ACE/ace/SV_Semaphore_Complex.cpp

   1 #include "ace/SV_Semaphore_Complex.h"
   2 #include "ace/Log_Category.h"
   3 #include "ace/OS_NS_Thread.h"
   4 #if defined (ACE_HAS_ALLOC_HOOKS)
   5 # include "ace/Malloc_Base.h"
   6 #endif /* ACE_HAS_ALLOC_HOOKS */
   7
   8 #if !defined (__ACE_INLINE__)
   9 #include "ace/SV_Semaphore_Complex.inl"
  10 #endif /* __ACE_INLINE__ */
  11
  12 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  13
  14 ACE_ALLOC_HOOK_DEFINE(ACE_SV_Semaphore_Complex)
  15
  16 void
  17 ACE_SV_Semaphore_Complex::dump () const
  18 {
  19 #if defined (ACE_HAS_DUMP)
  20   ACE_TRACE ("ACE_SV_Semaphore_Complex::dump");
  21 #endif /* ACE_HAS_DUMP */
  22 }
  23
  24 // initial value of process
  25 const int ACE_SV_Semaphore_Complex::BIGCOUNT_ = 10000;
  26
  27 // Define the ACE_SV_Semaphore operation arrays for the semop() calls.
  28 sembuf ACE_SV_Semaphore_Complex::op_lock_[2] =
  29 {
  30   {0, 0, 0},                    // Wait for [0] (lock) to equal 0
  31   {0, 1, SEM_UNDO},             // then increment [0] to 1 - this locks it.
  32                                 // UNDO to release the lock if processes exit
  33                                 // before explicitly unlocking.
  34 };
  35
  36 sembuf ACE_SV_Semaphore_Complex::op_endcreate_[2] =
  37 {
  38   {1, -1, SEM_UNDO},            // Decrement [1] (proc counter) with undo on
  39                                 // exit, UNDO to adjust proc counter if
  40                                 // process exits before explicitly calling close()
  41   {0, -1, SEM_UNDO},            // the decrement [0] (lock) back to 0
  42 };
  43
  44 sembuf ACE_SV_Semaphore_Complex::op_open_[1] =
  45 {
  46   {1, -1, SEM_UNDO},            // Decrement [1] (proc counter) with undo on
  47                                 // exit.
  48 };
  49
  50 sembuf ACE_SV_Semaphore_Complex::op_close_[3] =
  51 {
  52   {0, 0, 0},                    // Wait for [0] (lock) to equal 0
  53   {0, 1, SEM_UNDO},             // then increment [0] to 1 - this lock it
  54   {1, 1, SEM_UNDO},             // then increment [1] (proc counter)
  55 };
  56
  57 sembuf ACE_SV_Semaphore_Complex::op_unlock_[1] =
  58 {
  59   {0, -1, SEM_UNDO},            // Decrement [0] (lock) back to 0
  60 };
  61
  62 // Open or create an array of SV_Semaphores.  We return 0 if all is OK, else -1.
  63
  64 int
  65 ACE_SV_Semaphore_Complex::open (key_t k,
  66                                 short create,
  67                                 int initial_value,
  68                                 u_short nsems,
  69                                 mode_t perms)
  70 {
  71   ACE_TRACE ("ACE_SV_Semaphore_Complex::open");
  72 #ifdef ACE_HAS_SYSV_IPC
  73   if (k == IPC_PRIVATE)
  74     return -1;
  75 #endif
  76
  77   this->key_ = k;
  78
  79   // Must include a count for the 2 additional semaphores we use
  80   // internally.
  81   this->sem_number_ = nsems + 2;
  82
  83   if (create == ACE_SV_Semaphore_Complex::ACE_CREATE)
  84     {
  85       int result;
  86
  87       do
  88         {
  89           this->internal_id_ = ACE_OS::semget
  90             (this->key_,
  91              (u_short) 2 + nsems,
  92              perms | ACE_SV_Semaphore_Complex::ACE_CREATE);
  93
  94           if (this->internal_id_ == -1)
  95             return -1; // permission problem or tables full
  96
  97           // When the <ACE_SV_Semaphore_Complex> is created, we know
  98           // that the value of all 3 members is 0.  Get a lock on the
  99           // <ACE_SV_Semaphore_Complex> by waiting for [0] to equal 0,
 100           // then increment it.
 101
 102           // There is a race condition here. There is the possibility
 103           // that between the <semget> above and the <semop> below,
 104           // another process can call out <close> function which can
 105           // remove the <ACE_SV_Semaphore> if that process is the last
 106           // one using it.  Therefor we handle the error condition of
 107           // an invalid <ACE_SV_Semaphore> ID specifically below, and
 108           // if it does happen, we just go back and create it again.
 109           result = ACE_OS::semop (this->internal_id_,
 110                                   &ACE_SV_Semaphore_Complex::op_lock_[0],
 111                                   2);
 112         }
 113       while (result == -1 && (errno == EINVAL || errno == EIDRM));
 114
 115       if (result == -1)
 116         return -1;
 117
 118       // Get the value of the process counter. If it equals 0, then no
 119       // one has initialized the ACE_SV_Semaphore yet.
 120
 121       int semval = ACE_SV_Semaphore_Simple::control (GETVAL, 0, 1);
 122
 123       if (semval == -1)
 124 #ifdef ACE_HAS_SYSV_IPC
 125         return this->init ();
 126 #else
 127         return -1;
 128 #endif
 129       else if (semval == 0)
 130         {
 131           // We should initialize by doing a SETALL, but that would
 132           // clear the adjust value that we set when we locked the
 133           // ACE_SV_Semaphore above. Instead we do system calls to
 134           // initialize [1], as well as all the nsems SV_Semaphores.
 135
 136           if (ACE_SV_Semaphore_Simple::control (SETVAL,
 137                                                 ACE_SV_Semaphore_Complex::BIGCOUNT_,
 138                                                 1) == -1)
 139             return -1;
 140           else
 141             for (u_short i = 0; i < nsems; i++)
 142               if (this->control (SETVAL, initial_value, i) == -1)
 143                 return -1;
 144         }
 145
 146       // Decrement the process counter and then release the lock.
 147       return ACE_OS::semop (this->internal_id_,
 148                             &ACE_SV_Semaphore_Complex::op_endcreate_[0],
 149                             2);
 150     }
 151   else
 152     {
 153       this->internal_id_ = ACE_OS::semget (this->key_, 2 + nsems, 0);
 154       if (this->internal_id_ == -1)
 155         return -1;                      // doesn't exist or tables full
 156
 157       // Decrement the process counter. We don't need a lock to do this.
 158       if (ACE_OS::semop (this->internal_id_,
 159                          &ACE_SV_Semaphore_Complex::op_open_[0], 1) < 0)
 160 #ifdef ACE_HAS_SYSV_IPC
 161         return this->init ();
 162 #else
 163         return -1;
 164 #endif
 165       return 0;
 166     }
 167 }
 168
 169 int
 170 ACE_SV_Semaphore_Complex::open (const char *name,
 171                                 short flags,
 172                                 int initial_value,
 173                                 u_short nsems,
 174                                 mode_t perms)
 175 {
 176   ACE_TRACE ("ACE_SV_Semaphore_Complex::open");
 177   return this->open (ACE_SV_Semaphore_Simple::name_2_key (name),
 178                      flags, initial_value, nsems, perms);
 179 }
 180
 181 // Close a ACE_SV_Semaphore.  Unlike the remove above, this function
 182 // is for a process to call before it exits, when it is done with the
 183 // ACE_SV_Semaphore.  We "decrement" the counter of processes using
 184 // the ACE_SV_Semaphore, and if this was the last one, we can remove
 185 // the ACE_SV_Semaphore.
 186
 187 int
 188 ACE_SV_Semaphore_Complex::close ()
 189 {
 190   ACE_TRACE ("ACE_SV_Semaphore_Complex::close");
 191   int semval;
 192
 193 #ifdef ACE_HAS_SYSV_IPC
 194   if (this->key_ == (key_t) - 1 || this->internal_id_ == -1)
 195     return -1;
 196 #endif
 197
 198   // The following semop() first gets a lock on the ACE_SV_Semaphore,
 199   // then increments [1] - the process number.
 200
 201   if (ACE_OS::semop (this->internal_id_,
 202                      &ACE_SV_Semaphore_Complex::op_close_[0],
 203                      3) == -1)
 204     return -1;
 205
 206   // Now that we have a lock, read the value of the process counter to
 207   // see if this is the last reference to the ACE_SV_Semaphore. There
 208   // is a race condition here - see the comments in create ().
 209
 210   if ((semval = ACE_SV_Semaphore_Simple::control (GETVAL, 0, 1)) == -1)
 211     return -1;
 212
 213   if (semval > ACE_SV_Semaphore_Complex::BIGCOUNT_)
 214     return -1;
 215   else if (semval == ACE_SV_Semaphore_Complex::BIGCOUNT_)
 216     return this->remove ();
 217   else
 218     {
 219       int result = ACE_OS::semop (this->internal_id_,
 220                                   &ACE_SV_Semaphore_Complex::op_unlock_[0], 1);
 221 #ifdef ACE_HAS_SYSV_IPC
 222       this->init ();
 223 #endif
 224       return result;
 225     }
 226 }
 227
 228 ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex (key_t k,
 229                                                     short flags,
 230                                                     int initial_value,
 231                                                     u_short nsems,
 232                                                     mode_t perms)
 233 {
 234   ACE_TRACE ("ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex");
 235   if (this->open (k, flags, initial_value, nsems, perms) == -1)
 236     ACELIB_ERROR ((LM_ERROR,  ACE_TEXT ("%p\n"),  ACE_TEXT ("ACE_SV_Semaphore_Complex")));
 237 }
 238
 239 ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex (const char *name,
 240                                                     short flags,
 241                                                     int initial_value,
 242                                                     u_short nsems,
 243                                                     mode_t perms)
 244 {
 245   ACE_TRACE ("ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex");
 246
 247   key_t key = ACE_DEFAULT_SEM_KEY;
 248
 249 #ifdef ACE_HAS_SYSV_IPC
 250   if (name != 0)
 251     key = this->name_2_key (name);
 252 #else
 253   ACE_UNUSED_ARG (name);
 254 #endif
 255
 256   if (this->open (key, flags, initial_value, nsems, perms) == -1)
 257     ACELIB_ERROR ((LM_ERROR,  ACE_TEXT ("%p\n"),  ACE_TEXT ("ACE_SV_Semaphore_Complex")));
 258 }
 259
 260 ACE_SV_Semaphore_Complex::~ACE_SV_Semaphore_Complex ()
 261 {
 262   ACE_TRACE ("ACE_SV_Semaphore_Complex::~ACE_SV_Semaphore_Complex");
 263   if (this->internal_id_ >= 0)
 264     this->close ();
 265 }
 266
 267 ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex ()
 268 {
 269   ACE_TRACE ("ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex");
 270 #ifdef ACE_HAS_SYSV_IPC
 271   this->init ();
 272 #endif
 273 }
 274
 275 ACE_END_VERSIONED_NAMESPACE_DECL