1 /*
   2  * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "code/codeCache.hpp"
  28 #include "compiler/compileBroker.hpp"
  29 #include "oops/metadata.hpp"
  30 #include "prims/jvmtiImpl.hpp"
  31 #include "runtime/synchronizer.hpp"
  32 #include "runtime/thread.hpp"
  33 #include "services/threadService.hpp"
  34 #include "utilities/chunkedList.hpp"
  35 #if INCLUDE_JVMCI
  36 #include "jvmci/jvmciRuntime.hpp"
  37 #endif
  38 
  39 MetadataOnStackBuffer* MetadataOnStackMark::_used_buffers = NULL;
  40 MetadataOnStackBuffer* MetadataOnStackMark::_free_buffers = NULL;
  41 
  42 MetadataOnStackBuffer* MetadataOnStackMark::_current_buffer = NULL;
  43 NOT_PRODUCT(bool MetadataOnStackMark::_is_active = false;)
  44 
  45 // Walk metadata on the stack and mark it so that redefinition doesn't delete
  46 // it.  Class unloading only deletes in-error class files, methods created by
  47 // the relocator and dummy constant pools.  None of these appear anywhere except
  48 // in metadata Handles.
  49 MetadataOnStackMark::MetadataOnStackMark(bool redefinition_walk) {
  50   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
  51   assert(_used_buffers == NULL, "sanity check");
  52   assert(!_is_active, "MetadataOnStackMarks do not nest");
  53   NOT_PRODUCT(_is_active = true;)
  54 
  55   Threads::metadata_handles_do(Metadata::mark_on_stack);
  56 
  57   if (redefinition_walk) {
  58     Threads::metadata_do(Metadata::mark_on_stack);
  59     CodeCache::alive_nmethods_do(nmethod::mark_on_stack);
  60     CompileBroker::mark_on_stack();
  61     JvmtiCurrentBreakpoints::metadata_do(Metadata::mark_on_stack);
  62     ThreadService::metadata_do(Metadata::mark_on_stack);
  63 #if INCLUDE_JVMCI
  64     JVMCIRuntime::metadata_do(Metadata::mark_on_stack);
  65 #endif
  66   }
  67 }
  68 
  69 MetadataOnStackMark::~MetadataOnStackMark() {
  70   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
  71   // Unmark everything that was marked.   Can't do the same walk because
  72   // redefine classes messes up the code cache so the set of methods
  73   // might not be the same.
  74   retire_current_buffer();
  75 
  76   MetadataOnStackBuffer* buffer = _used_buffers;
  77   while (buffer != NULL) {
  78     // Clear on stack state for all metadata.
  79     size_t size = buffer->size();
  80     for (size_t i  = 0; i < size; i++) {
  81       Metadata* md = buffer->at(i);
  82       md->set_on_stack(false);
  83     }
  84 
  85     MetadataOnStackBuffer* next = buffer->next_used();
  86 
  87     // Move the buffer to the free list.
  88     buffer->clear();
  89     buffer->set_next_used(NULL);
  90     buffer->set_next_free(_free_buffers);
  91     _free_buffers = buffer;
  92 
  93     // Step to next used buffer.
  94     buffer = next;
  95   }
  96 
  97   _used_buffers = NULL;
  98 
  99   NOT_PRODUCT(_is_active = false;)
 100 }
 101 
 102 void MetadataOnStackMark::retire_buffer(MetadataOnStackBuffer* buffer) {
 103   if (buffer == NULL) {
 104     return;
 105   }
 106   buffer->set_next_used(_used_buffers);
 107   _used_buffers = buffer;
 108 }
 109 
 110 // Current buffer is full or we're ready to walk them, add it to the used list.
 111 void MetadataOnStackMark::retire_current_buffer() {
 112   retire_buffer(_current_buffer);
 113   _current_buffer = NULL;
 114 }
 115 
 116 // Get buffer off free list.
 117 MetadataOnStackBuffer* MetadataOnStackMark::allocate_buffer() {
 118   MetadataOnStackBuffer* allocated = _free_buffers;
 119 
 120   if (allocated != NULL) {
 121     _free_buffers = allocated->next_free();
 122   }
 123 
 124   if (allocated == NULL) {
 125     allocated = new MetadataOnStackBuffer();
 126   }
 127 
 128   assert(!allocated->is_full(), err_msg("Should not be full: " PTR_FORMAT, p2i(allocated)));
 129 
 130   return allocated;
 131 }
 132 
 133 // Record which objects are marked so we can unmark the same objects.
 134 void MetadataOnStackMark::record(Metadata* m) {
 135   assert(_is_active, "metadata on stack marking is active");
 136 
 137   MetadataOnStackBuffer* buffer = _current_buffer;
 138 
 139   if (buffer != NULL && buffer->is_full()) {
 140     retire_buffer(buffer);
 141     buffer = NULL;
 142   }
 143 
 144   if (buffer == NULL) {
 145     buffer = allocate_buffer();
 146     _current_buffer = buffer;
 147   }
 148 
 149   buffer->push(m);
 150 }