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 
  36 MetadataOnStackBuffer* MetadataOnStackMark::_used_buffers = NULL;
  37 MetadataOnStackBuffer* MetadataOnStackMark::_free_buffers = NULL;
  38 
  39 MetadataOnStackBuffer* MetadataOnStackMark::_current_buffer = NULL;
  40 NOT_PRODUCT(bool MetadataOnStackMark::_is_active = false;)
  41 
  42 // Walk metadata on the stack and mark it so that redefinition doesn't delete
  43 // it.  Class unloading only deletes in-error class files, methods created by
  44 // the relocator and dummy constant pools.  None of these appear anywhere except
  45 // in metadata Handles.
  46 MetadataOnStackMark::MetadataOnStackMark(bool redefinition_walk) {
  47   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
  48   assert(_used_buffers == NULL, "sanity check");
  49   assert(!_is_active, "MetadataOnStackMarks do not nest");
  50   NOT_PRODUCT(_is_active = true;)
  51 
  52   Threads::metadata_handles_do(Metadata::mark_on_stack);
  53 
  54   if (redefinition_walk) {
  55     Threads::metadata_do(Metadata::mark_on_stack);
  56     CodeCache::alive_nmethods_do(nmethod::mark_on_stack);
  57     CompileBroker::mark_on_stack();
  58     JvmtiCurrentBreakpoints::metadata_do(Metadata::mark_on_stack);
  59     ThreadService::metadata_do(Metadata::mark_on_stack);
  60   }
  61 }
  62 
  63 MetadataOnStackMark::~MetadataOnStackMark() {
  64   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
  65   // Unmark everything that was marked.   Can't do the same walk because
  66   // redefine classes messes up the code cache so the set of methods
  67   // might not be the same.
  68   retire_current_buffer();
  69 
  70   MetadataOnStackBuffer* buffer = _used_buffers;
  71   while (buffer != NULL) {
  72     // Clear on stack state for all metadata.
  73     size_t size = buffer->size();
  74     for (size_t i  = 0; i < size; i++) {
  75       Metadata* md = buffer->at(i);
  76       md->set_on_stack(false);
  77     }
  78 
  79     MetadataOnStackBuffer* next = buffer->next_used();
  80 
  81     // Move the buffer to the free list.
  82     buffer->clear();
  83     buffer->set_next_used(NULL);
  84     buffer->set_next_free(_free_buffers);
  85     _free_buffers = buffer;
  86 
  87     // Step to next used buffer.
  88     buffer = next;
  89   }
  90 
  91   _used_buffers = NULL;
  92 
  93   NOT_PRODUCT(_is_active = false;)
  94 }
  95 
  96 void MetadataOnStackMark::retire_buffer(MetadataOnStackBuffer* buffer) {
  97   if (buffer == NULL) {
  98     return;
  99   }
 100   buffer->set_next_used(_used_buffers);
 101   _used_buffers = buffer;
 102 }
 103 
 104 // Current buffer is full or we're ready to walk them, add it to the used list.
 105 void MetadataOnStackMark::retire_current_buffer() {
 106   retire_buffer(_current_buffer);
 107   _current_buffer = NULL;
 108 }
 109 
 110 // Get buffer off free list.
 111 MetadataOnStackBuffer* MetadataOnStackMark::allocate_buffer() {
 112   MetadataOnStackBuffer* allocated = _free_buffers;
 113 
 114   if (allocated != NULL) {
 115     _free_buffers = allocated->next_free();
 116   }
 117 
 118   if (allocated == NULL) {
 119     allocated = new MetadataOnStackBuffer();
 120   }
 121 
 122   assert(!allocated->is_full(), "Should not be full: " PTR_FORMAT, p2i(allocated));
 123 
 124   return allocated;
 125 }
 126 
 127 // Record which objects are marked so we can unmark the same objects.
 128 void MetadataOnStackMark::record(Metadata* m) {
 129   assert(_is_active, "metadata on stack marking is active");
 130 
 131   MetadataOnStackBuffer* buffer = _current_buffer;
 132 
 133   if (buffer != NULL && buffer->is_full()) {
 134     retire_buffer(buffer);
 135     buffer = NULL;
 136   }
 137 
 138   if (buffer == NULL) {
 139     buffer = allocate_buffer();
 140     _current_buffer = buffer;
 141   }
 142 
 143   buffer->push(m);
 144 }