (_seq_claimed.try_set()) {

        CodeCache::blobs_do(f);

      }

      break;

    }

    case 1: {

      _par_iterator.parallel_blobs_do(f);

      break;

    }

    case 2: {

      ShenandoahCodeRootsIterator::fast_parallel_blobs_do<CSET_FILTER>(f);

      break;

    }

    default:

      ShouldNotReachHere();

  }

}

void ShenandoahAllCodeRootsIterator::possibly_parallel_blobs_do(CodeBlobClosure *f) {

  ShenandoahCodeRootsIterator::dispatch_parallel_blobs_do<false>(f);

}

void ShenandoahCsetCodeRootsIterator::possibly_parallel_blobs_do(CodeBlobClosure *f) {

  ShenandoahCodeRootsIterator::dispatch_parallel_blobs_do<true>(f);

}

template <bool CSET_FILTER>

void ShenandoahCodeRootsIterator::fast_parallel_blobs_do(CodeBlobClosure *f) {

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

  size_t stride = 256; // educated guess

  GrowableArray<ShenandoahNMethod*>* list = ShenandoahCodeRoots::_recorded_nms;

  size_t max = (size_t)list->length();

  while (_claimed < max) {

    size_t start = cur;

    size_t end = MIN2(cur + stride, max);

    if (start >= max) break;

    for (size_t idx = start; idx < end; idx++) {

      ShenandoahNMethod* nmr = list->at((int) idx);

      nmr->assert_alive_and_correct();

      if (CSET_FILTER && !nmr->has_cset_oops(_heap)) {

        continue;

      }

      f->do_code_blob(nmr->nm());

    }

  }

}

ShenandoahNMethod::ShenandoahNMethod(nmethod* nm, GrowableArray<oop*>* oops) {

  _nm = nm;

  _oops = NEW_C_HEAP_ARRAY(oop*, oops->length(), mtGC);

  _oops_count = oops->length();

  for (int c = 0; c < _oops_count; c++) {

    _oops[c] = oops->at(c);

  }

}

ShenandoahNMethod::~ShenandoahNMethod() {

  if (_oops != NULL) {

    FREE_C_HEAP_ARRAY(oop*, _oops);

  }

}

bool ShenandoahNMethod::has_cset_oops(ShenandoahHeap *heap) {

  for (int c = 0; c < _oops_count; c++) {

    oop o = RawAccess<>::oop_load(_oops[c]);

    if (heap->in_collection_set(o)) {

      return true;

    }

  }

  return false;

}

#ifdef ASSERT

void ShenandoahNMethod::assert_alive_and_correct() {

  assert(_nm->is_alive(), "only alive nmethods here");

  assert(_oops_count > 0, "should have filtered nmethods without oops before");

  ShenandoahHeap* heap = ShenandoahHeap::heap();

  for (int c = 0; c < _oops_count; c++) {

    oop *loc = _oops[c];

    assert(_nm->code_contains((address) loc) || _nm->oops_contains(loc), "nmethod should contain the oop*");

    oop o = RawAccess<>::oop_load(loc);

    shenandoah_assert_correct_except(loc, o,

             o == NULL ||

             heap->is_full_gc_move_in_progress() ||

             (VMThread::vm_operation() != NULL) && (VMThread::vm_operation()->type() == VM_Operation::VMOp_HeapWalkOperation)

    );

  }

}

void ShenandoahNMethod::assert_same_oops(GrowableArray<oop*>* oops) {

  assert(_oops_count == oops->length(), "should have the same number of oop*");

  for (int c = 0; c < _oops_count; c++) {

    assert(_oops[c] == oops->at(c), "should be the same oop*");

  }

}

#endif