kernel/system/do_nice.c

   1 /* The kernel call implemented in this file:
   2  *   m_type:    SYS_NICE
   3  *
   4  * The parameters for this kernel call are:
   5  *    m1_i1:    PR_ENDPT        process number to change priority
   6  *    m1_i2:    PR_PRIORITY     the new priority
   7  */
   8
   9 #include "../system.h"
  10 #include <sys/resource.h>
  11
  12 #if USE_NICE
  13
  14 /*===========================================================================*
  15  *                                do_nice                                    *
  16  *===========================================================================*/
  17 PUBLIC int do_nice(struct proc * caller, message * m_ptr)
  18 {
  19 /* Change process priority or stop the process. */
  20   int proc_nr, pri, new_q ;
  21   register struct proc *rp;
  22
  23   /* Extract the message parameters and do sanity checking. */
  24   if(!isokendpt(m_ptr->PR_ENDPT, &proc_nr)) return EINVAL;
  25   if (iskerneln(proc_nr)) return(EPERM);
  26   pri = m_ptr->PR_PRIORITY;
  27   rp = proc_addr(proc_nr);
  28
  29   /* The value passed in is currently between PRIO_MIN and PRIO_MAX.
  30    * We have to scale this between MIN_USER_Q and MAX_USER_Q to match
  31    * the kernel's scheduling queues.
  32    */
  33   if (pri < PRIO_MIN || pri > PRIO_MAX) return(EINVAL);
  34
  35   new_q = MAX_USER_Q + (pri-PRIO_MIN) * (MIN_USER_Q-MAX_USER_Q+1) /
  36       (PRIO_MAX-PRIO_MIN+1);
  37   if (new_q < MAX_USER_Q) new_q = MAX_USER_Q;   /* shouldn't happen */
  38   if (new_q > MIN_USER_Q) new_q = MIN_USER_Q;   /* shouldn't happen */
  39
  40   /* Make sure the process is not running while changing its priority.
  41    * Put the process back in its new queue if it is runnable.
  42    */
  43   RTS_LOCK_SET(rp, RTS_SYS_LOCK);
  44   rp->p_max_priority = rp->p_priority = new_q;
  45   RTS_LOCK_UNSET(rp, RTS_SYS_LOCK);
  46
  47   return(OK);
  48 }
  49
  50 #endif /* USE_NICE */
  51