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 p->_counter = 0;
152 return p ;
153 }
154
155
156 void Parker::Release (Parker * p) {
157 if (p == NULL) return ;
158 guarantee (p->AssociatedWith != NULL, "invariant") ;
159 guarantee (p->FreeNext == NULL , "invariant") ;
160
161 int status = pthread_mutex_lock(p->_mutex);
162 assert(status == 0, "invariant");
163 {
164 p->AssociatedWith = NULL;
165 }
166 pthread_mutex_unlock(p->_mutex);
167 assert(status == 0, "invariant");
168
169 Thread::SpinAcquire(&ListLock, "ParkerFreeListRelease");
170 {
171 p->FreeNext = FreeList;
172 FreeList = p;
173 }
174 Thread::SpinRelease(&ListLock);
175 }
176