1/*
2 * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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23 */
24
25#ifndef SHARE_RUNTIME_VMTHREAD_HPP
26#define SHARE_RUNTIME_VMTHREAD_HPP
27
28#include "runtime/perfData.hpp"
29#include "runtime/thread.hpp"
30#include "runtime/task.hpp"
31#include "runtime/vmOperations.hpp"
32
33//
34// Prioritized queue of VM operations.
35//
36// Encapsulates both queue management and
37// and priority policy
38//
39class VMOperationQueue : public CHeapObj<mtInternal> {
40 private:
41 enum Priorities {
42 SafepointPriority, // Highest priority (operation executed at a safepoint)
43 MediumPriority, // Medium priority
44 nof_priorities
45 };
46
47 // We maintain a doubled linked list, with explicit count.
48 int _queue_length[nof_priorities];
49 int _queue_counter;
50 VM_Operation* _queue [nof_priorities];
51 // we also allow the vmThread to register the ops it has drained so we
52 // can scan them from oops_do
53 VM_Operation* _drain_list;
54
55 // Double-linked non-empty list insert.
56 void insert(VM_Operation* q,VM_Operation* n);
57 void unlink(VM_Operation* q);
58
59 // Basic queue manipulation
60 bool queue_empty (int prio);
61 void queue_add_front (int prio, VM_Operation *op);
62 void queue_add_back (int prio, VM_Operation *op);
63 VM_Operation* queue_remove_front(int prio);
64 void queue_oops_do(int queue, OopClosure* f);
65 void drain_list_oops_do(OopClosure* f);
66 VM_Operation* queue_drain(int prio);
67 // lock-free query: may return the wrong answer but must not break
68 bool queue_peek(int prio) { return _queue_length[prio] > 0; }
69
70 public:
71 VMOperationQueue();
72
73 // Highlevel operations. Encapsulates policy
74 void add(VM_Operation *op);
75 VM_Operation* remove_next(); // Returns next or null
76 VM_Operation* remove_next_at_safepoint_priority() { return queue_remove_front(SafepointPriority); }
77 VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }
78 void set_drain_list(VM_Operation* list) { _drain_list = list; }
79 bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }
80
81 // GC support
82 void oops_do(OopClosure* f);
83
84 void verify_queue(int prio) PRODUCT_RETURN;
85};
86
87
88// VM operation timeout handling: warn or abort the VM when VM operation takes
89// too long. Periodic tasks do not participate in safepoint protocol, and therefore
90// can fire when application threads are stopped.
91
92class VMOperationTimeoutTask : public PeriodicTask {
93private:
94 volatile int _armed;
95 jlong _arm_time;
96
97public:
98 VMOperationTimeoutTask(size_t interval_time) :
99 PeriodicTask(interval_time), _armed(0), _arm_time(0) {}
100
101 virtual void task();
102
103 bool is_armed();
104 void arm();
105 void disarm();
106};
107
108//
109// A single VMThread (the primordial thread) spawns all other threads
110// and is itself used by other threads to offload heavy vm operations
111// like scavenge, garbage_collect etc.
112//
113
114class VMThread: public NamedThread {
115 private:
116 static ThreadPriority _current_priority;
117
118 static bool _should_terminate;
119 static bool _terminated;
120 static Monitor * _terminate_lock;
121 static PerfCounter* _perf_accumulated_vm_operation_time;
122 static uint64_t _coalesced_count;
123
124 static VMOperationTimeoutTask* _timeout_task;
125
126 static VM_Operation* no_op_safepoint();
127
128 void evaluate_operation(VM_Operation* op);
129
130 public:
131 // Constructor
132 VMThread();
133
134 // No destruction allowed
135 ~VMThread() {
136 guarantee(false, "VMThread deletion must fix the race with VM termination");
137 }
138
139
140 // Tester
141 bool is_VM_thread() const { return true; }
142 bool is_GC_thread() const { return true; }
143
144 // The ever running loop for the VMThread
145 void loop();
146
147 // Called to stop the VM thread
148 static void wait_for_vm_thread_exit();
149 static bool should_terminate() { return _should_terminate; }
150 static bool is_terminated() { return _terminated == true; }
151
152 // Execution of vm operation
153 static void execute(VM_Operation* op);
154
155 // Returns the current vm operation if any.
156 static VM_Operation* vm_operation() { return _cur_vm_operation; }
157 static VM_Operation::VMOp_Type vm_op_type() { return _cur_vm_operation->type(); }
158 static uint64_t get_coalesced_count() { return _coalesced_count; }
159
160 // Returns the single instance of VMThread.
161 static VMThread* vm_thread() { return _vm_thread; }
162
163 // GC support
164 void oops_do(OopClosure* f, CodeBlobClosure* cf);
165
166 void verify();
167
168 // Performance measurement
169 static PerfCounter* perf_accumulated_vm_operation_time() { return _perf_accumulated_vm_operation_time; }
170
171 // Entry for starting vm thread
172 virtual void run();
173
174 // Creations/Destructions
175 static void create();
176 static void destroy();
177
178 private:
179 // VM_Operation support
180 static VM_Operation* _cur_vm_operation; // Current VM operation
181 static VMOperationQueue* _vm_queue; // Queue (w/ policy) of VM operations
182
183 // Pointer to single-instance of VM thread
184 static VMThread* _vm_thread;
185};
186
187#endif // SHARE_RUNTIME_VMTHREAD_HPP
188