Manual Pages for UNIX Operating System command usage for man schedctl_lookup

Standard C Library Functions                    schedctl_init(3C)



NAME
     schedctl_init,        schedctl_lookup,        schedctl_exit,
     schedctl_start, schedctl_stop - preemption control

SYNOPSIS
     cc [ flag... ] file...  [ library... ]
     #include 

     schedctl_t *schedctl_init(void);


     schedctl_t *schedctl_lookup(void);


     void schedctl_exit(void);


     void schedctl_start(schedctl_t *ptr);


     void schedctl_stop(schedctl_t *ptr);


DESCRIPTION
     These functions provide limited control over the  scheduling
     of a thread (see threads(5)). They allow a running thread to
     give a hint to the kernel that preemptions  of  that  thread
     should  be  avoided. The most likely use for these functions
     is to block preemption while holding  a  spinlock.  Improper
     use of this facility, including attempts to block preemption
     for sustained periods of time, may result in reduced perfor-
     mance.


     The schedctl_init() function initializes preemption  control
     for  the  calling thread and returns a pointer used to refer
     to the data. If schedctl_init() is called more than once  by
     the  same  thread, the most recently returned pointer is the
     only valid one.


     The schedctl_lookup() function returns the  currently  allo-
     cated  preemption  control  data associated with the calling
     thread that was previously returned by schedctl_init(). This
     can  be useful in programs where it is difficult to maintain
     local state for each thread.


     The schedctl_exit() function removes the preemption  control
     data associated with the calling thread.





SunOS 5.11          Last change: 28 May 2003                    1






Standard C Library Functions                    schedctl_init(3C)



     The schedctl_start()  macro  gives  a  hint  to  the  kernel
     scheduler  that  preemption should be avoided on the current
     thread. The pointer passed to the macro must be the same  as
     the  pointer  returned by the call to schedctl_init() by the
     current thread. The  behavior  of  the  program  when  other
     values are passed is undefined.


     The schedctl_stop() macro removes the hint that was  set  by
     schedctl_start().  As  with  schedctl_start(),  the  pointer
     passed to the macro must be the same as the pointer returned
     by the call to schedctl_init() by the current thread.


     The schedctl_start() and schedctl_stop() macros are intended
     to  be  used to bracket short critical sections, such as the
     time spent holding a spinlock.  Other  uses,  including  the
     failure   to   call   schedctl_stop()   soon  after  calling
     schedctl_start(), might result in poor performance.

RETURN VALUES
     The  schedctl_init()  function  returns  a  pointer   to   a
     schedctl_t  structure  if the initialization was successful,
     or NULL otherwise. The schedctl_lookup() function returns  a
     pointer  to  a  schedctl_t  structure  if  the data for that
     thread was found, or NULL otherwise.

ERRORS
     No errors are returned.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO
     priocntl(1), exec(2), fork(2),  priocntl(2),  attributes(5),
     threads(5)

NOTES
     Preemption control is intended for use by threads  belonging
     to  the  time-sharing  (TS),  interactive  (IA),  fair-share



SunOS 5.11          Last change: 28 May 2003                    2






Standard C Library Functions                    schedctl_init(3C)



     (FSS), and fixed-priority (FX) scheduling classes.  If  used
     by  threads  in  other scheduling classes, such as real-time
     (RT), no errors will be returned  but  schedctl_start()  and
     schedctl_stop() will not have any effect.


     The data used for preemption control are not copied  in  the
     child  of  a  fork(2). Thus, if a process containing threads
     using preemption control calls fork and the child  does  not
     immediately call exec(2), each thread in the child must call
     schedctl_init()  again  prior  to   any   future   uses   of
     schedctl_start()  and schedctl_stop(). Failure to do so will
     result in undefined behavior.










































SunOS 5.11          Last change: 28 May 2003                    3