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Overview
Comment:Fix deadlock problem in the unix mutex. Ticket #1672. (CVS 3071)
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SHA1:a6c30be214bb575f9ecfa299b7a597d21e3d3aca
User & Date: drh 2006-02-10 04:33:12
Context
2006-02-10
07:07
Fix the origin APIs so that they correctly handle views and subqueries that cannot be flattened. (CVS 3072) check-in: 5e8611e1 user: danielk1977 tags: trunk
04:33
Fix deadlock problem in the unix mutex. Ticket #1672. (CVS 3071) check-in: a6c30be2 user: drh tags: trunk
03:06
Add a symbol P3_TRANSIENT to pass to VdbeSetColName() to make it copy the string parameter up to the first 0 byte. (CVS 3070) check-in: 6ebb8f9b user: danielk1977 tags: trunk
Changes
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Changes to src/os_unix.c.

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#else
  sleep((ms+999)/1000);
  return 1000*((ms+999)/1000);
#endif
}

/*
** Static variables used for thread synchronization
















*/
static int inMutex = 0;
#ifdef SQLITE_UNIX_THREADS
static pthread_t mutexOwner;

static pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t mutex2 = PTHREAD_MUTEX_INITIALIZER;
#endif

/*
** The following pair of routine implement mutual exclusion for
** multi-threaded processes.  Only a single thread is allowed to
** executed code that is surrounded by EnterMutex() and LeaveMutex().
**
................................................................................
** SQLite uses only a single Mutex.  There is not much critical
** code and what little there is executes quickly and without blocking.
**
** As of version 3.3.2, this mutex must be recursive.
*/
void sqlite3UnixEnterMutex(){
#ifdef SQLITE_UNIX_THREADS
  pthread_mutex_lock(&mutex1);



  if( inMutex==0 ){

    pthread_mutex_lock(&mutex2);
    mutexOwner = pthread_self();

  }

  pthread_mutex_unlock(&mutex1);
#endif
  inMutex++;

}
void sqlite3UnixLeaveMutex(){
  assert( inMutex>0 );
#ifdef SQLITE_UNIX_THREADS
  assert( pthread_equal(mutexOwner, pthread_self()) );
  pthread_mutex_lock(&mutex1);
  inMutex--;

  if( inMutex==0 ){


    pthread_mutex_unlock(&mutex2);
  }
  pthread_mutex_unlock(&mutex1);
#else
  inMutex--;
#endif
}

/*
** Return TRUE if the mutex is currently held.
**
** If the thisThreadOnly parameter is true, return true only if the
** calling thread holds the mutex.  If the parameter is false, return
** true if any thread holds the mutex.
*/
int sqlite3UnixInMutex(int thisThreadOnly){
#ifdef SQLITE_UNIX_THREADS
  return inMutex>0 && 

           (thisThreadOnly==0 || pthread_equal(mutexOwner, pthread_self()));


#else
  return inMutex>0;
#endif
}

/*
** Remember the number of thread-specific-data blocks allocated.







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#else
  sleep((ms+999)/1000);
  return 1000*((ms+999)/1000);
#endif
}

/*
** Static variables used for thread synchronization.
**
** inMutex      the nesting depth of the recursive mutex.  The thread
**              holding mutexMain can read this variable at any time.
**              But is must hold mutexAux to change this variable.  Other
**              threads must hold mutexAux to read the variable.
**
** mutexOwner   The thread id of the thread holding mutexMain.  Same
**              access rules as for inMutex.
**
** mutexOwnerValid   True if the value in mutexOwner is valid.  
**
** mutexMain    The main mutex.  Hold this mutex in order to get exclusive
**              access to SQLite data structures.
**
** mutexAux     An auxiliary mutex needed to access variables defined above.
**
*/
static int inMutex = 0;
#ifdef SQLITE_UNIX_THREADS
static pthread_t mutexOwner;          /* Thread holding the mutex */
static int mutexOwnerValid = 0;       /* True if mutexOwner is valid */
static pthread_mutex_t mutexMain = PTHREAD_MUTEX_INITIALIZER; /* The mutex */
static pthread_mutex_t mutexAux = PTHREAD_MUTEX_INITIALIZER;  /* Aux mutex */
#endif

/*
** The following pair of routine implement mutual exclusion for
** multi-threaded processes.  Only a single thread is allowed to
** executed code that is surrounded by EnterMutex() and LeaveMutex().
**
................................................................................
** SQLite uses only a single Mutex.  There is not much critical
** code and what little there is executes quickly and without blocking.
**
** As of version 3.3.2, this mutex must be recursive.
*/
void sqlite3UnixEnterMutex(){
#ifdef SQLITE_UNIX_THREADS
  pthread_mutex_lock(&mutexAux);
  if( !mutexOwnerValid || !pthread_equal(mutexOwner, pthread_self()) ){
    pthread_mutex_unlock(&mutexAux);
    pthread_mutex_lock(&mutexMain);
    assert( inMutex==0 );
    assert( !mutexOwnerValid );
    pthread_mutex_lock(&mutexAux);
    mutexOwner = pthread_self();
    mutexOwnerValid = 1;
  }
  inMutex++;
  pthread_mutex_unlock(&mutexAux);
#else
  inMutex++
#endif
}
void sqlite3UnixLeaveMutex(){
  assert( inMutex>0 );
#ifdef SQLITE_UNIX_THREADS

  pthread_mutex_lock(&mutexAux);
  inMutex--;
  assert( pthread_equal(mutexOwner, pthread_self()) );
  if( inMutex==0 ){
    assert( mutexOwnerValid );
    mutexOwnerValid = 0;
    pthread_mutex_unlock(&mutexMain);
  }
  pthread_mutex_unlock(&mutexAux);
#else
  inMutex--;
#endif
}

/*
** Return TRUE if the mutex is currently held.
**
** If the thisThrd parameter is true, return true only if the
** calling thread holds the mutex.  If the parameter is false, return
** true if any thread holds the mutex.
*/
int sqlite3UnixInMutex(int thisThrd){
#ifdef SQLITE_UNIX_THREADS
  int rc;
  pthread_mutex_lock(&mutexAux);
  rc = inMutex>0 && (thisThrd==0 || pthread_equal(mutexOwner,pthread_self()));
  pthread_mutex_unlock(&mutexAux);
  return rc;
#else
  return inMutex>0;
#endif
}

/*
** Remember the number of thread-specific-data blocks allocated.