Obtain a write lock on a resource. This will spin until either the lock is granted or the lock is deactivated (host entity destructed). And then spin until the read count falls to zero. This latter step ensures no thread can read the resource during a write.

Declared in file: hzLock.h
Defined in file : hzLock.cpp

Function Logic:

Function body:

hzEcode hzLockRW::LockWrite (int32_t nTries)
{
   //  Obtain a write lock on a resource. This will spin until either the lock is granted or the lock is deactivated (host entity destructed). And
   //  then spin until the read count falls to zero. This latter step ensures no thread can read the resource during a write.
   //  
   //  Arguments: 1) nTries Number of retries (in thousands) before abandoning efforts to obtain the lock
   //  
   //  Returns: E_NOTFOUND The previous thread with write access killed the lock (should be because it deleted the applicable resource)
   //     E_TIMEOUT The thread holding write access has held the lock for too long
   //     E_OK  Write access granted
   _hzfunc("hzLockRW::LockWrite") ;
   uint32_t    cont ;      //  Contention or spin count
   uint32_t    tries ;     //  Contention or spin count
   uint32_t    tid ;       //  Thread id
   uint32_t    limit ;     //  Timeout as number of tries
   if (!_hzGlobal_MT)
       return E_OK ;
   tid = pthread_self() ;
   limit = nTries < 0? 0xfffffffe:nTries*1000;
   if (m_lockval == tid)
       Fatal("Attempt by thread %u to re-lock address %p\n", tid, &m_lockval) ;
   //  Wait for lock to become free (no other threads with write access)
   for (tries = cont = 0;;)
   {
       if (m_lockval == 0xffffffff)
           return E_NOTFOUND ;
       if (m_lockval)
           { cont++ ; continue ; }
       //  Try to grab the lock
       if (!__sync_val_compare_and_swap(&m_lockval, 0,tid))
       {
           if (m_lockval == tid)
               break ;
       }
       //  Check for timeout
       tries++ ;
       if (tries > limit)
           return E_TIMEOUT ;
   }
   //  Wait for counter to drop to zero
   for (; m_counter ; cont++) ;
   return E_OK ;
}