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1 /*
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2 * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // Should this header be preserved during GC?
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26 inline bool markOopDesc::must_be_preserved_with_bias(oop obj_containing_mark) const {
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27 assert(UseBiasedLocking, "unexpected");
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28 if (has_bias_pattern()) {
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29 // Will reset bias at end of collection
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30 // Mark words of biased and currently locked objects are preserved separately
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31 return false;
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32 }
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33 markOop prototype_header = prototype_for_object(obj_containing_mark);
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34 if (prototype_header->has_bias_pattern()) {
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35 // Individual instance which has its bias revoked; must return
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36 // true for correctness
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37 return true;
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38 }
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39 return (!is_unlocked() || !has_no_hash());
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40 }
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41
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42 // Should this header (including its age bits) be preserved in the
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43 // case of a promotion failure during scavenge?
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44 inline bool markOopDesc::must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const {
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45 assert(UseBiasedLocking, "unexpected");
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46 // We don't explicitly save off the mark words of biased and
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47 // currently-locked objects during scavenges, so if during a
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48 // promotion failure we encounter either a biased mark word or a
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49 // klass which still has a biasable prototype header, we have to
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50 // preserve the mark word. This results in oversaving, but promotion
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51 // failures are rare, and this avoids adding more complex logic to
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52 // the scavengers to call new variants of
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53 // BiasedLocking::preserve_marks() / restore_marks() in the middle
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54 // of a scavenge when a promotion failure has first been detected.
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55 if (has_bias_pattern() ||
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56 prototype_for_object(obj_containing_mark)->has_bias_pattern()) {
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57 return true;
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58 }
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59 return (this != prototype());
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60 }
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61
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62 // Should this header (including its age bits) be preserved in the
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63 // case of a scavenge in which CMS is the old generation?
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64 inline bool markOopDesc::must_be_preserved_with_bias_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const {
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65 assert(UseBiasedLocking, "unexpected");
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66 // CMS scavenges preserve mark words in similar fashion to promotion failures; see above
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67 if (has_bias_pattern() ||
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68 klass_of_obj_containing_mark->klass_part()->prototype_header()->has_bias_pattern()) {
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69 return true;
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70 }
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71 return (this != prototype());
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72 }
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73
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74 inline markOop markOopDesc::prototype_for_object(oop obj) {
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75 #ifdef ASSERT
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76 markOop prototype_header = obj->klass()->klass_part()->prototype_header();
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77 assert(prototype_header == prototype() || prototype_header->has_bias_pattern(), "corrupt prototype header");
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78 #endif
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79 return obj->klass()->klass_part()->prototype_header();
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80 }
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