1 /*
2 * Copyright (c) 1998, 2006, 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 //
26 // Prioritized queue of VM operations.
27 //
28 // Encapsulates both queue management and
29 // and priority policy
30 //
31 class VMOperationQueue : public CHeapObj {
32 private:
33 enum Priorities {
34 SafepointPriority, // Highest priority (operation executed at a safepoint)
35 MediumPriority, // Medium priority
36 nof_priorities
37 };
38
39 // We maintain a doubled linked list, with explicit count.
40 int _queue_length[nof_priorities];
41 int _queue_counter;
42 VM_Operation* _queue [nof_priorities];
43 // we also allow the vmThread to register the ops it has drained so we
44 // can scan them from oops_do
45 VM_Operation* _drain_list;
46
47 // Double-linked non-empty list insert.
48 void insert(VM_Operation* q,VM_Operation* n);
49 void unlink(VM_Operation* q);
50
51 // Basic queue manipulation
52 bool queue_empty (int prio);
53 void queue_add_front (int prio, VM_Operation *op);
54 void queue_add_back (int prio, VM_Operation *op);
55 VM_Operation* queue_remove_front(int prio);
56 void queue_oops_do(int queue, OopClosure* f);
57 void drain_list_oops_do(OopClosure* f);
58 VM_Operation* queue_drain(int prio);
59 // lock-free query: may return the wrong answer but must not break
60 bool queue_peek(int prio) { return _queue_length[prio] > 0; }
61
62 public:
63 VMOperationQueue();
64
65 // Highlevel operations. Encapsulates policy
66 bool add(VM_Operation *op);
67 VM_Operation* remove_next(); // Returns next or null
68 VM_Operation* remove_next_at_safepoint_priority() { return queue_remove_front(SafepointPriority); }
69 VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }
70 void set_drain_list(VM_Operation* list) { _drain_list = list; }
71 bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }
72
73 // GC support
74 void oops_do(OopClosure* f);
75
76 void verify_queue(int prio) PRODUCT_RETURN;
77 };
78
79
80 //
81 // A single VMThread (the primordial thread) spawns all other threads
82 // and is itself used by other threads to offload heavy vm operations
83 // like scavenge, garbage_collect etc.
84 //
85
86 class VMThread: public NamedThread {
87 private:
88 static ThreadPriority _current_priority;
89
90 static bool _should_terminate;
91 static bool _terminated;
92 static Monitor * _terminate_lock;
93 static PerfCounter* _perf_accumulated_vm_operation_time;
94
95 void evaluate_operation(VM_Operation* op);
96 public:
97 // Constructor
98 VMThread();
99
100 // Tester
101 bool is_VM_thread() const { return true; }
102 bool is_GC_thread() const { return true; }
103
104 // The ever running loop for the VMThread
105 void loop();
106
107 // Called to stop the VM thread
108 static void wait_for_vm_thread_exit();
109 static bool should_terminate() { return _should_terminate; }
110 static bool is_terminated() { return _terminated == true; }
111
112 // Execution of vm operation
113 static void execute(VM_Operation* op);
114
115 // Returns the current vm operation if any.
116 static VM_Operation* vm_operation() { return _cur_vm_operation; }
117
118 // Returns the single instance of VMThread.
119 static VMThread* vm_thread() { return _vm_thread; }
120
121 // GC support
122 void oops_do(OopClosure* f, CodeBlobClosure* cf);
123
124 // Debugging
125 void print_on(outputStream* st) const;
126 void print() const { print_on(tty); }
127 void verify();
128
129 // Performance measurement
130 static PerfCounter* perf_accumulated_vm_operation_time() { return _perf_accumulated_vm_operation_time; }
131
132 // Entry for starting vm thread
133 virtual void run();
134
135 // Creations/Destructions
136 static void create();
137 static void destroy();
138
139 private:
140 // VM_Operation support
141 static VM_Operation* _cur_vm_operation; // Current VM operation
142 static VMOperationQueue* _vm_queue; // Queue (w/ policy) of VM operations
143
144 // Pointer to single-instance of VM thread
145 static VMThread* _vm_thread;
146 };