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74 lines
2.1 KiB
74 lines
2.1 KiB
/*
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* implementing the scheduler
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*/
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#include "sched.h"
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#include "spike_interface/spike_utils.h"
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process* ready_queue_head = NULL;
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//
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// insert a process, proc, into the END of ready queue.
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//
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void insert_to_ready_queue( process* proc ) {
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sprint( "going to insert process %d to ready queue.\n", proc->pid );
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// if the queue is empty in the beginning
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if( ready_queue_head == NULL ){
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proc->status = READY;
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proc->queue_next = NULL;
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ready_queue_head = proc;
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return;
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}
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// ready queue is not empty
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process *p;
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// browse the ready queue to see if proc is already in-queue
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for( p=ready_queue_head; p->queue_next!=NULL; p=p->queue_next )
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if( p == proc ) return; //already in queue
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// p points to the last element of the ready queue
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if( p==proc ) return;
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p->queue_next = proc;
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proc->status = READY;
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proc->queue_next = NULL;
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return;
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}
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//
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// choose a proc from the ready queue, and put it to run.
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// note: schedule() does not take care of previous current process. If the current
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// process is still runnable, you should place it into the ready queue (by calling
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// ready_queue_insert), and then call schedule().
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//
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extern process procs[NPROC];
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void schedule() {
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if ( !ready_queue_head ){
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// by default, if there are no ready process, and all processes are in the status of
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// FREE and ZOMBIE, we should shutdown the emulated RISC-V machine.
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int should_shutdown = 1;
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for( int i=0; i<NPROC; i++ )
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if( (procs[i].status != FREE) && (procs[i].status != ZOMBIE) ){
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should_shutdown = 0;
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sprint( "ready queue empty, but process %d is not in free/zombie state:%d\n",
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i, procs[i].status );
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}
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if( should_shutdown ){
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sprint( "no more ready processes, system shutdown now.\n" );
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shutdown( 0 );
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}else{
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panic( "Not handled: we should let system wait for unfinished processes.\n" );
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}
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}
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current = ready_queue_head;
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assert( current->status == READY );
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ready_queue_head = ready_queue_head->queue_next;
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current->status = RUNNING;
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sprint( "going to schedule process %d to run.\n", current->pid );
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switch_to( current );
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}
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