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.
  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 }