minix/kernel/system/do_nice.c
2006-03-10 16:10:05 +00:00

61 lines
1.8 KiB
C

/* The kernel call implemented in this file:
* m_type: SYS_NICE
*
* The parameters for this kernel call are:
* m1_i1: PR_ENDPT process number to change priority
* m1_i2: PR_PRIORITY the new priority
*/
#include "../system.h"
#include <minix/type.h>
#include <sys/resource.h>
#if USE_NICE
/*===========================================================================*
* do_nice *
*===========================================================================*/
PUBLIC int do_nice(message *m_ptr)
{
/* Change process priority or stop the process. */
int proc_nr, pri, new_q ;
register struct proc *rp;
/* Extract the message parameters and do sanity checking. */
if(!isokendpt(m_ptr->PR_ENDPT, &proc_nr)) return EINVAL;
if (iskerneln(proc_nr)) return(EPERM);
pri = m_ptr->PR_PRIORITY;
rp = proc_addr(proc_nr);
if (pri == PRIO_STOP) {
/* Take process off the scheduling queues. */
lock_dequeue(rp);
rp->p_rts_flags |= NO_PRIORITY;
return(OK);
}
else if (pri >= PRIO_MIN && pri <= PRIO_MAX) {
/* The value passed in is currently between PRIO_MIN and PRIO_MAX.
* We have to scale this between MIN_USER_Q and MAX_USER_Q to match
* the kernel's scheduling queues.
*/
new_q = MAX_USER_Q + (pri-PRIO_MIN) * (MIN_USER_Q-MAX_USER_Q+1) /
(PRIO_MAX-PRIO_MIN+1);
if (new_q < MAX_USER_Q) new_q = MAX_USER_Q; /* shouldn't happen */
if (new_q > MIN_USER_Q) new_q = MIN_USER_Q; /* shouldn't happen */
/* Make sure the process is not running while changing its priority.
* Put the process back in its new queue if it is runnable.
*/
lock_dequeue(rp);
rp->p_max_priority = rp->p_priority = new_q;
if (! rp->p_rts_flags) lock_enqueue(rp);
return(OK);
}
return(EINVAL);
}
#endif /* USE_NICE */