8139595: MethodHandles::remove_dependent_nmethod is not MT safe

Reviewed-by: jrose, coleenp

hotspot/src/share/vm/code/dependencyContext.cpp

@@ -0,0 +1,347 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "code/nmethod.hpp"
+#include "code/dependencies.hpp"
+#include "code/dependencyContext.hpp"
+#include "memory/resourceArea.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/perfData.hpp"
+#include "utilities/exceptions.hpp"
+
+PerfCounter* DependencyContext::_perf_total_buckets_allocated_count   = NULL;
+PerfCounter* DependencyContext::_perf_total_buckets_deallocated_count = NULL;
+PerfCounter* DependencyContext::_perf_total_buckets_stale_count       = NULL;
+PerfCounter* DependencyContext::_perf_total_buckets_stale_acc_count   = NULL;
+
+void dependencyContext_init() {
+  DependencyContext::init();
+}
+
+void DependencyContext::init() {
+  if (UsePerfData) {
+    EXCEPTION_MARK;
+    _perf_total_buckets_allocated_count =
+        PerfDataManager::create_counter(SUN_CI, "nmethodBucketsAllocated", PerfData::U_Events, CHECK);
+    _perf_total_buckets_deallocated_count =
+        PerfDataManager::create_counter(SUN_CI, "nmethodBucketsDeallocated", PerfData::U_Events, CHECK);
+    _perf_total_buckets_stale_count =
+        PerfDataManager::create_counter(SUN_CI, "nmethodBucketsStale", PerfData::U_Events, CHECK);
+    _perf_total_buckets_stale_acc_count =
+        PerfDataManager::create_counter(SUN_CI, "nmethodBucketsStaleAccumulated", PerfData::U_Events, CHECK);
+  }
+}
+
+//
+// Walk the list of dependent nmethods searching for nmethods which
+// are dependent on the changes that were passed in and mark them for
+// deoptimization.  Returns the number of nmethods found.
+//
+int DependencyContext::mark_dependent_nmethods(DepChange& changes) {
+  int found = 0;
+  for (nmethodBucket* b = dependencies(); b != NULL; b = b->next()) {
+    nmethod* nm = b->get_nmethod();
+    // since dependencies aren't removed until an nmethod becomes a zombie,
+    // the dependency list may contain nmethods which aren't alive.
+    if (b->count() > 0 && nm->is_alive() && !nm->is_marked_for_deoptimization() && nm->check_dependency_on(changes)) {
+      if (TraceDependencies) {
+        ResourceMark rm;
+        tty->print_cr("Marked for deoptimization");
+        changes.print();
+        nm->print();
+        nm->print_dependencies();
+      }
+      nm->mark_for_deoptimization();
+      found++;
+    }
+  }
+  return found;
+}
+
+//
+// Add an nmethod to the dependency context.
+// It's possible that an nmethod has multiple dependencies on a klass
+// so a count is kept for each bucket to guarantee that creation and
+// deletion of dependencies is consistent.
+//
+void DependencyContext::add_dependent_nmethod(nmethod* nm, bool expunge) {
+  assert_lock_strong(CodeCache_lock);
+  for (nmethodBucket* b = dependencies(); b != NULL; b = b->next()) {
+    if (nm == b->get_nmethod()) {
+      b->increment();
+      return;
+    }
+  }
+  set_dependencies(new nmethodBucket(nm, dependencies()));
+  if (UsePerfData) {
+    _perf_total_buckets_allocated_count->inc();
+  }
+  if (expunge) {
+    // Remove stale entries from the list.
+    expunge_stale_entries();
+  }
+}
+
+//
+// Remove an nmethod dependency from the context.
+// Decrement count of the nmethod in the dependency list and, optionally, remove
+// the bucket completely when the count goes to 0.  This method must find
+// a corresponding bucket otherwise there's a bug in the recording of dependencies.
+// Can be called concurrently by parallel GC threads.
+//
+void DependencyContext::remove_dependent_nmethod(nmethod* nm, bool expunge) {
+  assert_locked_or_safepoint(CodeCache_lock);
+  nmethodBucket* first = dependencies();
+  nmethodBucket* last = NULL;
+  for (nmethodBucket* b = first; b != NULL; b = b->next()) {
+    if (nm == b->get_nmethod()) {
+      int val = b->decrement();
+      guarantee(val >= 0, "Underflow: %d", val);
+      if (val == 0) {
+        if (expunge) {
+          if (last == NULL) {
+            set_dependencies(b->next());
+          } else {
+            last->set_next(b->next());
+          }
+          delete b;
+          if (UsePerfData) {
+            _perf_total_buckets_deallocated_count->inc();
+          }
+        } else {
+          // Mark the context as having stale entries, since it is not safe to
+          // expunge the list right now.
+          set_has_stale_entries(true);
+          if (UsePerfData) {
+            _perf_total_buckets_stale_count->inc();
+            _perf_total_buckets_stale_acc_count->inc();
+          }
+        }
+      }
+      if (expunge) {
+        // Remove stale entries from the list.
+        expunge_stale_entries();
+      }
+      return;
+    }
+    last = b;
+  }
+#ifdef ASSERT
+  tty->print_raw_cr("### can't find dependent nmethod");
+  nm->print();
+#endif // ASSERT
+  ShouldNotReachHere();
+}
+
+//
+// Reclaim all unused buckets.
+//
+void DependencyContext::expunge_stale_entries() {
+  assert_locked_or_safepoint(CodeCache_lock);
+  if (!has_stale_entries()) {
+    assert(!find_stale_entries(), "inconsistent info");
+    return;
+  }
+  nmethodBucket* first = dependencies();
+  nmethodBucket* last = NULL;
+  int removed = 0;
+  for (nmethodBucket* b = first; b != NULL;) {
+    assert(b->count() >= 0, "bucket count: %d", b->count());
+    nmethodBucket* next = b->next();
+    if (b->count() == 0) {
+      if (last == NULL) {
+        first = next;
+      } else {
+        last->set_next(next);
+      }
+      removed++;
+      delete b;
+      // last stays the same.
+    } else {
+      last = b;
+    }
+    b = next;
+  }
+  set_dependencies(first);
+  set_has_stale_entries(false);
+  if (UsePerfData && removed > 0) {
+    _perf_total_buckets_deallocated_count->inc(removed);
+    _perf_total_buckets_stale_count->dec(removed);
+  }
+}
+
+//
+// Invalidate all dependencies in the context
+int DependencyContext::remove_all_dependents() {
+  assert_locked_or_safepoint(CodeCache_lock);
+  nmethodBucket* b = dependencies();
+  set_dependencies(NULL);
+  int marked = 0;
+  int removed = 0;
+  while (b != NULL) {
+    nmethod* nm = b->get_nmethod();
+    if (b->count() > 0 && nm->is_alive() && !nm->is_marked_for_deoptimization()) {
+      nm->mark_for_deoptimization();
+      marked++;
+    }
+    nmethodBucket* next = b->next();
+    removed++;
+    delete b;
+    b = next;
+  }
+  set_has_stale_entries(false);
+  if (UsePerfData && removed > 0) {
+    _perf_total_buckets_deallocated_count->inc(removed);
+  }
+  return marked;
+}
+
+#ifndef PRODUCT
+void DependencyContext::print_dependent_nmethods(bool verbose) {
+  int idx = 0;
+  for (nmethodBucket* b = dependencies(); b != NULL; b = b->next()) {
+    nmethod* nm = b->get_nmethod();
+    tty->print("[%d] count=%d { ", idx++, b->count());
+    if (!verbose) {
+      nm->print_on(tty, "nmethod");
+      tty->print_cr(" } ");
+    } else {
+      nm->print();
+      nm->print_dependencies();
+      tty->print_cr("--- } ");
+    }
+  }
+}
+
+bool DependencyContext::is_dependent_nmethod(nmethod* nm) {
+  for (nmethodBucket* b = dependencies(); b != NULL; b = b->next()) {
+    if (nm == b->get_nmethod()) {
+#ifdef ASSERT
+      int count = b->count();
+      assert(count >= 0, "count shouldn't be negative: %d", count);
+#endif
+      return true;
+    }
+  }
+  return false;
+}
+
+bool DependencyContext::find_stale_entries() {
+  for (nmethodBucket* b = dependencies(); b != NULL; b = b->next()) {
+    if (b->count() == 0)  return true;
+  }
+  return false;
+}
+
+#endif //PRODUCT
+
+int nmethodBucket::decrement() {
+  return Atomic::add(-1, (volatile int *)&_count);
+}
+
+/////////////// Unit tests ///////////////
+
+#ifndef PRODUCT
+
+class TestDependencyContext {
+ public:
+  nmethod* _nmethods[3];
+
+  intptr_t _dependency_context;
+
+  TestDependencyContext() : _dependency_context(DependencyContext::EMPTY) {
+    CodeCache_lock->lock_without_safepoint_check();
+
+    DependencyContext depContext(&_dependency_context);
+
+    _nmethods[0] = reinterpret_cast<nmethod*>(0x8 * 0);
+    _nmethods[1] = reinterpret_cast<nmethod*>(0x8 * 1);
+    _nmethods[2] = reinterpret_cast<nmethod*>(0x8 * 2);
+
+    depContext.add_dependent_nmethod(_nmethods[2]);
+    depContext.add_dependent_nmethod(_nmethods[1]);
+    depContext.add_dependent_nmethod(_nmethods[0]);
+  }
+
+  ~TestDependencyContext() {
+    wipe();
+    CodeCache_lock->unlock();
+  }
+
+  static void testRemoveDependentNmethod(int id, bool delete_immediately) {
+    TestDependencyContext c;
+    DependencyContext depContext(&c._dependency_context);
+    assert(!has_stale_entries(depContext), "check");
+
+    nmethod* nm = c._nmethods[id];
+    depContext.remove_dependent_nmethod(nm, delete_immediately);
+
+    if (!delete_immediately) {
+      assert(has_stale_entries(depContext), "check");
+      assert(depContext.is_dependent_nmethod(nm), "check");
+      depContext.expunge_stale_entries();
+    }
+
+    assert(!has_stale_entries(depContext), "check");
+    assert(!depContext.is_dependent_nmethod(nm), "check");
+  }
+
+  static void testRemoveDependentNmethod() {
+    testRemoveDependentNmethod(0, false);
+    testRemoveDependentNmethod(1, false);
+    testRemoveDependentNmethod(2, false);
+
+    testRemoveDependentNmethod(0, true);
+    testRemoveDependentNmethod(1, true);
+    testRemoveDependentNmethod(2, true);
+  }
+
+  static void test() {
+    testRemoveDependentNmethod();
+  }
+
+  static bool has_stale_entries(DependencyContext ctx) {
+    assert(ctx.has_stale_entries() == ctx.find_stale_entries(), "check");
+    return ctx.has_stale_entries();
+  }
+
+  void wipe() {
+    DependencyContext ctx(&_dependency_context);
+    nmethodBucket* b = ctx.dependencies();
+    ctx.set_dependencies(NULL);
+    ctx.set_has_stale_entries(false);
+    while (b != NULL) {
+      nmethodBucket* next = b->next();
+      delete b;
+      b = next;
+    }
+  }
+};
+
+void TestDependencyContext_test() {
+  TestDependencyContext::test();
+}
+
+#endif // PRODUCT