1 /* 2 * Copyright (c) 1997, 2013, 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 "runtime/thread.hpp" 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 // Using a spin lock since we are part of the mutex impl. 63 // 8028280: using concurrent free list without memory management can leak 64 // pretty badly it turns out. 65 Thread::SpinAcquire(&ListLock, "ParkEventFreeListAllocate"); 66 { 67 ev = FreeList; 68 if (ev != NULL) { 69 FreeList = ev->FreeNext; 70 } 71 } 72 Thread::SpinRelease(&ListLock); 73 74 if (ev != NULL) { 75 guarantee (ev->AssociatedWith == NULL, "invariant") ; 76 } else { 77 // Do this the hard way -- materialize a new ParkEvent. 78 ev = new ParkEvent () ; 79 guarantee ((intptr_t(ev) & 0xFF) == 0, "invariant") ; 80 } 81 ev->reset() ; // courtesy to caller 82 ev->AssociatedWith = t ; // Associate ev with t 83 ev->FreeNext = NULL ; 84 return ev ; 85 } 86 87 void ParkEvent::Release (ParkEvent * ev) { 88 if (ev == NULL) return ; 89 guarantee (ev->FreeNext == NULL , "invariant") ; 90 ev->AssociatedWith = NULL ; 91 // Note that if we didn't have the TSM/immortal constraint, then 92 // when reattaching we could trim the list. 93 Thread::SpinAcquire(&ListLock, "ParkEventFreeListRelease"); 94 { 95 ev->FreeNext = FreeList; 96 FreeList = ev; 97 } 98 Thread::SpinRelease(&ListLock); 99 } 100 101 // Override operator new and delete so we can ensure that the 102 // least significant byte of ParkEvent addresses is 0. 103 // Beware that excessive address alignment is undesirable 104 // as it can result in D$ index usage imbalance as 105 // well as bank access imbalance on Niagara-like platforms, 106 // although Niagara's hash function should help. 107 108 void * ParkEvent::operator new (size_t sz) throw() { 109 return (void *) ((intptr_t (AllocateHeap(sz + 256, mtInternal, CALLER_PC)) + 256) & -256) ; 110 } 111 112 void ParkEvent::operator delete (void * a) { 113 // ParkEvents are type-stable and immortal ... 114 ShouldNotReachHere(); 115 } 116 117 118 // 6399321 As a temporary measure we copied & modified the ParkEvent:: 119 // allocate() and release() code for use by Parkers. The Parker:: forms 120 // will eventually be removed as we consolide and shift over to ParkEvents 121 // for both builtin synchronization and JSR166 operations. 122 123 volatile int Parker::ListLock = 0 ; 124 Parker * volatile Parker::FreeList = NULL ; 125 126 Parker * Parker::Allocate (JavaThread * t) { 127 guarantee (t != NULL, "invariant") ; 128 Parker * p ; 129 130 // Start by trying to recycle an existing but unassociated 131 // Parker from the global free list. 132 // 8028280: using concurrent free list without memory management can leak 133 // pretty badly it turns out. 134 Thread::SpinAcquire(&ListLock, "ParkerFreeListAllocate"); 135 { 136 p = FreeList; 137 if (p != NULL) { 138 FreeList = p->FreeNext; 139 } 140 } 141 Thread::SpinRelease(&ListLock); 142 143 if (p != NULL) { 144 guarantee (p->AssociatedWith == NULL, "invariant") ; 145 } else { 146 // Do this the hard way -- materialize a new Parker.. 147 p = new Parker() ; 148 } 149 p->AssociatedWith = t ; // Associate p with t 150 p->FreeNext = NULL ; 151 return p ; 152 } 153 154 155 void Parker::Release (Parker * p) { 156 if (p == NULL) return ; 157 guarantee (p->AssociatedWith != NULL, "invariant") ; 158 guarantee (p->FreeNext == NULL , "invariant") ; 159 p->AssociatedWith = NULL ; 160 161 Thread::SpinAcquire(&ListLock, "ParkerFreeListRelease"); 162 { 163 p->FreeNext = FreeList; 164 FreeList = p; 165 } 166 Thread::SpinRelease(&ListLock); 167 } 168