Mercurial > hg > graal-compiler
annotate src/share/vm/runtime/park.cpp @ 14309:63a4eb8bcd23
8025856: Fix typos in the GC code
Summary: Fix about 440 typos in comments in the VM code
Reviewed-by: mgerdin, tschatzl, coleenp, kmo, jcoomes
| author | jwilhelm |
|---|---|
| date | Thu, 23 Jan 2014 14:47:23 +0100 |
| parents | 9758d9f36299 |
| children | 2c95095271e9 |
| rev | line source |
|---|---|
| 1878 | 1 /* |
|
12146
9758d9f36299
8021954: VM SIGSEGV during classloading on MacOS; hs_err_pid file produced
coleenp
parents:
6842
diff
changeset
|
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. |
| 1878 | 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 | |
| 1972 | 25 #include "precompiled.hpp" |
| 26 #include "runtime/thread.hpp" | |
| 1878 | 27 |
| 28 | |
| 29 | |
| 30 // Lifecycle management for TSM ParkEvents. | |
| 31 // ParkEvents are type-stable (TSM). | |
| 32 // In our particular implementation they happen to be immortal. | |
| 33 // | |
| 34 // We manage concurrency on the FreeList with a CAS-based | |
| 35 // detach-modify-reattach idiom that avoids the ABA problems | |
| 36 // that would otherwise be present in a simple CAS-based | |
| 37 // push-pop implementation. (push-one and pop-all) | |
| 38 // | |
| 39 // Caveat: Allocate() and Release() may be called from threads | |
| 40 // other than the thread associated with the Event! | |
| 41 // If we need to call Allocate() when running as the thread in | |
| 42 // question then look for the PD calls to initialize native TLS. | |
| 43 // Native TLS (Win32/Linux/Solaris) can only be initialized or | |
| 44 // accessed by the associated thread. | |
| 45 // See also pd_initialize(). | |
| 46 // | |
| 47 // Note that we could defer associating a ParkEvent with a thread | |
| 48 // until the 1st time the thread calls park(). unpark() calls to | |
| 49 // an unprovisioned thread would be ignored. The first park() call | |
| 50 // for a thread would allocate and associate a ParkEvent and return | |
| 51 // immediately. | |
| 52 | |
| 53 volatile int ParkEvent::ListLock = 0 ; | |
| 54 ParkEvent * volatile ParkEvent::FreeList = NULL ; | |
| 55 | |
| 56 ParkEvent * ParkEvent::Allocate (Thread * t) { | |
| 57 // In rare cases -- JVM_RawMonitor* operations -- we can find t == null. | |
| 58 ParkEvent * ev ; | |
| 59 | |
| 60 // Start by trying to recycle an existing but unassociated | |
| 61 // ParkEvent from the global free list. | |
| 62 for (;;) { | |
| 63 ev = FreeList ; | |
| 64 if (ev == NULL) break ; | |
| 65 // 1: Detach - sequester or privatize the list | |
| 66 // Tantamount to ev = Swap (&FreeList, NULL) | |
| 67 if (Atomic::cmpxchg_ptr (NULL, &FreeList, ev) != ev) { | |
| 68 continue ; | |
| 69 } | |
| 70 | |
| 71 // We've detached the list. The list in-hand is now | |
| 72 // local to this thread. This thread can operate on the | |
| 73 // list without risk of interference from other threads. | |
| 74 // 2: Extract -- pop the 1st element from the list. | |
| 75 ParkEvent * List = ev->FreeNext ; | |
| 76 if (List == NULL) break ; | |
| 77 for (;;) { | |
| 78 // 3: Try to reattach the residual list | |
| 79 guarantee (List != NULL, "invariant") ; | |
| 80 ParkEvent * Arv = (ParkEvent *) Atomic::cmpxchg_ptr (List, &FreeList, NULL) ; | |
| 81 if (Arv == NULL) break ; | |
| 82 | |
| 83 // New nodes arrived. Try to detach the recent arrivals. | |
| 84 if (Atomic::cmpxchg_ptr (NULL, &FreeList, Arv) != Arv) { | |
| 85 continue ; | |
| 86 } | |
| 87 guarantee (Arv != NULL, "invariant") ; | |
| 88 // 4: Merge Arv into List | |
| 89 ParkEvent * Tail = List ; | |
| 90 while (Tail->FreeNext != NULL) Tail = Tail->FreeNext ; | |
| 91 Tail->FreeNext = Arv ; | |
| 92 } | |
| 93 break ; | |
| 94 } | |
| 95 | |
| 96 if (ev != NULL) { | |
| 97 guarantee (ev->AssociatedWith == NULL, "invariant") ; | |
| 98 } else { | |
| 99 // Do this the hard way -- materialize a new ParkEvent. | |
| 100 // In rare cases an allocating thread might detach a long list -- | |
| 101 // installing null into FreeList -- and then stall or be obstructed. | |
| 102 // A 2nd thread calling Allocate() would see FreeList == null. | |
| 103 // The list held privately by the 1st thread is unavailable to the 2nd thread. | |
| 104 // In that case the 2nd thread would have to materialize a new ParkEvent, | |
| 105 // even though free ParkEvents existed in the system. In this case we end up | |
| 106 // with more ParkEvents in circulation than we need, but the race is | |
| 107 // rare and the outcome is benign. Ideally, the # of extant ParkEvents | |
| 108 // is equal to the maximum # of threads that existed at any one time. | |
| 109 // Because of the race mentioned above, segments of the freelist | |
| 110 // can be transiently inaccessible. At worst we may end up with the | |
| 111 // # of ParkEvents in circulation slightly above the ideal. | |
| 112 // Note that if we didn't have the TSM/immortal constraint, then | |
| 113 // when reattaching, above, we could trim the list. | |
| 114 ev = new ParkEvent () ; | |
| 115 guarantee ((intptr_t(ev) & 0xFF) == 0, "invariant") ; | |
| 116 } | |
| 117 ev->reset() ; // courtesy to caller | |
| 118 ev->AssociatedWith = t ; // Associate ev with t | |
| 119 ev->FreeNext = NULL ; | |
| 120 return ev ; | |
| 121 } | |
| 122 | |
| 123 void ParkEvent::Release (ParkEvent * ev) { | |
| 124 if (ev == NULL) return ; | |
| 125 guarantee (ev->FreeNext == NULL , "invariant") ; | |
| 126 ev->AssociatedWith = NULL ; | |
| 127 for (;;) { | |
| 128 // Push ev onto FreeList | |
| 129 // The mechanism is "half" lock-free. | |
| 130 ParkEvent * List = FreeList ; | |
| 131 ev->FreeNext = List ; | |
| 132 if (Atomic::cmpxchg_ptr (ev, &FreeList, List) == List) break ; | |
| 133 } | |
| 134 } | |
| 135 | |
| 136 // Override operator new and delete so we can ensure that the | |
| 137 // least significant byte of ParkEvent addresses is 0. | |
| 138 // Beware that excessive address alignment is undesirable | |
| 139 // as it can result in D$ index usage imbalance as | |
| 140 // well as bank access imbalance on Niagara-like platforms, | |
| 141 // although Niagara's hash function should help. | |
| 142 | |
|
12146
9758d9f36299
8021954: VM SIGSEGV during classloading on MacOS; hs_err_pid file produced
coleenp
parents:
6842
diff
changeset
|
143 void * ParkEvent::operator new (size_t sz) throw() { |
| 6197 | 144 return (void *) ((intptr_t (AllocateHeap(sz + 256, mtInternal, CALLER_PC)) + 256) & -256) ; |
| 1878 | 145 } |
| 146 | |
| 147 void ParkEvent::operator delete (void * a) { | |
| 148 // ParkEvents are type-stable and immortal ... | |
| 149 ShouldNotReachHere(); | |
| 150 } | |
| 151 | |
| 152 | |
| 153 // 6399321 As a temporary measure we copied & modified the ParkEvent:: | |
| 154 // allocate() and release() code for use by Parkers. The Parker:: forms | |
| 14309 | 155 // will eventually be removed as we consolidate and shift over to ParkEvents |
| 1878 | 156 // for both builtin synchronization and JSR166 operations. |
| 157 | |
| 158 volatile int Parker::ListLock = 0 ; | |
| 159 Parker * volatile Parker::FreeList = NULL ; | |
| 160 | |
| 161 Parker * Parker::Allocate (JavaThread * t) { | |
| 162 guarantee (t != NULL, "invariant") ; | |
| 163 Parker * p ; | |
| 164 | |
| 165 // Start by trying to recycle an existing but unassociated | |
| 166 // Parker from the global free list. | |
| 167 for (;;) { | |
| 168 p = FreeList ; | |
| 169 if (p == NULL) break ; | |
| 170 // 1: Detach | |
| 171 // Tantamount to p = Swap (&FreeList, NULL) | |
| 172 if (Atomic::cmpxchg_ptr (NULL, &FreeList, p) != p) { | |
| 173 continue ; | |
| 174 } | |
| 175 | |
| 176 // We've detached the list. The list in-hand is now | |
| 177 // local to this thread. This thread can operate on the | |
| 178 // list without risk of interference from other threads. | |
| 179 // 2: Extract -- pop the 1st element from the list. | |
| 180 Parker * List = p->FreeNext ; | |
| 181 if (List == NULL) break ; | |
| 182 for (;;) { | |
| 183 // 3: Try to reattach the residual list | |
| 184 guarantee (List != NULL, "invariant") ; | |
| 185 Parker * Arv = (Parker *) Atomic::cmpxchg_ptr (List, &FreeList, NULL) ; | |
| 186 if (Arv == NULL) break ; | |
| 187 | |
| 188 // New nodes arrived. Try to detach the recent arrivals. | |
| 189 if (Atomic::cmpxchg_ptr (NULL, &FreeList, Arv) != Arv) { | |
| 190 continue ; | |
| 191 } | |
| 192 guarantee (Arv != NULL, "invariant") ; | |
| 193 // 4: Merge Arv into List | |
| 194 Parker * Tail = List ; | |
| 195 while (Tail->FreeNext != NULL) Tail = Tail->FreeNext ; | |
| 196 Tail->FreeNext = Arv ; | |
| 197 } | |
| 198 break ; | |
| 199 } | |
| 200 | |
| 201 if (p != NULL) { | |
| 202 guarantee (p->AssociatedWith == NULL, "invariant") ; | |
| 203 } else { | |
| 204 // Do this the hard way -- materialize a new Parker.. | |
| 205 // In rare cases an allocating thread might detach | |
| 206 // a long list -- installing null into FreeList --and | |
| 207 // then stall. Another thread calling Allocate() would see | |
| 208 // FreeList == null and then invoke the ctor. In this case we | |
| 209 // end up with more Parkers in circulation than we need, but | |
| 210 // the race is rare and the outcome is benign. | |
| 211 // Ideally, the # of extant Parkers is equal to the | |
| 212 // maximum # of threads that existed at any one time. | |
| 213 // Because of the race mentioned above, segments of the | |
| 214 // freelist can be transiently inaccessible. At worst | |
| 215 // we may end up with the # of Parkers in circulation | |
| 216 // slightly above the ideal. | |
| 217 p = new Parker() ; | |
| 218 } | |
| 219 p->AssociatedWith = t ; // Associate p with t | |
| 220 p->FreeNext = NULL ; | |
| 221 return p ; | |
| 222 } | |
| 223 | |
| 224 | |
| 225 void Parker::Release (Parker * p) { | |
| 226 if (p == NULL) return ; | |
| 227 guarantee (p->AssociatedWith != NULL, "invariant") ; | |
| 228 guarantee (p->FreeNext == NULL , "invariant") ; | |
| 229 p->AssociatedWith = NULL ; | |
| 230 for (;;) { | |
| 231 // Push p onto FreeList | |
| 232 Parker * List = FreeList ; | |
| 233 p->FreeNext = List ; | |
| 234 if (Atomic::cmpxchg_ptr (p, &FreeList, List) == List) break ; | |
| 235 } | |
| 236 } | |
| 237 |