From 4087a6e7fc773ba4eb217dfc196dfe1eee84b25d Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Wed, 10 Aug 2022 20:35:42 -0400
Subject: Read and write p->killed using atomics

---
 kernel/proc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'kernel/proc.c')

diff --git a/kernel/proc.c b/kernel/proc.c
index 2d0ffa1..221f0f8 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -422,7 +422,7 @@ wait(uint64 addr)
     }
 
     // No point waiting if we don't have any children.
-    if(!havekids || p->killed){
+    if(!havekids || __sync_add_and_fetch(&p->killed, 0)){
       release(&wait_lock);
       return -1;
     }
@@ -588,7 +588,7 @@ kill(int pid)
   for(p = proc; p < &proc[NPROC]; p++){
     acquire(&p->lock);
     if(p->pid == pid){
-      p->killed = 1;
+      __sync_bool_compare_and_swap(&p->killed, 0, 1);
       if(p->state == SLEEPING){
         // Wake process from sleep().
         p->state = RUNNABLE;
-- 
cgit v1.2.3