1/*
2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25#ifndef SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP
26#define SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP
27
28#include "memory/allocation.hpp"
29#include "oops/oop.hpp"
30#include "runtime/handles.hpp"
31#include "runtime/perfData.hpp"
32#include "runtime/safepoint.hpp"
33
34class nmethod;
35class DepChange;
36
37//
38// nmethodBucket is used to record dependent nmethods for
39// deoptimization.  nmethod dependencies are actually <klass, method>
40// pairs but we really only care about the klass part for purposes of
41// finding nmethods which might need to be deoptimized.  Instead of
42// recording the method, a count of how many times a particular nmethod
43// was recorded is kept.  This ensures that any recording errors are
44// noticed since an nmethod should be removed as many times are it's
45// added.
46//
47class nmethodBucket: public CHeapObj<mtClass> {
48  friend class VMStructs;
49 private:
50  nmethod*       _nmethod;
51  int            _count;
52  nmethodBucket* _next;
53
54 public:
55  nmethodBucket(nmethod* nmethod, nmethodBucket* next) :
56   _nmethod(nmethod), _next(next), _count(1) {}
57
58  int count()                             { return _count; }
59  int increment()                         { _count += 1; return _count; }
60  int decrement();
61  nmethodBucket* next()                   { return _next; }
62  void set_next(nmethodBucket* b)         { _next = b; }
63  nmethod* get_nmethod()                  { return _nmethod; }
64};
65
66//
67// Utility class to manipulate nmethod dependency context.
68// The context consists of nmethodBucket* (a head of a linked list)
69// and a boolean flag (does the list contains stale entries). The structure is
70// encoded as an intptr_t: lower bit is used for the flag. It is possible since
71// nmethodBucket* is aligned - the structure is malloc'ed in C heap.
72// Dependency context can be attached either to an InstanceKlass (_dep_context field)
73// or CallSiteContext oop for call_site_target dependencies (see javaClasses.hpp).
74// DependencyContext class operates on some location which holds a intptr_t value.
75//
76class DependencyContext : public StackObj {
77  friend class VMStructs;
78  friend class TestDependencyContext;
79 private:
80  enum TagBits { _has_stale_entries_bit = 1, _has_stale_entries_mask = 1 };
81
82  intptr_t* _dependency_context_addr;
83
84  void set_dependencies(nmethodBucket* b) {
85    assert((intptr_t(b) & _has_stale_entries_mask) == 0, "should be aligned");
86    if (has_stale_entries()) {
87      *_dependency_context_addr = intptr_t(b) | _has_stale_entries_mask;
88    } else {
89      *_dependency_context_addr = intptr_t(b);
90    }
91  }
92
93  void set_has_stale_entries(bool x) {
94    if (x) {
95      *_dependency_context_addr |= _has_stale_entries_mask;
96    } else {
97      *_dependency_context_addr &= ~_has_stale_entries_mask;
98    }
99  }
100
101  nmethodBucket* dependencies() {
102    intptr_t value = *_dependency_context_addr;
103    return (nmethodBucket*) (value & ~_has_stale_entries_mask);
104  }
105
106  bool has_stale_entries() const {
107    intptr_t value = *_dependency_context_addr;
108    return (value & _has_stale_entries_mask) != 0;
109  }
110
111  static PerfCounter* _perf_total_buckets_allocated_count;
112  static PerfCounter* _perf_total_buckets_deallocated_count;
113  static PerfCounter* _perf_total_buckets_stale_count;
114  static PerfCounter* _perf_total_buckets_stale_acc_count;
115
116 public:
117#ifdef ASSERT
118  // Safepoints are forbidden during DC lifetime. GC can invalidate
119  // _dependency_context_addr if it relocates the holder
120  // (e.g. CallSiteContext Java object).
121  int _safepoint_counter;
122
123  DependencyContext(intptr_t* addr) : _dependency_context_addr(addr),
124    _safepoint_counter(SafepointSynchronize::_safepoint_counter) {}
125
126  ~DependencyContext() {
127    assert(_safepoint_counter == SafepointSynchronize::_safepoint_counter, "safepoint happened");
128  }
129#else
130  DependencyContext(intptr_t* addr) : _dependency_context_addr(addr) {}
131#endif // ASSERT
132
133  static const intptr_t EMPTY = 0; // dependencies = NULL, has_stale_entries = false
134
135  static void init();
136
137  int  mark_dependent_nmethods(DepChange& changes);
138  void add_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
139  void remove_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
140  int  remove_all_dependents();
141
142  void expunge_stale_entries();
143
144  // Unsafe deallocation of nmethodBuckets. Used in IK::release_C_heap_structures
145  // to clean up the context possibly containing live entries pointing to unloaded nmethods.
146  void wipe();
147
148#ifndef PRODUCT
149  void print_dependent_nmethods(bool verbose);
150  bool is_dependent_nmethod(nmethod* nm);
151  bool find_stale_entries();
152#endif //PRODUCT
153};
154#endif // SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP
155