1 files changed, 16 insertions, 24 deletions

diff --git a/kernel/proc.c b/kernel/proc.c
index 087d504..b9babed 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -55,7 +55,7 @@ mycpu(void) {
   return c;
 }
 
-// Return the current struct proc *.
+// Return the current struct proc *, or zero if none.
 struct proc*
 myproc(void) {
   push_off();
@@ -314,13 +314,12 @@ void
 exit(void)
 {
   struct proc *p = myproc();
-  int fd;
 
   if(p == initproc)
     panic("init exiting");
 
   // Close all open files.
-  for(fd = 0; fd < NOFILE; fd++){
+  for(int fd = 0; fd < NOFILE; fd++){
     if(p->ofile[fd]){
       struct file *f = p->ofile[fd];
       fileclose(f);
@@ -337,14 +336,14 @@ exit(void)
     
   acquire(&p->lock);
 
-  // Give our children to init.
+  // Give any children to init.
   reparent(p, p->parent);
 
-  p->state = ZOMBIE;
-
   // Parent might be sleeping in wait().
   wakeup1(p->parent);
 
+  p->state = ZOMBIE;
+
   release(&p->parent->lock);
 
   // Jump into the scheduler, never to return.
@@ -416,7 +415,7 @@ scheduler(void)
   
   c->proc = 0;
   for(;;){
-    // Give devices a brief chance to interrupt.
+    // Avoid deadlock by ensuring that devices can interrupt.
     intr_on();
 
     for(p = proc; p < &proc[NPROC]; p++) {
@@ -505,12 +504,6 @@ sleep(void *chan, struct spinlock *lk)
 {
   struct proc *p = myproc();
   
-  if(p == 0)
-    panic("sleep");
-
-  if(lk == 0)
-    panic("sleep without lk");
-
   // Must acquire p->lock in order to
   // change p->state and then call sched.
   // Once we hold p->lock, we can be
@@ -538,17 +531,6 @@ sleep(void *chan, struct spinlock *lk)
   }
 }
 
-//PAGEBREAK!
-// Wake up p if it is sleeping in wait(); used by exit().
-// Caller must hold p->lock.
-static void
-wakeup1(struct proc *p)
-{
-  if(p->chan == p && p->state == SLEEPING) {
-    p->state = RUNNABLE;
-  }
-}
-
 // Wake up all processes sleeping on chan.
 // Must be called without any p->lock.
 void
@@ -565,6 +547,16 @@ wakeup(void *chan)
   }
 }
 
+// Wake up p if it is sleeping in wait(); used by exit().
+// Caller must hold p->lock.
+static void
+wakeup1(struct proc *p)
+{
+  if(p->chan == p && p->state == SLEEPING) {
+    p->state = RUNNABLE;
+  }
+}
+
 // Kill the process with the given pid.
 // The victim won't exit until it tries to return
 // to user space (see usertrap() in trap.c).