Hold proc->lock while killing the process

kernel/proc/proc.c

@@ -24,12 +24,6 @@
 #include <amd64/intr_defs.h>
 #endif
 
-/*
- * Lock ordering:
- * 1. proc_tree_lock
- * 2. [cpu]->lock
- */
-
 static struct rb_node_link* proc_tree = NULL;
 static spin_lock_t proc_tree_lock = SPIN_LOCK_INIT;
 
@@ -266,7 +260,9 @@ void proc_kill (struct proc* proc) {
   atomic_store (&proc->state, PROC_DEAD);
 
   spin_lock (&proc_tree_lock);
+  spin_lock (&proc->lock);
   rbtree_delete (&proc_tree, &proc->proc_tree_link);
+  spin_unlock (&proc->lock);
   spin_unlock (&proc_tree_lock);
 
   struct cpu* cpu = proc->cpu;