swtch saves callee-saved registers

swtch idles on per-CPU stack, not on calling process's stack
fix pipe bugs
usertest.c tests pipes, fork, exit, close

1 files changed, 17 insertions, 13 deletions

diff --git a/fd.c b/fd.c
index 0546cef..8b59605 100644
--- a/fd.c
+++ b/fd.c
@@ -37,19 +37,6 @@ fd_alloc()
   return 0;
 }
 
-void
-fd_close(struct fd *fd)
-{
-  if(fd->type == FD_CLOSED || fd->count <= 0)
-    panic("fd_close");
-  fd->count -= 1;
-  if(fd->count == 0){
-    if(fd->type == FD_PIPE)
-      pipe_close(fd->pipe, fd->writeable);
-    fd->type = FD_CLOSED;
-  }
-}
-
 /*
  * addr is a kernel address, pointing into some process's p->mem.
  */
@@ -78,3 +65,20 @@ fd_read(struct fd *fd, char *addr, int n)
     return -1;
   }
 }
+
+void
+fd_close(struct fd *fd)
+{
+  if(fd->count < 1 || fd->type == FD_CLOSED)
+    panic("fd_close");
+  fd->count -= 1;
+
+  if(fd->count == 0){
+    if(fd->type == FD_PIPE){
+      pipe_close(fd->pipe, fd->writeable);
+    } else {
+      panic("fd_close");
+    }
+    fd->type = FD_CLOSED;
+  }
+}