Use parent pointer instead of ppid.

b1fb19b6 · rsc · 3a057d12 · b1fb19b6 · b1fb19b6
--- a/proc.c
+++ b/proc.c
@@ -118,7 +118,7 @@ copyproc(struct proc *p)
  np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1;

  if(p){  // Copy process state from p.
-    np->ppid = p->pid;
+    np->parent = p;
    memmove(np->tf, p->tf, sizeof(*np->tf));
  
    np->sz = p->sz;
@@ -366,15 +366,13 @@ proc_exit(void)

  acquire(&proc_table_lock);

-  // Wake up waiting parent.
-  for(p = proc; p < &proc[NPROC]; p++)
-    if(p->pid == cp->ppid)
-      wakeup1(p);
+  // Parent might be sleeping in proc_wait.
+  wakeup1(cp->parent);

  // Pass abandoned children to init.
  for(p = proc; p < &proc[NPROC]; p++){
-    if(p->ppid == cp->pid){
-      p->ppid = initproc->pid;
+    if(p->parent == cp){
+      p->parent = initproc;
      if(p->state == ZOMBIE)
        wakeup1(initproc);
    }
@@ -403,7 +401,7 @@ proc_wait(void)
      p = &proc[i];
      if(p->state == UNUSED)
        continue;
-      if(p->ppid == cp->pid){
+      if(p->parent == cp){
        if(p->state == ZOMBIE){
          // Found one.
          kfree(p->mem, p->sz);
@@ -411,7 +409,7 @@ proc_wait(void)
          pid = p->pid;
          p->state = UNUSED;
          p->pid = 0;
-          p->ppid = 0;
+          p->parent = 0;
          p->name[0] = 0;
          release(&proc_table_lock);
          return pid;

--- a/proc.h
+++ b/proc.h
@@ -33,7 +33,7 @@ struct proc {
  char *kstack;             // Bottom of kernel stack for this process
  enum proc_state state;    // Process state
  int pid;                  // Process ID
-  int ppid;                 // Parent pid
+  struct proc *parent;      // Parent process
  void *chan;               // If non-zero, sleeping on chan
  int killed;               // If non-zero, have been killed
  struct file *ofile[NOFILE];  // Open files