ACE/ace/Mutex.h

   1 // -*- C++ -*-
   2
   3 //==========================================================================
   4 /**
   5  *  @file    Mutex.h
   6  *
   7  *  @author Douglas C. Schmidt <d.schmidt@vanderbilt.edu>
   8  */
   9 //==========================================================================
  10
  11 #ifndef ACE_MUTEX_H
  12 #define ACE_MUTEX_H
  13
  14 #include /**/ "ace/pre.h"
  15
  16 #include /**/ "ace/ACE_export.h"
  17
  18 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  19 # pragma once
  20 #endif /* ACE_LACKS_PRAGMA_ONCE */
  21
  22 #include "ace/OS_NS_Thread.h"
  23 #include "ace/OS_NS_unistd.h"
  24 #include "ace/os_include/os_fcntl.h"
  25
  26 #if !defined (ACE_DEFAULT_MUTEX_A)
  27 # define ACE_DEFAULT_MUTEX_A "ACE_MUTEX"
  28 #endif /* ACE_DEFAULT_MUTEX_A */
  29
  30 #if defined (ACE_HAS_WCHAR)
  31 # define ACE_DEFAULT_MUTEX_W ACE_TEXT_WIDE (ACE_DEFAULT_MUTEX_A)
  32 #endif /* ACE_HAS_WCHAR */
  33
  34 #define ACE_DEFAULT_MUTEX ACE_TEXT (ACE_DEFAULT_MUTEX_A)
  35
  36 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  37
  38 class ACE_Time_Value;
  39
  40 /**
  41  * @class ACE_Mutex
  42  *
  43  * @brief @c ACE_Mutex wrapper (valid in same process or across
  44  *        processes (depending on @a TYPE flag)).  In general,
  45  *        however, we recommend using @a ACE_Process_Mutex or @a
  46  *        ACE_Thread_Mutex rather than @a ACE_Mutex.
  47  */
  48 class ACE_Export ACE_Mutex
  49 {
  50 public:
  51   /// Initialize the mutex.
  52   ACE_Mutex (int type = USYNC_THREAD,
  53              const ACE_TCHAR *name = 0,
  54              ACE_mutexattr_t *arg = 0,
  55              mode_t mode = ACE_DEFAULT_FILE_PERMS);
  56
  57   /// Implicitly destroy the mutex.
  58   ~ACE_Mutex ();
  59
  60   /// Explicitly destroy the mutex.
  61   /**
  62    * @note Only one thread should call this method since it doesn't
  63    *        protect against race conditions.
  64    */
  65   int remove ();
  66
  67   /// Acquire lock ownership (wait on queue if necessary).
  68   int acquire ();
  69
  70   /// Block the thread until the mutex is acquired or @a tv times out,
  71   /// in which case -1 is returned and @c errno == @c ETIME.
  72   /**
  73    * @note @a tv is assumed  to be in "absolute" rather than
  74    * "     relative" time.  The value of @a tv is updated upon return
  75    *       to show the actual(absolute) acquisition time.
  76    */
  77   int acquire (ACE_Time_Value &tv);
  78
  79   /// Block the thread until the mutex is acquired or @a *tv times
  80   /// out, in which case -1 is returned and @c errno == @c ETIME.
  81   /**
  82    * If @a tv == 0 then call @c acquire() directly.  Otherwise, block
  83    * the thread until the mutex is acquired or @a tv times out, in
  84    * which case -1 is returned and @c errno == @c ETIME.
  85    *
  86    * @note @a *tv is assumed to be in "absolute" rather than
  87    *       "relative" time.  The value of @a *tv is updated upon
  88    *       return to show the actual (absolute) acquisition time.
  89    */
  90   int acquire (ACE_Time_Value *tv);
  91
  92   /// Conditionally acquire lock (i.e., don't wait on queue).
  93   /**
  94    * @return -1 on failure.  If we "failed" because someone
  95    *         else already had the lock, @c errno is set to @c EBUSY.
  96    */
  97   int tryacquire ();
  98
  99   /// Release lock and unblock a thread at head of queue.
 100   int release ();
 101
 102   /// Acquire mutex ownership.
 103   /**
 104    * This calls @c acquire and is only here to make the @c ACE_Mutex
 105    * interface consistent with the other synchronization APIs.
 106    */
 107   int acquire_read ();
 108
 109   /// Acquire mutex ownership.
 110   /**
 111    * This calls @c acquire and is only here to make the @c ACE_Mutex
 112    * interface consistent with the other synchronization APIs.
 113    */
 114   int acquire_write ();
 115
 116   /// Conditionally acquire mutex (i.e., won't block).
 117   /**
 118    * This calls @c tryacquire and is only here to make the @c ACE_Mutex
 119    * interface consistent with the other synchronization APIs.
 120    *
 121    * @return -1 on failure.  If we "failed" because someone else
 122    *         already had the lock, @c errno is set to @c EBUSY.
 123    */
 124   int tryacquire_read ();
 125
 126   /// Conditionally acquire mutex (i.e., won't block).
 127   /**
 128    * This calls @c tryacquire and is only here to make the @c ACE_Mutex
 129    * interface consistent with the other synchronization APIs.
 130    *
 131    * @return -1 on failure.  If we "failed" because someone else
 132    *         already had the lock, @c errno is set to @c EBUSY.
 133    */
 134   int tryacquire_write ();
 135
 136   /**
 137    * This is only here for consistency with the other synchronization
 138    * APIs and usability with Lock adapters. Assumes the caller already has
 139    * acquired the mutex and returns 0 in all cases.
 140    */
 141   int tryacquire_write_upgrade ();
 142
 143   /// Return the underlying mutex.
 144   const ACE_mutex_t &lock () const;
 145   ACE_mutex_t &lock ();
 146
 147   /// If a file was created as the underlying storage for the mutex,
 148   /// remove it from the filesystem (for process-shared mutexes).
 149   static int unlink (const ACE_TCHAR *name);
 150
 151   /// Dump the state of an object.
 152   void dump () const;
 153
 154   /// Declare the dynamic allocation hooks.
 155   ACE_ALLOC_HOOK_DECLARE;
 156
 157   // = This should be protected but some C++ compilers complain...
 158 public:
 159 #if defined ACE_HAS_PTHREADS && defined ACE_LACKS_MUTEXATTR_PSHARED
 160 # define ACE_MUTEX_USE_PROCESS_LOCK
 161 # define ACE_MUTEX_PROCESS_LOCK_IS_SEMA
 162   ACE_sema_t process_sema_;
 163   typedef ACE_sema_t Process_Lock;
 164 #elif defined ACE_HAS_PTHREADS
 165 # define ACE_MUTEX_USE_PROCESS_LOCK
 166 # define ACE_MUTEX_PROCESS_LOCK_IS_MUTEX
 167   typedef ACE_mutex_t Process_Lock;
 168 #endif
 169
 170 #ifdef ACE_MUTEX_USE_PROCESS_LOCK
 171   /// This lock resides in shared memory.
 172   Process_Lock *process_lock_;
 173
 174   /**
 175    * Remember the name of the mutex if we created it so we can unlink
 176    * it when we go away (only the actor that initialized the memory
 177    * can destroy it).
 178    */
 179   const ACE_TCHAR *lockname_;
 180 #endif /* ACE_MUTEX_USE_PROCESS_LOCK */
 181
 182   /// Mutex type supported by the OS.
 183   ACE_mutex_t lock_;
 184
 185   /// Keeps track of whether @c remove has been called yet to avoid
 186   /// multiple @c remove calls, e.g., explicitly and implicitly in the
 187   /// destructor.  This flag isn't protected by a lock, so make sure
 188   /// that you don't have multiple threads simultaneously calling
 189   /// @c remove on the same object, which is a bad idea anyway.
 190   bool removed_;
 191
 192 private:
 193   ACE_Mutex &operator= (const ACE_Mutex &) = delete;
 194   ACE_Mutex (const ACE_Mutex &) = delete;
 195 };
 196
 197 ACE_END_VERSIONED_NAMESPACE_DECL
 198
 199 #if defined (__ACE_INLINE__)
 200 #include "ace/Mutex.inl"
 201 #endif /* __ACE_INLINE__ */
 202
 203 #include /**/ "ace/post.h"
 204
 205 #endif /* ACE_MUTEX_H */