pthread_mutexattr_setprioceiling man page on HP-UX

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pthread_mutexattr_getprotocol(3T)	     pthread_mutexattr_getprotocol(3T)

NAME
       pthread_mutexattr_getprotocol(),	      pthread_mutexattr_setprotocol(),
       pthread_mutexattr_getprioceiling(),  pthread_mutexattr_setprioceiling()
       - get and set the protocol and prioceiling attributes

SYNOPSIS

PARAMETERS
	      attr	Pointer	  to   the   mutex   attributes	 object	 whose
			attributes are to be set/retrieved.

	      prioceiling
			This parameter either specifies the new value  of  the
			prioceiling  attribute (set function) or points to the
			memory location where  the  prioceiling	 attribute  of
			attr is to be returned (get function).

	      protocol	This  parameter	 either specifies the new value of the
			protocol attribute (set function)  or  points  to  the
			memory	location  where the protocol attribute of attr
			is to be returned (get function).

DESCRIPTION
       Be sure to check for the definitions of and before  using  these	 func‐
       tions.  Not all systems will support these functions.

       The  attributes	object attr must have previously been initialized with
       the function before these functions are called.

   ATTRIBUTE: protocol
       Mutexes can be initialized with a priority protocol to  help  avoid  or
       minimize	 the  priority inversion that can be caused by locked mutexes.
       The protocol attribute in a mutex attributes object describes the  pri‐
       ority  protocol	to  be used when the mutex is locked by a thread.  The
       legal values for the protocol attribute are:

	      A thread's scheduling priority is not changed when it locks this
	      type of mutex.

	      These types of mutexes have an associated priority value in the
		     prioceiling  attribute.   When  a thread locks a mutex of
		     this type, its scheduling priority will be changed to  be
		     the  value	 contained  in the prioceiling attribute.  The
		     value of prioceiling must	be  higher  than  the  locking
		     thread's	scheduling   priority.	  When	the  mutex  is
		     unlocked, the thread's previous scheduling priority  will
		     be restored.

		     If a thread owns several mutexes of this type, its sched‐
		     uling priority will be changed to the higher of  all  the
		     prioceiling  attributes for all mutexes of this type that
		     it owns.

	      When a thread must block waiting for a mutex of this  type,  the
	      system
		     will  change  the	scheduling priority of the thread that
		     owns the mutex to be the higher of its  own  priority  or
		     the  priority  of	the highest priority thread blocked on
		     the mutex.	 When the mutex is unlocked, the thread's pre‐
		     vious scheduling priority will be restored.

       If  a  thread  owns  one	 or more mutexes having the protocol attribute
       value of or the thread will not be moved to the tail  of	 its  priority
       list  if	 its  original	priority  is  changed  or  when it unlocks the
       mutex(es).

       If a thread owns mutexes of different priority protocols, it will  exe‐
       cute at the highest of the priorities that would be obtained by each of
       these protocols.	 If this thread becomes blocked on another mutex,  the
       priority behavior is recursive and is passed on to the thread that owns
       the mutex on which this thread is blocked.

       POSIX.1c does not define a default value for the protocol attribute. On
       HP-UX, the default value is

       is  used	 to  set  the protocol attribute in the initialized attributes
       object attr.  The new value of the protocol attribute of attr is set to
       the value specified in the protocol parameter.

       retrieves the value of the protocol attribute from the mutex attributes
       object attr.  The value of the protocol attribute of attr  is  returned
       in the protocol parameter.

   ATTRIBUTE: prioceiling
       If  the	protocol  attribute  has  a value of the prioceiling attribute
       indicates the priority ceiling of the mutex.  Otherwise, this attribute
       is not used when the mutex is initialized.

       The priority values that are valid for this attribute are the same val‐
       ues that are valid for the scheduling policy.

       POSIX.1c does not define a default value for the prioceiling attribute.
       On  HP-UX,  the	default	 value	is  the minimum priority value for the
       scheduling policy.

       is used to set the prioceiling attribute in the initialized  attributes
       object attr.  The new value of the prioceiling attribute of attr is set
       to the value specified in the prioceiling parameter.

       retrieves the  value  of	 the  prioceiling  attribute  from  the	 mutex
       attributes object attr.	The value of the prioceiling attribute of attr
       is returned in the prioceiling parameter.

RETURN VALUE
       Upon successful completion, and return zero. Otherwise, an error number
       is returned to indicate the error (the variable is not set).

ERRORS
       If any of the following occur, the and functions return the correspond‐
       ing error number:

	      is not defined and these functions are not supported.

	      protocol	     contains an unsupported value.

       For each of the following conditions, if the condition is detected, the
       and functions return the corresponding error number:

	      The value specified by
			     attr, prioceiling, or protocol is invalid.

	      The  caller  does	 not have the appropriate privilege to set the
	      priority
			     ceiling or priority  protocol  to	the  specified
			     values.

AUTHOR
       and were derived from the IEEE POSIX P1003.1c standard.

SEE ALSO
       pthread_create(3T), pthread_mutexattr_init(3T), pthread_mutex_init(3T).

STANDARDS CONFORMANCE
				Pthread Librapthread_mutexattr_getprotocol(3T)
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