1 /*
2 * Copyright (c) 1998, 2016, 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.
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23 */
24
25 #ifndef SHARE_VM_RUNTIME_VMTHREAD_HPP
26 #define SHARE_VM_RUNTIME_VMTHREAD_HPP
27
28 #include "runtime/perfData.hpp"
29 #include "runtime/thread.hpp"
30 #include "runtime/vmOperations.hpp"
31
32 //
33 // Prioritized queue of VM operations.
34 //
35 // Encapsulates both queue management and
36 // and priority policy
37 //
38 class VMOperationQueue : public CHeapObj<mtInternal> {
39 private:
40 enum Priorities {
41 SafepointPriority, // Highest priority (operation executed at a safepoint)
42 MediumPriority, // Medium priority
43 nof_priorities
44 };
45
46 // We maintain a doubled linked list, with explicit count.
47 int _queue_length[nof_priorities];
48 int _queue_counter;
49 VM_Operation* _queue [nof_priorities];
50 // we also allow the vmThread to register the ops it has drained so we
51 // can scan them from oops_do
52 VM_Operation* _drain_list;
53
54 // Double-linked non-empty list insert.
55 void insert(VM_Operation* q,VM_Operation* n);
56 void unlink(VM_Operation* q);
57
58 // Basic queue manipulation
59 bool queue_empty (int prio);
60 void queue_add_front (int prio, VM_Operation *op);
61 void queue_add_back (int prio, VM_Operation *op);
62 VM_Operation* queue_remove_front(int prio);
63 void queue_oops_do(int queue, OopClosure* f);
64 void drain_list_oops_do(OopClosure* f);
65 VM_Operation* queue_drain(int prio);
66 // lock-free query: may return the wrong answer but must not break
67 bool queue_peek(int prio) { return _queue_length[prio] > 0; }
68
69 public:
70 VMOperationQueue();
71
72 // Highlevel operations. Encapsulates policy
73 bool add(VM_Operation *op);
74 VM_Operation* remove_next(); // Returns next or null
75 VM_Operation* remove_next_at_safepoint_priority() { return queue_remove_front(SafepointPriority); }
76 VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }
77 void set_drain_list(VM_Operation* list) { _drain_list = list; }
78 bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }
79
80 // GC support
81 void oops_do(OopClosure* f);
82
83 void verify_queue(int prio) PRODUCT_RETURN;
84 };
85
86
87 //
88 // A single VMThread (the primordial thread) spawns all other threads
89 // and is itself used by other threads to offload heavy vm operations
90 // like scavenge, garbage_collect etc.
91 //
92
93 class VMThread: public NamedThread {
94 private:
95 static ThreadPriority _current_priority;
96
97 static bool _should_terminate;
98 static bool _terminated;
99 static Monitor * _terminate_lock;
100 static PerfCounter* _perf_accumulated_vm_operation_time;
101
102 static const char* _no_op_reason;
103
104 static bool no_op_safepoint_needed(bool check_time);
105
106 void evaluate_operation(VM_Operation* op);
107
108 public:
109 // Constructor
110 VMThread();
111
112 // No destruction allowed
113 ~VMThread() {
114 guarantee(false, "VMThread deletion must fix the race with VM termination");
115 }
116
117
118 // Tester
119 bool is_VM_thread() const { return true; }
120 bool is_GC_thread() const { return true; }
121
122 // The ever running loop for the VMThread
123 void loop();
124
125 // Called to stop the VM thread
126 static void wait_for_vm_thread_exit();
127 static bool should_terminate() { return _should_terminate; }
128 static bool is_terminated() { return _terminated == true; }
129
130 // Execution of vm operation
131 static void execute(VM_Operation* op);
132
133 // Returns the current vm operation if any.
134 static VM_Operation* vm_operation() { return _cur_vm_operation; }
135
136 // Returns the current vm operation name or set reason
137 static const char* vm_safepoint_description() { return _cur_vm_operation != NULL ? _cur_vm_operation->name() : _no_op_reason; };
138
139 // Returns the single instance of VMThread.
140 static VMThread* vm_thread() { return _vm_thread; }
141
142 // GC support
143 void oops_do(OopClosure* f, CodeBlobClosure* cf);
144
145 void verify();
146
147 // Performance measurement
148 static PerfCounter* perf_accumulated_vm_operation_time() { return _perf_accumulated_vm_operation_time; }
149
150 // Entry for starting vm thread
151 virtual void run();
152
153 // Creations/Destructions
154 static void create();
155 static void destroy();
156
157 private:
158 // VM_Operation support
159 static VM_Operation* _cur_vm_operation; // Current VM operation
160 static VMOperationQueue* _vm_queue; // Queue (w/ policy) of VM operations
161
162 // Pointer to single-instance of VM thread
163 static VMThread* _vm_thread;
164 };
165
166 #endif // SHARE_VM_RUNTIME_VMTHREAD_HPP