From f376ad7f1f80bddfb754b21811d17959c45d43a4 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Sun, 16 Oct 2022 15:28:21 -0400
Subject: [PATCH] scheduler()'s intr_on() is in the wrong place, reflecting the
locking scheme from long ago.
---
kernel/proc.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/proc.c b/kernel/proc.c
index 659ca54..bc4b274 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -446,12 +446,13 @@ scheduler(void)
{
struct proc *p;
struct cpu *c = mycpu();
+
+ // Interrupts are disabled at first, but they must be
+ // enabled in order for the shell to get input.
+ intr_on();
c->proc = 0;
for(;;){
- // Avoid deadlock by ensuring that devices can interrupt.
- intr_on();
-
for(p = proc; p < &proc[NPROC]; p++) {
acquire(&p->lock);
if(p->state == RUNNABLE) {