1 /* 2 * Copyright (c) 2015, 2017, 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 #ifndef SHARE_GC_Z_ZBARRIER_INLINE_HPP 25 #define SHARE_GC_Z_ZBARRIER_INLINE_HPP 26 27 #include "gc/z/zAddress.inline.hpp" 28 #include "gc/z/zBarrier.hpp" 29 #include "gc/z/zOop.inline.hpp" 30 #include "gc/z/zResurrection.inline.hpp" 31 #include "runtime/atomic.hpp" 32 33 template <ZBarrierFastPath fast_path, ZBarrierSlowPath slow_path> 34 inline oop ZBarrier::barrier(volatile oop* p, oop o) { 35 uintptr_t addr = ZOop::to_address(o); 36 37 retry: 38 // Fast path 39 if (fast_path(addr)) { 40 return ZOop::to_oop(addr); 41 } 42 43 // Slow path 44 const uintptr_t good_addr = slow_path(addr); 45 46 // Self heal, but only if the address was actually updated by the slow path, 47 // which might not be the case, e.g. when marking through an already good oop. 48 if (p != NULL && good_addr != addr) { 49 const uintptr_t prev_addr = Atomic::cmpxchg(good_addr, (volatile uintptr_t*)p, addr); 50 if (prev_addr != addr) { 51 // Some other thread overwrote the oop. If this oop was updated by a 52 // weak barrier the new oop might not be good, in which case we need 53 // to re-apply this barrier. 54 addr = prev_addr; 55 goto retry; 56 } 57 } 58 59 return ZOop::to_oop(good_addr); 60 } 61 62 template <ZBarrierFastPath fast_path, ZBarrierSlowPath slow_path> 63 inline oop ZBarrier::weak_barrier(volatile oop* p, oop o) { 64 const uintptr_t addr = ZOop::to_address(o); 65 66 // Fast path 67 if (fast_path(addr)) { 68 // Return the good address instead of the weak good address 69 // to ensure that the currently active heap view is used. 70 return ZOop::to_oop(ZAddress::good_or_null(addr)); 71 } 72 73 // Slow path 74 uintptr_t good_addr = slow_path(addr); 75 76 // Self heal unless the address returned from the slow path is null, 77 // in which case resurrection was blocked and we must let the reference 78 // processor clear the oop. Mutators are not allowed to clear oops in 79 // these cases, since that would be similar to calling Reference.clear(), 80 // which would make the reference non-discoverable or silently dropped 81 // by the reference processor. 82 if (p != NULL && good_addr != 0) { 83 // The slow path returns a good/marked address, but we never mark oops 84 // in a weak load barrier so we always self heal with the remapped address. 85 const uintptr_t weak_good_addr = ZAddress::remapped(good_addr); 86 const uintptr_t prev_addr = Atomic::cmpxchg(weak_good_addr, (volatile uintptr_t*)p, addr); 87 if (prev_addr != addr) { 88 // Some other thread overwrote the oop. The new 89 // oop is guaranteed to be weak good or null. 90 assert(ZAddress::is_weak_good_or_null(prev_addr), "Bad weak overwrite"); 91 92 // Return the good address instead of the weak good address 93 // to ensure that the currently active heap view is used. 94 good_addr = ZAddress::good_or_null(prev_addr); 95 } 96 } 97 98 return ZOop::to_oop(good_addr); 99 } 100 101 template <ZBarrierFastPath fast_path, ZBarrierSlowPath slow_path> 102 inline void ZBarrier::root_barrier(oop* p, oop o) { 103 const uintptr_t addr = ZOop::to_address(o); 104 105 // Fast path 106 if (fast_path(addr)) { 107 return; 108 } 109 110 // Slow path 111 const uintptr_t good_addr = slow_path(addr); 112 113 // Non-atomic healing helps speed up root scanning. This is safe to do 114 // since we are always healing roots in a safepoint, which means we are 115 // never racing with mutators modifying roots while we are healing them. 116 // It's also safe in case multiple GC threads try to heal the same root, 117 // since they would always heal the root in the same way and it does not 118 // matter in which order it happens. 119 *p = ZOop::to_oop(good_addr); 120 } 121 122 inline bool ZBarrier::is_null_fast_path(uintptr_t addr) { 123 return ZAddress::is_null(addr); 124 } 125 126 inline bool ZBarrier::is_good_or_null_fast_path(uintptr_t addr) { 127 return ZAddress::is_good_or_null(addr); 128 } 129 130 inline bool ZBarrier::is_weak_good_or_null_fast_path(uintptr_t addr) { 131 return ZAddress::is_weak_good_or_null(addr); 132 } 133 134 inline bool ZBarrier::is_resurrection_blocked(volatile oop* p, oop* o) { 135 const bool is_blocked = ZResurrection::is_blocked(); 136 137 // Reload oop after checking the resurrection blocked state. This is 138 // done to prevent a race where we first load an oop, which is logically 139 // null but not yet cleared, then this oop is cleared by the reference 140 // processor and resurrection is unblocked. At this point the mutator 141 // would see the unblocked state and pass this invalid oop through the 142 // normal barrier path, which would incorrectly try to mark this oop. 143 if (p != NULL) { 144 // First assign to reloaded_o to avoid compiler warning about 145 // implicit dereference of volatile oop. 146 const oop reloaded_o = *p; 147 *o = reloaded_o; 148 } 149 150 return is_blocked; 151 } 152 153 // 154 // Load barrier 155 // 156 inline oop ZBarrier::load_barrier_on_oop(oop o) { 157 return load_barrier_on_oop_field_preloaded((oop*)NULL, o); 158 } 159 160 inline oop ZBarrier::load_barrier_on_oop_field(volatile oop* p) { 161 const oop o = *p; 162 return load_barrier_on_oop_field_preloaded(p, o); 163 } 164 165 inline oop ZBarrier::load_barrier_on_oop_field_preloaded(volatile oop* p, oop o) { 166 return barrier<is_good_or_null_fast_path, load_barrier_on_oop_slow_path>(p, o); 167 } 168 169 inline void ZBarrier::load_barrier_on_oop_array(volatile oop* p, size_t length) { 170 for (volatile const oop* const end = p + length; p < end; p++) { 171 load_barrier_on_oop_field(p); 172 } 173 } 174 175 inline oop ZBarrier::load_barrier_on_weak_oop_field_preloaded(volatile oop* p, oop o) { 176 if (is_resurrection_blocked(p, &o)) { 177 return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_weak_oop_slow_path>(p, o); 178 } 179 180 return load_barrier_on_oop_field_preloaded(p, o); 181 } 182 183 inline oop ZBarrier::load_barrier_on_phantom_oop_field_preloaded(volatile oop* p, oop o) { 184 if (is_resurrection_blocked(p, &o)) { 185 return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_phantom_oop_slow_path>(p, o); 186 } 187 188 return load_barrier_on_oop_field_preloaded(p, o); 189 } 190 191 // 192 // Weak load barrier 193 // 194 inline oop ZBarrier::weak_load_barrier_on_oop_field_preloaded(volatile oop* p, oop o) { 195 return weak_barrier<is_weak_good_or_null_fast_path, weak_load_barrier_on_oop_slow_path>(p, o); 196 } 197 198 inline oop ZBarrier::weak_load_barrier_on_weak_oop(oop o) { 199 return weak_load_barrier_on_weak_oop_field_preloaded((oop*)NULL, o); 200 } 201 202 inline oop ZBarrier::weak_load_barrier_on_weak_oop_field(volatile oop* p) { 203 const oop o = *p; 204 return weak_load_barrier_on_weak_oop_field_preloaded(p, o); 205 } 206 207 inline oop ZBarrier::weak_load_barrier_on_weak_oop_field_preloaded(volatile oop* p, oop o) { 208 if (is_resurrection_blocked(p, &o)) { 209 return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_weak_oop_slow_path>(p, o); 210 } 211 212 return weak_load_barrier_on_oop_field_preloaded(p, o); 213 } 214 215 inline oop ZBarrier::weak_load_barrier_on_phantom_oop(oop o) { 216 return weak_load_barrier_on_phantom_oop_field_preloaded((oop*)NULL, o); 217 } 218 219 inline oop ZBarrier::weak_load_barrier_on_phantom_oop_field(volatile oop* p) { 220 const oop o = *p; 221 return weak_load_barrier_on_phantom_oop_field_preloaded(p, o); 222 } 223 224 inline oop ZBarrier::weak_load_barrier_on_phantom_oop_field_preloaded(volatile oop* p, oop o) { 225 if (is_resurrection_blocked(p, &o)) { 226 return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_phantom_oop_slow_path>(p, o); 227 } 228 229 return weak_load_barrier_on_oop_field_preloaded(p, o); 230 } 231 232 // 233 // Is alive barrier 234 // 235 inline bool ZBarrier::is_alive_barrier_on_weak_oop(oop o) { 236 // Check if oop is logically non-null. This operation 237 // is only valid when resurrection is blocked. 238 assert(ZResurrection::is_blocked(), "Invalid phase"); 239 return weak_load_barrier_on_weak_oop(o) != NULL; 240 } 241 242 inline bool ZBarrier::is_alive_barrier_on_phantom_oop(oop o) { 243 // Check if oop is logically non-null. This operation 244 // is only valid when resurrection is blocked. 245 assert(ZResurrection::is_blocked(), "Invalid phase"); 246 return weak_load_barrier_on_phantom_oop(o) != NULL; 247 } 248 249 // 250 // Keep alive barrier 251 // 252 inline void ZBarrier::keep_alive_barrier_on_weak_oop_field(volatile oop* p) { 253 // This operation is only valid when resurrection is blocked. 254 assert(ZResurrection::is_blocked(), "Invalid phase"); 255 const oop o = *p; 256 barrier<is_good_or_null_fast_path, keep_alive_barrier_on_weak_oop_slow_path>(p, o); 257 } 258 259 inline void ZBarrier::keep_alive_barrier_on_phantom_oop_field(volatile oop* p) { 260 // This operation is only valid when resurrection is blocked. 261 assert(ZResurrection::is_blocked(), "Invalid phase"); 262 const oop o = *p; 263 barrier<is_good_or_null_fast_path, keep_alive_barrier_on_phantom_oop_slow_path>(p, o); 264 } 265 266 // 267 // Mark barrier 268 // 269 inline void ZBarrier::mark_barrier_on_oop_field(volatile oop* p, bool finalizable) { 270 // The fast path only checks for null since the GC worker 271 // threads doing marking wants to mark through good oops. 272 const oop o = *p; 273 274 if (finalizable) { 275 barrier<is_null_fast_path, mark_barrier_on_finalizable_oop_slow_path>(p, o); 276 } else { 277 barrier<is_null_fast_path, mark_barrier_on_oop_slow_path>(p, o); 278 } 279 } 280 281 inline void ZBarrier::mark_barrier_on_oop_array(volatile oop* p, size_t length, bool finalizable) { 282 for (volatile const oop* const end = p + length; p < end; p++) { 283 mark_barrier_on_oop_field(p, finalizable); 284 } 285 } 286 287 inline void ZBarrier::mark_barrier_on_root_oop_field(oop* p) { 288 const oop o = *p; 289 root_barrier<is_good_or_null_fast_path, mark_barrier_on_root_oop_slow_path>(p, o); 290 } 291 292 // 293 // Relocate barrier 294 // 295 inline void ZBarrier::relocate_barrier_on_root_oop_field(oop* p) { 296 const oop o = *p; 297 root_barrier<is_good_or_null_fast_path, relocate_barrier_on_root_oop_slow_path>(p, o); 298 } 299 300 #endif // SHARE_GC_Z_ZBARRIER_INLINE_HPP