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tis(3)
NAME
  tis, tis_intro - Introduction to Thread-Independent Services (tis)

DESCRIPTION
  Thread-independent services (tis) routines comprise a DIGITAL-proprietary
  interface to the DECthreads multitasking library.  The tis interface
  provides services that assist with the development of thread-safe
  libraries.

  Thread synchronization can involve significant run-time cost, which is
  undesirable in a nonthreaded environment.  In the nonthreaded environment,
  the tis interface enables you to build thread-safe libraries that are
  efficient, yet provide the necessary synchronization when called from a
  threaded environment.

  When threads are not active within the process, tis routines execute only
  the minimum steps necessary: code running in a nonthreaded environment is
  not burdened by the run-time synchronization that is necessary when the
  same code is run in a threaded environment.  When threads are active, tis
  routines provide the necessary thread-safe synchronization.

  The tis objects created using this interface are fully interchangeable with
  DECthreads Pthreads (POSIX 1003.1c) objects.	So, a mutex can be created by
  using static initialization (or using tis_mutex_init(3)) and can be locked,
  the DECthreads core library (libpthread.so) subsequently activated, and the
  mutex unlocked.  Keys created by tis_key_create(3) are valid when a
  threaded run-time environment is loaded.

  Note that errno is NOT used by the tis routines.  To indicate errors, the
  tis routines return integer values indicating the type of error.

  In a nonthreaded environment, condition variables should not be used to
  guard operations (for example, with tis_cond_wait(3)).  In a threaded
  environment, the guidelines for using the DECthreads Pthread routines also
  pertain to the use of the corresponding tis routine.

  The tis routines can be classified into the following associated groups:

    ·  General routines

    ·  Thread cancelation routines

    ·  Thread-specific data key routines

    ·  Mutex routines

    ·  Condition variable routines

    ·  Read-write lock routines



  General Routines


  tis_once	Calls a one-time initialization routine that can be executed.

  tis_self	Obtains the identifier of the calling thread.


  Thread Cancelation Routines


  tis_setcancelstate
		Changes the calling thread's cancelability state.

  tis_testcancel
		Creates a cancelation point in the calling thread.


  Thread-Specific Data Key Routines


  tis_getspecific
		Obtains the data associated with the specified thread-
		specific data key.

  tis_key_create
		Generates a unique thread-specific data key.

  tis_key_delete
		Deletes a thread-specific data key.

  tis_setspecific
		Sets the value associated with the specified thread-specific
		key.


  Mutex Routines


  tis_lock_global
		Locks the DECthreads global mutex.

  tis_mutex_destroy
		Destroys the specified tis mutex object.

  tis_mutex_init
		Initializes a tis mutex object.

  tis_mutex_lock
		Locks the specified tis mutex if not already locked.

  tis_mutex_trylock
		Tries to lock the specified tis mutex.

  tis_mutex_unlock
		Unlocks the specified tis mutex.

  tis_unlock_global
		Unlocks the DECthreads global mutex.


  Condition Variable Routines


  tis_cond_broadcast
		Wakes all threads waiting on the specified condition
		variable.

  tis_cond_destroy
		Destroys the specified condition variable object.

  tis_cond_init Initializes a condition variable object.

  tis_cond_signal
		Wakes at least one thread that is waiting on the specified
		condition variable.

  tis_cond_wait Causes the calling thread to wait for the specified condition
		variable to be signaled or broadcasted.


  Read-Write Lock Routines


  tis_read_lock Acquires the specified read-write lock for read access.

  tis_read_trylock
		Attempts to acquire the specified read-write lock for read
		access; returns immediately if already locked.

  tis_read_unlock
		Unlocks the specified read-write lock already acquired for
		read access.

  tis_rwlock_destroy
		Destroys the specified read-write lock object.

  tis_rwlock_init
		Initializes a read-write lock object.

  tis_write_lock
		Acquires the specified read-write lock for write access.

  tis_write_trylock
		Attempts to acquire the specified read-write lock for write
		access; returns immediately if already locked.

  tis_write_unlock
		Unlocks the specified read-write lock already acquired for
		write access.