diff --git a/kernel/proc/proc.c b/kernel/proc/proc.c
index 7004043..105229d 100644
--- a/kernel/proc/proc.c
+++ b/kernel/proc/proc.c
@@ -239,7 +239,9 @@ void proc_sched(void *cpustate) {
 }
 
 void proc_kill(Proc *proc) {
+  spinlock_acquire(&PROCS.spinlock);
   proc->state = PROC_ZOMBIE;
+  spinlock_release(&PROCS.spinlock);
 }
 
 void proc_killself(void) {
diff --git a/kernel/syscall/proc.c b/kernel/syscall/proc.c
index 51751d0..18dd392 100644
--- a/kernel/syscall/proc.c
+++ b/kernel/syscall/proc.c
@@ -125,7 +125,9 @@ int32_t SYSCALL1(sys_proc_run, pid1) {
     goto done;
   }
 
+  spinlock_acquire(&PROCS.spinlock);
   proc->state = PROC_READY;  
+  spinlock_release(&PROCS.spinlock);
 
 done:
   return ret;