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comparison src/os/windows/vm/threadCritical_windows.cpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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children c18cbe5936b8
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-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 2001-2003 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 # include "incls/_precompiled.incl"
26 # include "incls/_threadCritical_windows.cpp.incl"
27
28 // OS-includes here
29 # include <windows.h>
30 # include <winbase.h>
31
32 //
33 // See threadCritical.hpp for details of this class.
34 //
35
36 static bool initialized = false;
37 static volatile jint lock_count = -1;
38 static HANDLE lock_event;
39 static DWORD lock_owner = -1;
40
41 //
42 // Note that Microsoft's critical region code contains a race
43 // condition, and is not suitable for use. A thread holding the
44 // critical section cannot safely suspend a thread attempting
45 // to enter the critical region. The failure mode is that both
46 // threads are permanently suspended.
47 //
48 // I experiemented with the use of ordinary windows mutex objects
49 // and found them ~30 times slower than the critical region code.
50 //
51
52 void ThreadCritical::initialize() {
53 }
54
55 void ThreadCritical::release() {
56 assert(lock_owner == -1, "Mutex being deleted while owned.");
57 assert(lock_count == -1, "Mutex being deleted while recursively locked");
58 assert(lock_event != NULL, "Sanity check");
59 CloseHandle(lock_event);
60 }
61
62 ThreadCritical::ThreadCritical() {
63 DWORD current_thread = GetCurrentThreadId();
64
65 if (lock_owner != current_thread) {
66 // Grab the lock before doing anything.
67 while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {
68 if (initialized) {
69 DWORD ret = WaitForSingleObject(lock_event, INFINITE);
70 assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");
71 }
72 }
73
74 // Make sure the event object is allocated.
75 if (!initialized) {
76 // Locking will not work correctly unless this is autoreset.
77 lock_event = CreateEvent(NULL, false, false, NULL);
78 initialized = true;
79 }
80
81 assert(lock_owner == -1, "Lock acquired illegally.");
82 lock_owner = current_thread;
83 } else {
84 // Atomicity isn't required. Bump the recursion count.
85 lock_count++;
86 }
87
88 assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");
89 }
90
91 ThreadCritical::~ThreadCritical() {
92 assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");
93 assert(lock_count >= 0, "Attempt to unlock when already unlocked");
94
95 if (lock_count == 0) {
96 // We're going to unlock
97 lock_owner = -1;
98 lock_count = -1;
99 // No lost wakeups, lock_event stays signaled until reset.
100 DWORD ret = SetEvent(lock_event);
101 assert(ret != 0, "unexpected return value from SetEvent");
102 } else {
103 // Just unwinding a recursive lock;
104 lock_count--;
105 }
106 }