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1 /*
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2 * Copyright 2001-2002 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // ThreadCritical is used to protect short non-blocking critical sections.
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26 // This class must use no vm facilities that require initialization.
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27 // It is used very early in the vm's initialization, in allocation
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28 // code and other areas. ThreadCritical regions are reentrant.
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29 //
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30 // Due to race conditions during vm exit, some of the os level
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31 // synchronization primitives may not be deallocated at exit. It
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32 // is a good plan to implement the platform dependant sections of
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33 // code with resources that are recoverable during process
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34 // cleanup by the os. Calling the initialize method before use
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35 // is also problematic, it is best to use preinitialized primitives
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36 // if possible. As an example:
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37 //
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38 // mutex_t mp = DEFAULTMUTEX;
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39 //
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40 // Also note that this class is declared as a StackObj to enforce
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41 // block structured short locks. It cannot be declared a ResourceObj
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42 // or CHeapObj, due to initialization issues.
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43
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44 class ThreadCritical : public StackObj {
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45 friend class os;
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46 private:
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47 static void initialize();
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48 static void release();
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49
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50 public:
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51 ThreadCritical();
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52 ~ThreadCritical();
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53 };
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