ACE/examples/APG/ThreadSafety/Mutex.cpp

   1 #include "ace/config-lite.h"
   2 #if defined (ACE_HAS_THREADS)
   3
   4 #include "ace/Synch.h"
   5 #include "ace/Guard_T.h"
   6
   7 class LogMessage
   8 {
   9 public:
  10   enum { CRITICAL, NORMAL};
  11
  12   virtual ~LogMessage ()
  13   {
  14   }
  15
  16   virtual int priority ()
  17   {
  18     return NORMAL;
  19   }
  20 };
  21
  22 class CriticalLogMessage : public LogMessage
  23 {
  24   virtual int priority ()
  25   {
  26     return LogMessage::CRITICAL;
  27   }
  28 };
  29
  30 // Listing 1 code/ch14
  31 typedef ACE_Thread_Mutex MUTEX;
  32 class Logger
  33 {
  34 public:
  35   void log (LogMessage *msg)
  36   {
  37     ACE_GUARD (MUTEX, mon, mutex_);
  38     if (msg->priority () == LogMessage::CRITICAL)
  39       logCritical (msg);
  40   }
  41
  42   void logCritical (LogMessage *)
  43   {
  44     // Acquires the same mutex as log()!
  45     ACE_GUARD(MUTEX, mon, mutex_);
  46   }
  47
  48 private:
  49   MUTEX mutex_;
  50 };
  51
  52 static Logger logger;
  53
  54 int ACE_TMAIN (int, ACE_TCHAR *[])
  55 {
  56   CriticalLogMessage cm;
  57   logger.log(&cm);  // Will cause deadlock.
  58   return 0;
  59 }
  60 // Listing 1
  61
  62 #else
  63 #include "ace/OS_main.h"
  64 #include "ace/OS_NS_stdio.h"
  65
  66 int ACE_TMAIN (int, ACE_TCHAR *[])
  67 {
  68   ACE_OS::puts (ACE_TEXT ("This example requires threads."));
  69   return 0;
  70 }
  71
  72 #endif /* ACE_HAS_THREADS */