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hotspot/src/share/vm/memory/gcLocker.cpp

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+/*
+ * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_gcLocker.cpp.incl"
+
+volatile jint GC_locker::_jni_lock_count = 0;
+volatile jint GC_locker::_lock_count     = 0;
+volatile bool GC_locker::_needs_gc       = false;
+volatile bool GC_locker::_doing_gc       = false;
+
+void GC_locker::stall_until_clear() {
+  assert(!JavaThread::current()->in_critical(), "Would deadlock");
+  MutexLocker   ml(JNICritical_lock);
+  // Wait for _needs_gc  to be cleared
+  while (GC_locker::needs_gc()) {
+    JNICritical_lock->wait();
+  }
+}
+
+void GC_locker::jni_lock_slow() {
+  MutexLocker mu(JNICritical_lock);
+  // Block entering threads if we know at least one thread is in a
+  // JNI critical region and we need a GC.
+  // We check that at least one thread is in a critical region before
+  // blocking because blocked threads are woken up by a thread exiting
+  // a JNI critical region.
+  while ((is_jni_active() && needs_gc()) || _doing_gc) {
+    JNICritical_lock->wait();
+  }
+  jni_lock();
+}
+
+void GC_locker::jni_unlock_slow() {
+  MutexLocker mu(JNICritical_lock);
+  jni_unlock();
+  if (needs_gc() && !is_jni_active()) {
+    // We're the last thread out. Cause a GC to occur.
+    // GC will also check is_active, so this check is not
+    // strictly needed. It's added here to make it clear that
+    // the GC will NOT be performed if any other caller
+    // of GC_locker::lock() still needs GC locked.
+    if (!is_active()) {
+      _doing_gc = true;
+      {
+        // Must give up the lock while at a safepoint
+        MutexUnlocker munlock(JNICritical_lock);
+        Universe::heap()->collect(GCCause::_gc_locker);
+      }
+      _doing_gc = false;
+    }
+    clear_needs_gc();
+    JNICritical_lock->notify_all();
+  }
+}
+
+// Implementation of No_GC_Verifier
+
+#ifdef ASSERT
+
+No_GC_Verifier::No_GC_Verifier(bool verifygc) {
+  _verifygc = verifygc;
+  if (_verifygc) {
+    CollectedHeap* h = Universe::heap();
+    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
+    _old_invocations = h->total_collections();
+  }
+}
+
+
+No_GC_Verifier::~No_GC_Verifier() {
+  if (_verifygc) {
+    CollectedHeap* h = Universe::heap();
+    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
+    if (_old_invocations != h->total_collections()) {
+      fatal("collection in a No_GC_Verifier secured function");
+    }
+  }
+}
+
+Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {
+  _ngcv = ngcv;
+  if (_ngcv->_verifygc) {
+    // if we were verifying, then make sure that nothing is
+    // wrong before we "pause" verification
+    CollectedHeap* h = Universe::heap();
+    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
+    if (_ngcv->_old_invocations != h->total_collections()) {
+      fatal("collection in a No_GC_Verifier secured function");
+    }
+  }
+}
+
+
+Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {
+  if (_ngcv->_verifygc) {
+    // if we were verifying before, then reenable verification
+    CollectedHeap* h = Universe::heap();
+    assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
+    _ngcv->_old_invocations = h->total_collections();
+  }
+}
+
+
+// JRT_LEAF rules:
+// A JRT_LEAF method may not interfere with safepointing by
+//   1) acquiring or blocking on a Mutex or JavaLock - checked
+//   2) allocating heap memory - checked
+//   3) executing a VM operation - checked
+//   4) executing a system call (including malloc) that could block or grab a lock
+//   5) invoking GC
+//   6) reaching a safepoint
+//   7) running too long
+// Nor may any method it calls.
+JRT_Leaf_Verifier::JRT_Leaf_Verifier()
+  : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())
+{
+}
+
+JRT_Leaf_Verifier::~JRT_Leaf_Verifier()
+{
+}
+
+bool JRT_Leaf_Verifier::should_verify_GC() {
+  switch (JavaThread::current()->thread_state()) {
+  case _thread_in_Java:
+    // is in a leaf routine, there must be no safepoint.
+    return true;
+  case _thread_in_native:
+    // A native thread is not subject to safepoints.
+    // Even while it is in a leaf routine, GC is ok
+    return false;
+  default:
+    // Leaf routines cannot be called from other contexts.
+    ShouldNotReachHere();
+    return false;
+  }
+}
+#endif