threadCritical_windows.cpp revision 6646:b596a1063e90 
1/*
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25#include "precompiled.hpp"
26#include "runtime/atomic.inline.hpp"
27#include "runtime/thread.inline.hpp"
28#include "runtime/threadCritical.hpp"
29
30// OS-includes here
31# include <windows.h>
32# include <winbase.h>
33
34//
35// See threadCritical.hpp for details of this class.
36//
37
38static bool initialized = false;
39static volatile jint lock_count = -1;
40static HANDLE lock_event;
41static DWORD lock_owner = -1;
42
43//
44// Note that Microsoft's critical region code contains a race
45// condition, and is not suitable for use. A thread holding the
46// critical section cannot safely suspend a thread attempting
47// to enter the critical region. The failure mode is that both
48// threads are permanently suspended.
49//
50// I experiemented with the use of ordinary windows mutex objects
51// and found them ~30 times slower than the critical region code.
52//
53
54void ThreadCritical::initialize() {
55}
56
57void ThreadCritical::release() {
58  assert(lock_owner == -1, "Mutex being deleted while owned.");
59  assert(lock_count == -1, "Mutex being deleted while recursively locked");
60  assert(lock_event != NULL, "Sanity check");
61  CloseHandle(lock_event);
62}
63
64ThreadCritical::ThreadCritical() {
65  DWORD current_thread = GetCurrentThreadId();
66
67  if (lock_owner != current_thread) {
68    // Grab the lock before doing anything.
69    while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {
70      if (initialized) {
71        DWORD ret = WaitForSingleObject(lock_event,  INFINITE);
72        assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");
73      }
74    }
75
76    // Make sure the event object is allocated.
77    if (!initialized) {
78      // Locking will not work correctly unless this is autoreset.
79      lock_event = CreateEvent(NULL, false, false, NULL);
80      initialized = true;
81    }
82
83    assert(lock_owner == -1, "Lock acquired illegally.");
84    lock_owner = current_thread;
85  } else {
86    // Atomicity isn't required. Bump the recursion count.
87    lock_count++;
88  }
89
90  assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");
91}
92
93ThreadCritical::~ThreadCritical() {
94  assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");
95  assert(lock_count >= 0, "Attempt to unlock when already unlocked");
96
97  if (lock_count == 0) {
98    // We're going to unlock
99    lock_owner = -1;
100    lock_count = -1;
101    // No lost wakeups, lock_event stays signaled until reset.
102    DWORD ret = SetEvent(lock_event);
103    assert(ret != 0, "unexpected return value from SetEvent");
104  } else {
105    // Just unwinding a recursive lock;
106    lock_count--;
107  }
108}
109