1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  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
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  24 
  25 // ThreadCritical is used to protect short non-blocking critical sections.
  26 // This class must use no vm facilities that require initialization.
  27 // It is used very early in the vm's initialization, in allocation
  28 // code and other areas. ThreadCritical regions are reentrant.
  29 //
  30 // Due to race conditions during vm exit, some of the os level
  31 // synchronization primitives may not be deallocated at exit. It
  32 // is a good plan to implement the platform dependent sections of
  33 // code with resources that are recoverable during process
  34 // cleanup by the os. Calling the initialize method before use
  35 // is also problematic, it is best to use preinitialized primitives
  36 // if possible. As an example:
  37 //
  38 // mutex_t  mp  =  DEFAULTMUTEX;
  39 //
  40 // Also note that this class is declared as a StackObj to enforce
  41 // block structured short locks. It cannot be declared a ResourceObj
  42 // or CHeapObj, due to initialization issues.
  43 
  44 class ThreadCritical : public StackObj {
  45  friend class os;
  46  private:
  47   static void initialize();
  48   static void release();
  49 
  50  public:
  51   ThreadCritical();
  52   ~ThreadCritical();
  53 };