minix/kernel/system/do_nice.c
2005-07-19 14:03:21 +00:00

50 lines
1.5 KiB
C

/* The system call implemented in this file:
* m_type: SYS_NICE
*
* The parameters for this system call are:
* m1_i1: PR_PROC_NR 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)
{
int proc_nr, pri, new_q ;
register struct proc *rp;
/* Extract the message parameters and do sanity checking. */
proc_nr = m_ptr->PR_PROC_NR;
if (! isokprocn(proc_nr)) return(EINVAL);
pri = m_ptr->PR_PRIORITY;
if (pri < PRIO_MIN || pri > PRIO_MAX) return(EINVAL);
/* The priority is currently between PRIO_MIN and PRIO_MAX. We have to
* scale this between MIN_USER_Q and MAX_USER_Q.
*/
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; the
* max_priority is the base priority. Put the process back in its new
* queue if it is runnable.
*/
rp = proc_addr(proc_nr);
lock_unready(rp);
rp->p_max_priority = rp->p_priority = new_q;
if (! rp->p_rts_flags) lock_ready(rp);
return(OK);
}
#endif /* USE_NICE */