From 4a88273db5df00c5d3397ad5bcef50eb68f4bef8 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Mon, 17 Oct 2022 04:07:24 -0400
Subject: [PATCH] oops. scheduler() inherits the interrupt status of the most
recent process to run, so it must explicitly turn them on again. It would be
better if cpu->intena were really thread->intena.
---
kernel/proc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/proc.c b/kernel/proc.c
index bc4b274..809d112 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -447,12 +447,12 @@ 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(;;){
+ // The most recent process to run may have had interrupts
+ // turned off; turn them on to avoid deadlock.
+ intr_on();
+
for(p = proc; p < &proc[NPROC]; p++) {
acquire(&p->lock);
if(p->state == RUNNABLE) {