src/hotspot/share/runtime/handshake.cpp

rev 50557 : [mq]: 8204166

@@ -26,10 +26,11 @@
 #include "logging/log.hpp"
 #include "logging/logStream.hpp"
 #include "memory/resourceArea.hpp"
 #include "runtime/handshake.hpp"
 #include "runtime/interfaceSupport.inline.hpp"
+#include "runtime/orderAccess.hpp"
 #include "runtime/osThread.hpp"
 #include "runtime/semaphore.inline.hpp"
 #include "runtime/task.hpp"
 #include "runtime/timerTrace.hpp"
 #include "runtime/thread.hpp"

@@ -42,30 +43,38 @@
   virtual void do_handshake(JavaThread* thread) = 0;
   virtual void cancel_handshake(JavaThread* thread) = 0;
 };
 
 class HandshakeThreadsOperation: public HandshakeOperation {
-  Semaphore _done;
+  static Semaphore _done;
   ThreadClosure* _thread_cl;
 
 public:
-  HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {}
+  HandshakeThreadsOperation(ThreadClosure* cl) : _thread_cl(cl) {}
   void do_handshake(JavaThread* thread);
   void cancel_handshake(JavaThread* thread) { _done.signal(); };
 
   bool thread_has_completed() { return _done.trywait(); }
+
+#ifdef ASSERT
+  void check_state() {
+    assert(!_done.trywait(), "Must be zero");
+  }
+#endif
 };
 
+Semaphore HandshakeThreadsOperation::_done(0);
+
 class VM_Handshake: public VM_Operation {
-  HandshakeThreadsOperation* const _op;
   const jlong _handshake_timeout;
  public:
   bool evaluate_at_safepoint() const { return false; }
 
   bool evaluate_concurrently() const { return false; }
 
  protected:
+  HandshakeThreadsOperation* const _op;
 
   VM_Handshake(HandshakeThreadsOperation* op) :
       _op(op),
       _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {}
 

@@ -100,19 +109,19 @@
   }
   log_stream.flush();
   fatal("Handshake operation timed out");
 }
 
-
 class VM_HandshakeOneThread: public VM_Handshake {
   JavaThread* _target;
   bool _thread_alive;
  public:
   VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) :
     VM_Handshake(op), _target(target), _thread_alive(false) {}
 
   void doit() {
+    DEBUG_ONLY(_op->check_state();)
     TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
 
     {
       ThreadsListHandle tlh;
       if (tlh.includes(_target)) {

@@ -153,10 +162,11 @@
         // it has been removed from the ThreadsList. So we should just keep
         // looping here until while below returns false. If we have a bug,
         // then we hang here, which is good for debugging.
       }
     } while (!poll_for_completed_thread());
+    DEBUG_ONLY(_op->check_state();)
   }
 
   VMOp_Type type() const { return VMOp_HandshakeOneThread; }
 
   bool thread_alive() const { return _thread_alive; }

@@ -165,10 +175,11 @@
 class VM_HandshakeAllThreads: public VM_Handshake {
  public:
   VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
 
   void doit() {
+    DEBUG_ONLY(_op->check_state();)
     TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
 
     int number_of_threads_issued = 0;
     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) {
       set_handshake(thr);

@@ -211,11 +222,13 @@
       while (poll_for_completed_thread()) {
         // Includes canceled operations by exiting threads.
         number_of_threads_completed++;
       }
 
-    } while (number_of_threads_issued != number_of_threads_completed);
+    } while (number_of_threads_issued > number_of_threads_completed);
+    assert(number_of_threads_issued == number_of_threads_completed, "Must be the same");
+    DEBUG_ONLY(_op->check_state();)
   }
 
   VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
 };
 

@@ -243,12 +256,10 @@
 
   VMOp_Type type() const { return VMOp_HandshakeFallback; }
   bool thread_alive() const { return _thread_alive; }
 };
 
-#undef ALL_JAVA_THREADS
-
 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) {
   ResourceMark rm;
   FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s",
                                p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()));
   TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task));

@@ -280,11 +291,11 @@
     VMThread::execute(&op);
     return op.thread_alive();
   }
 }
 
-HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {}
+HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _thread_in_process_handshake(false) {}
 
 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) {
   _operation = op;
   SafepointMechanism::arm_local_poll(target);
 }

@@ -294,34 +305,35 @@
   SafepointMechanism::disarm_local_poll(target);
 }
 
 void HandshakeState::process_self_inner(JavaThread* thread) {
   assert(Thread::current() == thread, "should call from thread");
+
+  // If thread is not on threads list but armed, we cancel.
+  if (thread->is_terminated() && thread->has_handshake()) {
+    assert(false, "Should not happen");
+    thread->cancel_handshake();
+    return;
+  }
+
   CautiouslyPreserveExceptionMark pem(thread);
   ThreadInVMForHandshake tivm(thread);
   if (!_semaphore.trywait()) {
     _semaphore.wait_with_safepoint_check(thread);
   }
-  if (has_operation()) {
-    HandshakeOperation* op = _operation;
-    clear_handshake(thread);
+  HandshakeOperation* op = OrderAccess::load_acquire(&_operation);
     if (op != NULL) {
+    // Disarm before execute the operation
+    clear_handshake(thread);
       op->do_handshake(thread);
     }
-  }
   _semaphore.signal();
 }
 
 void HandshakeState::cancel_inner(JavaThread* thread) {
   assert(Thread::current() == thread, "should call from thread");
   assert(thread->thread_state() == _thread_in_vm, "must be in vm state");
-#ifdef DEBUG
-  {
-    ThreadsListHandle tlh;
-    assert(!tlh.includes(_target), "java thread must not be on threads list");
-  }
-#endif
   HandshakeOperation* op = _operation;
   clear_handshake(thread);
   if (op != NULL) {
     op->cancel_handshake(thread);
   }

@@ -330,18 +342,18 @@
 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) {
   return SafepointSynchronize::safepoint_safe(target, target->thread_state());
 }
 
 bool HandshakeState::claim_handshake_for_vmthread() {
-  if (_semaphore.trywait()) {
-    if (has_operation()) {
-      _vmthread_holds_semaphore = true;
-    } else {
-      _semaphore.signal();
+  if (!_semaphore.trywait()) {
+    return false;
     }
+  if (has_operation()) {
+    return true;
   }
-  return _vmthread_holds_semaphore;
+  _semaphore.signal();
+  return false;
 }
 
 void HandshakeState::process_by_vmthread(JavaThread* target) {
   assert(Thread::current()->is_VM_thread(), "should call from vm thread");
 

@@ -356,15 +368,19 @@
   }
 
   // If we own the semaphore at this point and while owning the semaphore
   // can observe a safe state the thread cannot possibly continue without
   // getting caught by the semaphore.
-  if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) {
+  if (claim_handshake_for_vmthread()) {
+    if(!vmthread_can_process_handshake(target)) {
+      _semaphore.signal();
+      return;
+    }
     guarantee(!_semaphore.trywait(), "we should already own the semaphore");
 
     _operation->do_handshake(target);
+    // Disarm after VM thread have executed the operation.
     clear_handshake(target);
-    _vmthread_holds_semaphore = false;
     // Release the thread
     _semaphore.signal();
   }
 }