rom/exec/settaskpri.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Change the priority of a task.
   6     Lang: english
   7 */
   8
   9 #include <exec/execbase.h>
  10 #include <aros/libcall.h>
  11 #include <proto/exec.h>
  12
  13 /*****************************************************************************
  14
  15     NAME */
  16
  17         AROS_LH2(BYTE, SetTaskPri,
  18
  19 /*  SYNOPSIS */
  20         AROS_LHA(struct Task *, task,      A1),
  21         AROS_LHA(LONG,          priority,  D0),
  22
  23 /*  LOCATION */
  24         struct ExecBase *, SysBase, 50, Exec)
  25
  26 /*  FUNCTION
  27         Change the priority of a given task. As a general rule the higher
  28         the priority the more CPU time a task gets. Useful values are within
  29         -127 to 5.
  30
  31     INPUTS
  32         task     - Pointer to task structure.
  33         priority - New priority of the task.
  34
  35     RESULT
  36         Old task priority.
  37
  38     NOTES
  39
  40     EXAMPLE
  41
  42     BUGS
  43
  44     SEE ALSO
  45
  46     INTERNALS
  47
  48     HISTORY
  49
  50 ******************************************************************************/
  51 {
  52     AROS_LIBFUNC_INIT
  53
  54     BYTE old;
  55
  56     /* Always Disable() when doing something with task lists. */
  57     Disable();
  58
  59     /* Get returncode */
  60     old=task->tc_Node.ln_Pri;
  61
  62     /* Set new value. */
  63     task->tc_Node.ln_Pri=priority;
  64
  65     /* Check if the task is willing to run. */
  66     if(task->tc_State!=TS_WAIT)
  67     {
  68         /* If it is in the ready list remove and reinsert it. */
  69         if(task->tc_State==TS_READY)
  70         {
  71             Remove(&task->tc_Node);
  72             Enqueue(&SysBase->TaskReady,&task->tc_Node);
  73         }
  74
  75         /*
  76             I could check the task priorities here to determine if
  77             the following is really necessary, but OTOH priority
  78             changes are rare and the hassle isn't really worth it.
  79
  80             This should be reconsidered, because of Executive [ldp].
  81         */
  82         Reschedule();
  83     }
  84
  85     /* All done. */
  86     Enable();
  87     return old;
  88
  89     AROS_LIBFUNC_EXIT
  90 } /* SetTaskPri */