52 lines
1.5 KiB
C
52 lines
1.5 KiB
C
/* The system call implemented in this file:
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* m_type: SYS_NICE
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*
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* The parameters for this system call are:
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* m1_i1: PR_PROC_NR process number to change priority
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* m1_i2: PR_PRIORITY the new priority
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*/
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#include "../system.h"
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#include <minix/type.h>
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#include <sys/resource.h>
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#if USE_NICE
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/*===========================================================================*
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* do_nice *
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*===========================================================================*/
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PUBLIC int do_nice(message *m_ptr)
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{
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int proc_nr, pri, new_q ;
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register struct proc *rp;
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/* Extract the message parameters and do sanity checking. */
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proc_nr = m_ptr->PR_PROC_NR;
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if (! isokprocn(proc_nr)) return(EINVAL);
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if (iskerneln(proc_nr)) return(EPERM);
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pri = m_ptr->PR_PRIORITY;
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if (pri < PRIO_MIN || pri > PRIO_MAX) return(EINVAL);
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/* The priority is currently between PRIO_MIN and PRIO_MAX. We have to
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* scale this between MIN_USER_Q and MAX_USER_Q.
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*/
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new_q = MAX_USER_Q + (pri-PRIO_MIN) * (MIN_USER_Q-MAX_USER_Q+1) /
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(PRIO_MAX-PRIO_MIN+1);
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if (new_q < MAX_USER_Q) new_q = MAX_USER_Q; /* shouldn't happen */
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if (new_q > MIN_USER_Q) new_q = MIN_USER_Q; /* shouldn't happen */
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/* Make sure the process is not running while changing its priority; the
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* max_priority is the base priority. Put the process back in its new
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* queue if it is runnable.
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*/
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rp = proc_addr(proc_nr);
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lock_dequeue(rp);
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rp->p_max_priority = rp->p_priority = new_q;
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if (! rp->p_rts_flags) lock_enqueue(rp);
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return(OK);
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}
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#endif /* USE_NICE */
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