From 147855e5219e91886e71e796fd51fbc6b1a056d2 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Thu, 22 Oct 2020 06:36:36 -0400
Subject: [PATCH] test for closed pipe or killed on every char, not just if
 pipe full

---
 kernel/pipe.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/kernel/pipe.c b/kernel/pipe.c
index 7ed402d..b6eefb9 100644
--- a/kernel/pipe.c
+++ b/kernel/pipe.c
@@ -76,26 +76,29 @@ pipeclose(struct pipe *pi, int writable)
 int
 pipewrite(struct pipe *pi, uint64 addr, int n)
 {
-  int i;
-  char ch;
+  int i = 0;
   struct proc *pr = myproc();
 
   acquire(&pi->lock);
-  for(i = 0; i < n; i++){
-    while(pi->nwrite == pi->nread + PIPESIZE){  //DOC: pipewrite-full
-      if(pi->readopen == 0 || pr->killed){
-        release(&pi->lock);
-        return -1;
-      }
+  while(i < n){
+    if(pi->readopen == 0 || pr->killed){
+      release(&pi->lock);
+      return -1;
+    }
+    if(pi->nwrite == pi->nread + PIPESIZE){ //DOC: pipewrite-full
       wakeup(&pi->nread);
       sleep(&pi->nwrite, &pi->lock);
+    } else {
+      char ch;
+      if(copyin(pr->pagetable, &ch, addr + i, 1) == -1)
+        break;
+      pi->data[pi->nwrite++ % PIPESIZE] = ch;
+      i++;
     }
-    if(copyin(pr->pagetable, &ch, addr + i, 1) == -1)
-      break;
-    pi->data[pi->nwrite++ % PIPESIZE] = ch;
   }
   wakeup(&pi->nread);
   release(&pi->lock);
+
   return i;
 }