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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 // VM operation timeout handling: warn or abort the VM when VM operation takes
34 // too long. Periodic tasks do not participate in safepoint protocol, and therefore
35 // can fire when application threads are stopped.
36 
37 class VMOperationTimeoutTask : public PeriodicTask {
38 private:
39   volatile int _armed;
40   jlong _arm_time;
41 
42 public:
VMOperationTimeoutTask(size_t interval_time)43   VMOperationTimeoutTask(size_t interval_time) :
44           PeriodicTask(interval_time), _armed(0), _arm_time(0) {}
45 
46   virtual void task();
47 
48   bool is_armed();
49   void arm();
50   void disarm();
51 };
52 
53 //
54 // A single VMThread (the primordial thread) spawns all other threads
55 // and is itself used by other threads to offload heavy vm operations
56 // like scavenge, garbage_collect etc.
57 //
58 
59 class VMThread: public NamedThread {
60  private:
61   static ThreadPriority _current_priority;
62 
63   static bool _should_terminate;
64   static bool _terminated;
65   static Monitor * _terminate_lock;
66   static PerfCounter* _perf_accumulated_vm_operation_time;
67 
68   static VMOperationTimeoutTask* _timeout_task;
69 
70   static bool handshake_alot();
71   static void setup_periodic_safepoint_if_needed();
72 
73   void evaluate_operation(VM_Operation* op);
74   void inner_execute(VM_Operation* op);
75   void wait_for_operation();
76 
77  public:
78   // Constructor
79   VMThread();
80 
81   // No destruction allowed
~VMThread()82   ~VMThread() {
83     guarantee(false, "VMThread deletion must fix the race with VM termination");
84   }
85 
86 
87   // Tester
is_VM_thread() const88   bool is_VM_thread() const                      { return true; }
89 
90   // The ever running loop for the VMThread
91   void loop();
92 
93   // Called to stop the VM thread
94   static void wait_for_vm_thread_exit();
should_terminate()95   static bool should_terminate()                  { return _should_terminate; }
is_terminated()96   static bool is_terminated()                     { return _terminated == true; }
97 
98   // Execution of vm operation
99   static void execute(VM_Operation* op);
100 
101   // Returns the current vm operation if any.
vm_operation()102   static VM_Operation* vm_operation()             {
103     assert(Thread::current()->is_VM_thread(), "Must be");
104     return _cur_vm_operation;
105   }
106 
vm_op_type()107   static VM_Operation::VMOp_Type vm_op_type()     {
108     VM_Operation* op = vm_operation();
109     assert(op != NULL, "sanity");
110     return op->type();
111   }
112 
113   // Returns the single instance of VMThread.
vm_thread()114   static VMThread* vm_thread()                    { return _vm_thread; }
115 
116   void verify();
117 
118   // Performance measurement
perf_accumulated_vm_operation_time()119   static PerfCounter* perf_accumulated_vm_operation_time() {
120     return _perf_accumulated_vm_operation_time;
121   }
122 
123   // Entry for starting vm thread
124   virtual void run();
125 
126   // Creations/Destructions
127   static void create();
128   static void destroy();
129 
130   static void wait_until_executed(VM_Operation* op);
131 
132  private:
133   // VM_Operation support
134   static VM_Operation*     _cur_vm_operation;   // Current VM operation
135   static VM_Operation*     _next_vm_operation;  // Next VM operation
136 
137   bool set_next_operation(VM_Operation *op);    // Set the _next_vm_operation if possible.
138 
139   // Pointer to single-instance of VM thread
140   static VMThread*     _vm_thread;
141 };
142 
143 #endif // SHARE_RUNTIME_VMTHREAD_HPP
144