1 /* 2 * Copyright (c) 2015, 2019, 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 #include "precompiled.hpp" 25 #include "gc/z/zBarrier.inline.hpp" 26 #include "gc/z/zHeap.inline.hpp" 27 #include "gc/z/zOop.inline.hpp" 28 #include "gc/z/zOopClosures.inline.hpp" 29 #include "memory/iterator.inline.hpp" 30 #include "oops/oop.inline.hpp" 31 #include "runtime/safepoint.hpp" 32 #include "utilities/debug.hpp" 33 34 bool ZBarrier::during_mark() { 35 return ZGlobalPhase == ZPhaseMark; 36 } 37 38 bool ZBarrier::during_relocate() { 39 return ZGlobalPhase == ZPhaseRelocate; 40 } 41 42 template <bool finalizable> 43 bool ZBarrier::should_mark_through(uintptr_t addr) { 44 // Finalizable marked oops can still exists on the heap after marking 45 // has completed, in which case we just want to convert this into a 46 // good oop and not push it on the mark stack. 47 if (!during_mark()) { 48 assert(ZAddress::is_marked(addr), "Should be marked"); 49 assert(ZAddress::is_finalizable(addr), "Should be finalizable"); 50 return false; 51 } 52 53 // During marking, we mark through already marked oops to avoid having 54 // some large part of the object graph hidden behind a pushed, but not 55 // yet flushed, entry on a mutator mark stack. Always marking through 56 // allows the GC workers to proceed through the object graph even if a 57 // mutator touched an oop first, which in turn will reduce the risk of 58 // having to flush mark stacks multiple times to terminate marking. 59 // 60 // However, when doing finalizable marking we don't always want to mark 61 // through. First, marking through an already strongly marked oop would 62 // be wasteful, since we will then proceed to do finalizable marking on 63 // an object which is, or will be, marked strongly. Second, marking 64 // through an already finalizable marked oop would also be wasteful, 65 // since such oops can never end up on a mutator mark stack and can 66 // therefore not hide some part of the object graph from GC workers. 67 if (finalizable) { 68 return !ZAddress::is_marked(addr); 69 } 70 71 // Mark through 72 return true; 73 } 74 75 template <bool finalizable, bool publish> 76 uintptr_t ZBarrier::mark(uintptr_t addr) { 77 uintptr_t good_addr; 78 79 if (ZAddress::is_marked(addr)) { 80 // Already marked, but try to mark though anyway 81 good_addr = ZAddress::good(addr); 82 } else if (ZAddress::is_remapped(addr)) { 83 // Already remapped, but also needs to be marked 84 good_addr = ZAddress::good(addr); 85 } else { 86 // Needs to be both remapped and marked 87 good_addr = remap(addr); 88 } 89 90 // Mark 91 if (should_mark_through<finalizable>(addr)) { 92 ZHeap::heap()->mark_object<finalizable, publish>(good_addr); 93 } 94 95 return good_addr; 96 } 97 98 uintptr_t ZBarrier::remap(uintptr_t addr) { 99 assert(!ZAddress::is_good(addr), "Should not be good"); 100 assert(!ZAddress::is_weak_good(addr), "Should not be weak good"); 101 return ZHeap::heap()->remap_object(addr); 102 } 103 104 uintptr_t ZBarrier::relocate(uintptr_t addr) { 105 assert(!ZAddress::is_good(addr), "Should not be good"); 106 assert(!ZAddress::is_weak_good(addr), "Should not be weak good"); 107 return ZHeap::heap()->relocate_object(addr); 108 } 109 110 uintptr_t ZBarrier::relocate_or_mark(uintptr_t addr) { 111 return during_relocate() ? relocate(addr) : mark<Strong, Publish>(addr); 112 } 113 114 uintptr_t ZBarrier::relocate_or_remap(uintptr_t addr) { 115 return during_relocate() ? relocate(addr) : remap(addr); 116 } 117 118 // 119 // Load barrier 120 // 121 uintptr_t ZBarrier::load_barrier_on_oop_slow_path(uintptr_t addr) { 122 return relocate_or_mark(addr); 123 } 124 125 void ZBarrier::load_barrier_on_oop_fields(oop o) { 126 assert(ZAddress::is_good(ZOop::to_address(o)), "Should be good"); 127 ZLoadBarrierOopClosure cl; 128 o->oop_iterate(&cl); 129 } 130 131 // 132 // Weak load barrier 133 // 134 uintptr_t ZBarrier::weak_load_barrier_on_oop_slow_path(uintptr_t addr) { 135 return ZAddress::is_weak_good(addr) ? ZAddress::good(addr) : relocate_or_remap(addr); 136 } 137 138 uintptr_t ZBarrier::weak_load_barrier_on_weak_oop_slow_path(uintptr_t addr) { 139 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr); 140 if (ZHeap::heap()->is_object_strongly_live(good_addr)) { 141 return good_addr; 142 } 143 144 // Not strongly live 145 return 0; 146 } 147 148 uintptr_t ZBarrier::weak_load_barrier_on_phantom_oop_slow_path(uintptr_t addr) { 149 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr); 150 if (ZHeap::heap()->is_object_live(good_addr)) { 151 return good_addr; 152 } 153 154 // Not live 155 return 0; 156 } 157 158 // 159 // Keep alive barrier 160 // 161 uintptr_t ZBarrier::keep_alive_barrier_on_weak_oop_slow_path(uintptr_t addr) { 162 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr); 163 assert(ZHeap::heap()->is_object_strongly_live(good_addr), "Should be live"); 164 return good_addr; 165 } 166 167 uintptr_t ZBarrier::keep_alive_barrier_on_phantom_oop_slow_path(uintptr_t addr) { 168 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr); 169 assert(ZHeap::heap()->is_object_live(good_addr), "Should be live"); 170 return good_addr; 171 } 172 173 // 174 // Mark barrier 175 // 176 uintptr_t ZBarrier::mark_barrier_on_oop_slow_path(uintptr_t addr) { 177 return mark<Strong, Overflow>(addr); 178 } 179 180 uintptr_t ZBarrier::mark_barrier_on_finalizable_oop_slow_path(uintptr_t addr) { 181 const uintptr_t good_addr = mark<Finalizable, Overflow>(addr); 182 if (ZAddress::is_good(addr)) { 183 // If the oop was already strongly marked/good, then we do 184 // not want to downgrade it to finalizable marked/good. 185 return good_addr; 186 } 187 188 // Make the oop finalizable marked/good, instead of normal marked/good. 189 // This is needed because an object might first becomes finalizable 190 // marked by the GC, and then loaded by a mutator thread. In this case, 191 // the mutator thread must be able to tell that the object needs to be 192 // strongly marked. The finalizable bit in the oop exists to make sure 193 // that a load of a finalizable marked oop will fall into the barrier 194 // slow path so that we can mark the object as strongly reachable. 195 return ZAddress::finalizable_good(good_addr); 196 } 197 198 uintptr_t ZBarrier::mark_barrier_on_root_oop_slow_path(uintptr_t addr) { 199 assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint"); 200 assert(during_mark(), "Invalid phase"); 201 202 // Mark 203 return mark<Strong, Publish>(addr); 204 } 205 206 // 207 // Relocate barrier 208 // 209 uintptr_t ZBarrier::relocate_barrier_on_root_oop_slow_path(uintptr_t addr) { 210 assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint"); 211 assert(during_relocate(), "Invalid phase"); 212 213 // Relocate 214 return relocate(addr); 215 } 216 217 // 218 // Narrow oop variants, never used. 219 // 220 oop ZBarrier::load_barrier_on_oop_field(volatile narrowOop* p) { 221 ShouldNotReachHere(); 222 return NULL; 223 } 224 225 oop ZBarrier::load_barrier_on_oop_field_preloaded(volatile narrowOop* p, oop o) { 226 ShouldNotReachHere(); 227 return NULL; 228 } 229 230 void ZBarrier::load_barrier_on_oop_array(volatile narrowOop* p, size_t length) { 231 ShouldNotReachHere(); 232 } 233 234 oop ZBarrier::load_barrier_on_weak_oop_field_preloaded(volatile narrowOop* p, oop o) { 235 ShouldNotReachHere(); 236 return NULL; 237 } 238 239 oop ZBarrier::load_barrier_on_phantom_oop_field_preloaded(volatile narrowOop* p, oop o) { 240 ShouldNotReachHere(); 241 return NULL; 242 } 243 244 oop ZBarrier::weak_load_barrier_on_oop_field_preloaded(volatile narrowOop* p, oop o) { 245 ShouldNotReachHere(); 246 return NULL; 247 } 248 249 oop ZBarrier::weak_load_barrier_on_weak_oop_field_preloaded(volatile narrowOop* p, oop o) { 250 ShouldNotReachHere(); 251 return NULL; 252 } 253 254 oop ZBarrier::weak_load_barrier_on_phantom_oop_field_preloaded(volatile narrowOop* p, oop o) { 255 ShouldNotReachHere(); 256 return NULL; 257 }