threadCritical_windows.cpp revision 1472:c18cbe5936b8 
1/*
2 * Copyright (c) 2001, 2003, 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.
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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
36static bool initialized = false;
37static volatile jint lock_count = -1;
38static HANDLE lock_event;
39static 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
52void ThreadCritical::initialize() {
53}
54
55void 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
62ThreadCritical::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
91ThreadCritical::~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}
107