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Don't start processes at the end of the proc table

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This commit is contained in:
Frans Kaashoek 2019-07-02 13:55:52 -04:00
parent da51735980
commit 37ac6f8f4f
1 changed files with 8 additions and 6 deletions
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12
kernel/proc.c
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@ -372,12 +372,14 @@ wait(void)
} }
// Loop over process table looking for process to run. // Loop over process table looking for process to run.
struct proc *find_runnable() { struct proc *find_runnable(int start) {
struct proc *p; struct proc *p;
acquire(&ptable.lock); acquire(&ptable.lock);
for(p = ptable.proc; p < &ptable.proc[NPROC]; p++) { for(int i = start; i < start+NPROC; i++) {
p = &ptable.proc[i % NPROC];
acquire(&p->lock); acquire(&p->lock);
if(p->state == RUNNABLE) { if(p->state == RUNNABLE) {
p->state = RUNNING;
release(&ptable.lock); release(&ptable.lock);
return p; return p;
} }
@ -400,19 +402,19 @@ scheduler(void)
{ {
struct proc *p; struct proc *p;
struct cpu *c = mycpu(); struct cpu *c = mycpu();
int next;
c->proc = 0; c->proc = 0;
for(;;){ for(;;){
// Enable interrupts on this processor. // Enable interrupts on this processor.
intr_on(); intr_on();
if((p = find_runnable()) != 0){ if((p = find_runnable(next)) != 0) {
next = (next + 1) & NPROC;
// Switch to chosen process. It is the process's job // Switch to chosen process. It is the process's job
// to release its lock and then reacquire it // to release its lock and then reacquire it
// before jumping back to us. // before jumping back to us.
c->proc = p; c->proc = p;
p->state = RUNNING;
swtch(&c->scheduler, &p->context); swtch(&c->scheduler, &p->context);
// Process is done running for now. // Process is done running for now.