rom/exec/settaskpri.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Change the priority of a task.
   6     Lang: english
   7 */
   8 #include <exec/execbase.h>
   9 #include <aros/libcall.h>
  10 #include <proto/exec.h>
  11
  12 /*****************************************************************************
  13
  14     NAME */
  15
  16         AROS_LH2(BYTE, SetTaskPri,
  17
  18 /*  SYNOPSIS */
  19         AROS_LHA(struct Task *, task,      A1),
  20         AROS_LHA(LONG,          priority,  D0),
  21
  22 /*  LOCATION */
  23         struct ExecBase *, SysBase, 50, Exec)
  24
  25 /*  FUNCTION
  26         Change the priority of a given task. As a general rule the higher
  27         the priority the more CPU time a task gets. Useful values are within
  28         -127 to 5.
  29
  30     INPUTS
  31         task     - Pointer to task structure.
  32         priority - New priority of the task.
  33
  34     RESULT
  35         Old task priority.
  36
  37     NOTES
  38
  39     EXAMPLE
  40
  41     BUGS
  42
  43     SEE ALSO
  44
  45     INTERNALS
  46
  47 ******************************************************************************/
  48 {
  49     AROS_LIBFUNC_INIT
  50
  51     BYTE old;
  52
  53     /* Always Disable() when doing something with task lists. */
  54     Disable();
  55
  56     /* Get returncode */
  57     old=task->tc_Node.ln_Pri;
  58
  59     /* Set new value. */
  60     task->tc_Node.ln_Pri=priority;
  61
  62     /* Check if the task is willing to run. */
  63     if(task->tc_State!=TS_WAIT)
  64     {
  65         /* If it is in the ready list remove and reinsert it. */
  66         if(task->tc_State==TS_READY)
  67         {
  68             Remove(&task->tc_Node);
  69             Enqueue(&SysBase->TaskReady,&task->tc_Node);
  70         }
  71
  72         /*
  73             I could check the task priorities here to determine if
  74             the following is really necessary, but OTOH priority
  75             changes are rare and the hassle isn't really worth it.
  76
  77             This should be reconsidered, because of Executive [ldp].
  78         */
  79
  80         /* Are taskswitches allowed? */
  81         if(SysBase->TDNestCnt>=0||SysBase->IDNestCnt>0)
  82             /* No. Store it for later. */
  83             SysBase->AttnResched|=0x80;
  84         else
  85         {
  86             /* Switches are allowed. Move the current task away. */
  87             SysBase->ThisTask->tc_State=TS_READY;
  88             Enqueue(&SysBase->TaskReady,&SysBase->ThisTask->tc_Node);
  89
  90             /* And force a reschedule. */
  91             Switch();
  92         }
  93     }
  94
  95     /* All done. */
  96     Enable();
  97     return old;
  98     AROS_LIBFUNC_EXIT
  99 } /* SetTaskPri */