Mercurial > hg > graal-compiler
annotate src/share/vm/runtime/park.cpp @ 8504:86b4965f0c9a
-Cleanup code
author | Christos Kotselidis <christos.kotselidis@oracle.com> |
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date | Wed, 20 Mar 2013 21:39:24 +0100 |
parents | b9a9ed0f8eeb |
children | 9758d9f36299 |
rev | line source |
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1878 | 1 /* |
6842
b9a9ed0f8eeb
7197424: update copyright year to match last edit in jdk8 hotspot repository
mikael
parents:
6197
diff
changeset
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2 * Copyright (c) 1997, 2012, 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 | |
143 void * ParkEvent::operator new (size_t sz) { | |
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 | |
155 // will eventually be removed as we consolide and shift over to ParkEvents | |
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 |