/*

 * Copyright (c) 2019, 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

 * 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/shared/scavengableNMethods.hpp"

#include "gc/shared/scavengableNMethodsData.hpp"

#include "runtime/mutexLocker.hpp"

#include "utilities/debug.hpp"

static ScavengableNMethodsData gc_data(nmethod* nm) {

  return ScavengableNMethodsData(nm);

}

nmethod* ScavengableNMethods::_head = NULL;

BoolObjectClosure* ScavengableNMethods::_is_scavengable = NULL;

void ScavengableNMethods::initialize(BoolObjectClosure* is_scavengable) {

  _is_scavengable = is_scavengable;

}

// Conditionally adds the nmethod to the list if it is

// not already on the list and has a scavengeable root.

void ScavengableNMethods::register_nmethod(nmethod* nm) {

  assert_locked_or_safepoint(CodeCache_lock);

  ScavengableNMethodsData data = gc_data(nm);

  if (data.on_list() || !has_scavengable_oops(nm)) {

    return;

  }

  data.set_on_list();

  data.set_next(_head);

  _head = nm;

}

void ScavengableNMethods::unregister_nmethod(nmethod* nm) {

  assert_locked_or_safepoint(CodeCache_lock);

  if (gc_data(nm).on_list()) {

    nmethod* prev = NULL;

    for (nmethod* cur = _head; cur != NULL; cur = gc_data(cur).next()) {

      if (cur == nm) {

        unlist_nmethod(cur, prev);

        return;

      }

      prev = cur;

    }

  }

}

#ifndef PRODUCT

class DebugScavengableOops: public OopClosure {

  BoolObjectClosure* _is_scavengable;

  nmethod*           _nm;

  bool               _ok;

public:

  DebugScavengableOops(BoolObjectClosure* is_scavengable, nmethod* nm) :

      _is_scavengable(is_scavengable),

      _nm(nm),

      _ok(true) { }

  bool ok() { return _ok; }

  virtual void do_oop(oop* p) {

    if (*p == NULL || !_is_scavengable->do_object_b(*p)) {

      return;

    }

    if (_ok) {

      _nm->print_nmethod(true);

      _ok = false;

    }

    tty->print_cr("*** scavengable oop " PTR_FORMAT " found at " PTR_FORMAT " (offset %d)",

                  p2i(*p), p2i(p), (int)((intptr_t)p - (intptr_t)_nm));

    (*p)->print();

  }

  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }

};

#endif // PRODUCT

void ScavengableNMethods::verify_nmethod(nmethod* nm) {

#ifndef PRODUCT

  if (!gc_data(nm).on_list()) {

    // Actually look inside, to verify the claim that it's clean.

    DebugScavengableOops cl(_is_scavengable, nm);

    nm->oops_do(&cl);

    if (!cl.ok())

      fatal("found an unadvertised bad scavengable oop in the code cache");

  }

  assert(gc_data(nm).not_marked(), "");

#endif // PRODUCT

}

class HasScavengableOops: public OopClosure {

  BoolObjectClosure* _is_scavengable;

  bool               _found;

public:

  HasScavengableOops(BoolObjectClosure* is_scavengable, nmethod* nm) :

      _is_scavengable(is_scavengable),

      _found(false) {}

  bool found() { return _found; }

  virtual void do_oop(oop* p) {

    if (!_found && *p != NULL && _is_scavengable->do_object_b(*p)) {

      _found = true;

    }

  }

  virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }

};

bool ScavengableNMethods::has_scavengable_oops(nmethod* nm) {

  HasScavengableOops cl(_is_scavengable, nm);

  nm->oops_do(&cl);

  return cl.found();

}

// Walk the list of methods which might contain oops to the java heap.

void ScavengableNMethods::nmethods_do_and_prune(CodeBlobToOopClosure* cl) {

  assert_locked_or_safepoint(CodeCache_lock);

  debug_only(mark_on_list_nmethods());

  nmethod* prev = NULL;

  nmethod* cur = _head;

  while (cur != NULL) {

    assert(cur->is_alive(), "Must be");

    ScavengableNMethodsData data = gc_data(cur);

    debug_only(data.clear_marked());

    assert(data.on_list(), "else shouldn't be on this list");

    if (cl != NULL) {

      cl->do_code_blob(cur);

    }

    nmethod* const next = data.next();

    if (!has_scavengable_oops(cur)) {

      unlist_nmethod(cur, prev);

    } else {

      prev = cur;

    }

    cur = next;

  }

  // Check for stray marks.

  debug_only(verify_unlisted_nmethods(NULL));

}

void ScavengableNMethods::prune_nmethods() {

  nmethods_do_and_prune(NULL /* No closure */);

}

// Walk the list of methods which might contain oops to the java heap.

void ScavengableNMethods::nmethods_do(CodeBlobToOopClosure* cl) {

  nmethods_do_and_prune(cl);

}

#ifndef PRODUCT

void ScavengableNMethods::asserted_non_scavengable_nmethods_do(CodeBlobClosure* cl) {

  // While we are here, verify the integrity of the list.

  mark_on_list_nmethods();

  for (nmethod* cur = _head; cur != NULL; cur = gc_data(cur).next()) {

    assert(gc_data(cur).on_list(), "else shouldn't be on this list");

    gc_data(cur).clear_marked();

  }

  verify_unlisted_nmethods(cl);

}

#endif // PRODUCT

void ScavengableNMethods::unlist_nmethod(nmethod* nm, nmethod* prev) {

  assert_locked_or_safepoint(CodeCache_lock);

  assert((prev == NULL && _head == nm) ||

         (prev != NULL && gc_data(prev).next() == nm), "precondition");

  ScavengableNMethodsData data = gc_data(nm);

  if (prev == NULL) {

    _head = data.next();

  } else {

    gc_data(prev).set_next(data.next());

  }

  data.set_next(NULL);

  data.clear_on_list();

}

#ifndef PRODUCT

// Temporarily mark nmethods that are claimed to be on the scavenge list.

void ScavengableNMethods::mark_on_list_nmethods() {

  NMethodIterator iter(NMethodIterator::only_alive);

  while(iter.next()) {

    nmethod* nm = iter.method();

    ScavengableNMethodsData data = gc_data(nm);

    assert(data.not_marked(), "clean state");

    if (data.on_list())

      data.set_marked();

  }

}

// If the closure is given, run it on the unlisted nmethods.

// Also make sure that the effects of mark_on_list_nmethods is gone.

void ScavengableNMethods::verify_unlisted_nmethods(CodeBlobClosure* cl) {

  NMethodIterator iter(NMethodIterator::only_alive);

  while(iter.next()) {

    nmethod* nm = iter.method();

    verify_nmethod(nm);

    if (cl != NULL && !gc_data(nm).on_list()) {

      cl->do_code_blob(nm);

    }

  }

}

#endif //PRODUCT