pick_proc() called only just before returning to userspace
- new proc_is_runnable() macro to test whether process is runnable. All tests whether p_rts_flags == 0 converted to use this macro - pick_proc() calls removed from enqueue() and dequeue() - removed the test for recursive calls from pick_proc() as it certainly cannot be called recursively now - PREEMPTED flag to mark processes that were preempted by enqueueuing a higher priority process in enqueue() - enqueue_head() to enqueue PREEMPTED processes again at the head of their current priority queue - NO_QUANTUM flag to block and dequeue processes preempted by timer tick with exceeded quantum. They need to be enqueued again in schedcheck() - next_ptr global variable removed
This commit is contained in:
Tomas Hruby
parent
86cc12b9a3
commit
daf7940c69
6 changed files with 125 additions and 45 deletions
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@ -278,11 +278,8 @@ PUBLIC int ap_timer_int_handler(void)
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/* check if the process is still runnable after checking the vtimer */
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if (p->p_rts_flags == 0 && p->p_ticks_left <= 0 &&
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priv(p)->s_flags & PREEMPTIBLE) {
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proc_ptr = NULL; /* no process is scheduled for dequeue and
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enqueue */
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dequeue(p); /* take it off the queues */
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enqueue(p); /* and reinsert it again */
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proc_ptr = p; /* restore some consitent state */
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/* this dequeues the process */
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RTS_SET(p, NO_QUANTUM);
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}
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return 1;
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@ -129,6 +129,8 @@ rtsflagstr(int flags)
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FLAG(PAGEFAULT);
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FLAG(VMREQUEST);
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FLAG(VMREQTARGET);
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FLAG(PREEMPTED);
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FLAG(NO_QUANTUM);
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return str;
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}
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@ -31,7 +31,6 @@ EXTERN struct loadinfo kloadinfo; /* status of load average */
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/* Process scheduling information and the kernel reentry count. */
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EXTERN struct proc *proc_ptr; /* pointer to currently running process */
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EXTERN struct proc *next_ptr; /* next process to run after restart() */
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EXTERN struct proc *bill_ptr; /* process to bill for clock ticks */
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EXTERN struct proc *vmrestart; /* first process on vmrestart queue */
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EXTERN struct proc *vmrequest; /* first process on vmrequest queue */
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126
kernel/proc.c
126
kernel/proc.c
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@ -62,7 +62,8 @@ FORWARD _PROTOTYPE( int try_async, (struct proc *caller_ptr));
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FORWARD _PROTOTYPE( int try_one, (struct proc *src_ptr, struct proc *dst_ptr,
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int *postponed));
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FORWARD _PROTOTYPE( void sched, (struct proc *rp, int *queue, int *front));
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FORWARD _PROTOTYPE( void pick_proc, (void));
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FORWARD _PROTOTYPE( struct proc * pick_proc, (void));
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FORWARD _PROTOTYPE( void enqueue_head, (struct proc *rp));
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#define PICK_ANY 1
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#define PICK_HIGHERONLY 2
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@ -132,28 +133,47 @@ PUBLIC struct proc * schedcheck(void)
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*/
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NOREC_ENTER(schedch);
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vmassert(intr_disabled());
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if(next_ptr) {
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proc_ptr = next_ptr;
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next_ptr = NULL;
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/*
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* if the current process is still runnable check the misc flags and let
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* it run unless it becomes not runnable in the meantime
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*/
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if (proc_is_runnable(proc_ptr))
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goto check_misc_flags;
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/*
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* if a process becomes not runnable while handling the misc flags, we
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* need to pick a new one here and start from scratch. Also if the
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* current process wasn' runnable, we pick a new one here
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*/
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not_runnable_pick_new:
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if (proc_is_preempted(proc_ptr)) {
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proc_ptr->p_rts_flags &= ~PREEMPTED;
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if (proc_is_runnable(proc_ptr))
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enqueue_head(proc_ptr);
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}
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/* this enqueues the process again */
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if (proc_no_quantum(proc_ptr))
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RTS_UNSET(proc_ptr, NO_QUANTUM);
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proc_ptr = pick_proc();
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check_misc_flags:
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vmassert(proc_ptr);
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vmassert(!proc_ptr->p_rts_flags);
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vmassert(proc_is_runnable(proc_ptr));
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while (proc_ptr->p_misc_flags &
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(MF_DELIVERMSG | MF_SC_DEFER | MF_SC_TRACE | MF_SC_ACTIVE)) {
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vmassert(!next_ptr);
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vmassert(!proc_ptr->p_rts_flags);
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vmassert(proc_is_runnable(proc_ptr));
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if (proc_ptr->p_misc_flags & MF_DELIVERMSG) {
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TRACE(VF_SCHEDULING, printf("delivering to %s / %d\n",
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proc_ptr->p_name, proc_ptr->p_endpoint););
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if(delivermsg(proc_ptr) == VMSUSPEND) {
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vmassert(next_ptr);
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TRACE(VF_SCHEDULING,
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printf("suspending %s / %d\n",
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proc_ptr->p_name,
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proc_ptr->p_endpoint););
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vmassert(proc_ptr->p_rts_flags);
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vmassert(next_ptr != proc_ptr);
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vmassert(!proc_is_runnable(proc_ptr));
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}
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}
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else if (proc_ptr->p_misc_flags & MF_SC_DEFER) {
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@ -201,13 +221,12 @@ PUBLIC struct proc * schedcheck(void)
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break;
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}
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/* If proc_ptr is now descheduled,
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* continue with another process.
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/*
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* the selected process might not be runnable anymore. We have
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* to checkit and schedule another one
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*/
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if (next_ptr) {
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proc_ptr = next_ptr;
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next_ptr = NULL;
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}
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if (!proc_is_runnable(proc_ptr))
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goto not_runnable_pick_new;
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}
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TRACE(VF_SCHEDULING, printf("starting %s / %d\n",
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proc_ptr->p_name, proc_ptr->p_endpoint););
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@ -1189,13 +1208,15 @@ register struct proc *rp; /* this process is now runnable */
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CHECK_RUNQUEUES;
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#endif
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/* Now select the next process to run, if there isn't a current
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* process yet or current process isn't ready any more, or
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* it's PREEMPTIBLE.
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/*
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* enqueueing a process with a higher priority than the current one, it gets
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* preempted. The current process must be preemptible. Testing the priority
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* also makes sure that a process does not preempt itself
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*/
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if(!proc_ptr || (proc_ptr->p_priority > rp->p_priority) ||
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vmassert(proc_ptr);
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if ((proc_ptr->p_priority > rp->p_priority) &&
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(priv(proc_ptr)->s_flags & PREEMPTIBLE))
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pick_proc();
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RTS_SET(proc_ptr, PREEMPTED); /* calls dequeue() */
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#if DEBUG_SCHED_CHECK
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CHECK_RUNQUEUES;
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@ -1204,6 +1225,50 @@ register struct proc *rp; /* this process is now runnable */
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NOREC_RETURN(enqueuefunc, );
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}
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/*===========================================================================*
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* enqueue_head *
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*===========================================================================*/
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/*
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* put a process at the front of its run queue. It comes handy when a process is
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* preempted and removed from run queue to not to have a currently not-runnable
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* process on a run queue. We have to put this process back at the fron to be
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* fair
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*/
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PRIVATE void enqueue_head(struct proc *rp)
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{
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int q; /* scheduling queue to use */
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#if DEBUG_SCHED_CHECK
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if(!intr_disabled()) { minix_panic("enqueue with interrupts enabled", NO_NUM); }
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if (rp->p_ready) minix_panic("enqueue already ready process", NO_NUM);
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#endif
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/*
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* the process was runnable without its quantum expired when dequeued. A
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* process with no time left should vahe been handled else and differently
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*/
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vmassert(rp->p_ticks_left);
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vmassert(q >= 0);
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vmassert(q < IDLE_Q || rp->p_endpoint == IDLE);
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q = rp->p_priority;
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/* Now add the process to the queue. */
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if (rdy_head[q] == NIL_PROC) { /* add to empty queue */
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rdy_head[q] = rdy_tail[q] = rp; /* create a new queue */
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rp->p_nextready = NIL_PROC; /* mark new end */
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}
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else /* add to head of queue */
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rp->p_nextready = rdy_head[q]; /* chain head of queue */
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rdy_head[q] = rp; /* set new queue head */
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#if DEBUG_SCHED_CHECK
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rp->p_ready = 1;
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CHECK_RUNQUEUES;
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#endif
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}
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/*===========================================================================*
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* dequeue *
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*===========================================================================*/
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@ -1249,8 +1314,6 @@ register struct proc *rp; /* this process is no longer runnable */
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rp->p_ready = 0;
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CHECK_RUNQUEUES;
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#endif
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if (rp == proc_ptr || rp == next_ptr) /* active process removed */
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pick_proc(); /* pick new process to run */
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break;
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}
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prev_xp = *xpp; /* save previous in chain */
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@ -1299,17 +1362,15 @@ int *front; /* return: front or back */
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/*===========================================================================*
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* pick_proc *
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*===========================================================================*/
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PRIVATE void pick_proc()
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PRIVATE struct proc * pick_proc(void)
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{
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/* Decide who to run now. A new process is selected by setting 'next_ptr'.
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/* Decide who to run now. A new process is selected an returned.
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* When a billable process is selected, record it in 'bill_ptr', so that the
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* clock task can tell who to bill for system time.
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*/
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register struct proc *rp; /* process to run */
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int q; /* iterate over queues */
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NOREC_ENTER(pick);
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/* Check each of the scheduling queues for ready processes. The number of
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* queues is defined in proc.h, and priorities are set in the task table.
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* The lowest queue contains IDLE, which is always ready.
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@ -1322,14 +1383,13 @@ PRIVATE void pick_proc()
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}
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TRACE(VF_PICKPROC, printf("found %s / %d on queue %d\n",
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rp->p_name, rp->p_endpoint, q););
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next_ptr = rp; /* run process 'rp' next */
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vmassert(proc_ptr != next_ptr);
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vmassert(!next_ptr->p_rts_flags);
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vmassert(!proc_is_runnable(rp));
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if (priv(rp)->s_flags & BILLABLE)
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bill_ptr = rp; /* bill for system time */
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NOREC_RETURN(pick, );
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return rp;
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}
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minix_panic("no runnable processes", NO_NUM);
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return NULL;
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}
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/*===========================================================================*
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@ -1354,10 +1414,10 @@ timer_t *tp; /* watchdog timer pointer */
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for (rp=BEG_PROC_ADDR; rp<END_PROC_ADDR; rp++) {
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if (! isemptyp(rp)) { /* check slot use */
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if (rp->p_priority > rp->p_max_priority) { /* update priority? */
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if (rp->p_rts_flags == 0) dequeue(rp); /* take off queue */
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if (proc_is_runnable(rp)) dequeue(rp); /* take off queue */
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ticks_added += rp->p_quantum_size; /* do accounting */
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rp->p_priority -= 1; /* raise priority */
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if (rp->p_rts_flags == 0) enqueue(rp); /* put on queue */
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if (proc_is_runnable(rp)) enqueue(rp); /* put on queue */
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}
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else {
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ticks_added += rp->p_quantum_size - rp->p_ticks_left;
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@ -119,6 +119,24 @@ struct proc {
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#define VMREQUEST 0x800 /* originator of vm memory request */
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#define VMREQTARGET 0x1000 /* target of vm memory request */
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#define SYS_LOCK 0x2000 /* temporary process lock flag for systask */
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#define PREEMPTED 0x4000 /* this process was preempted by a higher
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priority process and we should pick a new one
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to run. Processes with this flag should be
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returned to the front of their current
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priority queue if they are still runnable
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before we pick a new one
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*/
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#define NO_QUANTUM 0x8000 /* process ran out of its quantum and we should
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pick a new one. Process was dequeued and
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should be enqueued at the end of some run
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queue again */
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/* A process is runnable iff p_rts_flags == 0. */
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#define rts_f_is_runnable(flg) ((flg) == 0)
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#define proc_is_runnable(p) (rts_f_is_runnable((p)->p_rts_flags))
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#define proc_is_preempted(p) ((p)->p_rts_flags & PREEMPTED)
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#define proc_no_quantum(p) ((p)->p_rts_flags & NO_QUANTUM)
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/* These runtime flags can be tested and manipulated by these macros. */
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@ -129,7 +147,7 @@ struct proc {
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#define RTS_SET(rp, f) \
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do { \
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vmassert(intr_disabled()); \
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if(!(rp)->p_rts_flags) { dequeue(rp); } \
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if(proc_is_runnable(rp)) { dequeue(rp); } \
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(rp)->p_rts_flags |= (f); \
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vmassert(intr_disabled()); \
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} while(0)
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@ -141,7 +159,9 @@ struct proc {
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vmassert(intr_disabled()); \
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rts = (rp)->p_rts_flags; \
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(rp)->p_rts_flags &= ~(f); \
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if(rts && !(rp)->p_rts_flags) { enqueue(rp); } \
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if(!rts_f_is_runnable(rts) && proc_is_runnable(rp)) { \
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enqueue(rp); \
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} \
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vmassert(intr_disabled()); \
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} while(0)
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@ -150,7 +170,7 @@ struct proc {
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do { \
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int u = 0; \
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if(!intr_disabled()) { u = 1; lock; } \
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if(!(rp)->p_rts_flags) { dequeue(rp); } \
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if(proc_is_runnable(rp)) { dequeue(rp); } \
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(rp)->p_rts_flags |= (f); \
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if(u) { unlock; } \
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} while(0)
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@ -163,7 +183,9 @@ struct proc {
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if(!intr_disabled()) { u = 1; lock; } \
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rts = (rp)->p_rts_flags; \
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(rp)->p_rts_flags &= ~(f); \
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if(rts && !(rp)->p_rts_flags) { enqueue(rp); } \
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if(!rts_f_is_runnable(rts) && proc_is_runnable(rp)) { \
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enqueue(rp); \
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} \
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if(u) { unlock; } \
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} while(0)
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@ -172,7 +194,7 @@ struct proc {
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do { \
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int u = 0; \
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if(!intr_disabled()) { u = 1; lock; } \
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if(!(rp)->p_rts_flags && (f)) { dequeue(rp); } \
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if(proc_is_runnable(rp) && (f)) { dequeue(rp); } \
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(rp)->p_rts_flags = (f); \
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if(u) { unlock; } \
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} while(0)
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@ -90,7 +90,7 @@ irq_hook_t *hook;
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sprof_info.idle_samples++;
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} else
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/* Runnable system process? */
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if (priv(proc_ptr)->s_flags & SYS_PROC && !proc_ptr->p_rts_flags) {
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if (priv(proc_ptr)->s_flags & SYS_PROC && proc_is_runnable(proc_ptr)) {
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/* Note: k_reenter is always 0 here. */
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/* Store sample (process name and program counter). */
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