Explain that multiple file descriptors for a single file are

[pintos-anon] / doc / userprog.texi

diff --git a/doc/userprog.texi b/doc/userprog.texi
index bb05dfb326b091e48cdeff21f744c73ddd0179f6..f005d55e41add3d1cd3c7fd506deb4c23b7d5005 100644 (file)
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -314,11 +314,6 @@ the running process.  However, even in the kernel, an attempt to
 access memory at an unmapped user virtual address
 will cause a page fault.
 
 access memory at an unmapped user virtual address
 will cause a page fault.
 

-You must handle memory fragmentation gracefully, that is, a process that
-needs @var{N} pages of user virtual memory must not require those pages
-to be contiguous in physical memory (or, equivalently, in kernel virtual
-memory).
-

 @menu
 * Typical Memory Layout::       
 @end menu
 @menu
 * Typical Memory Layout::       
 @end menu


@@ -679,6 +674,12 @@ as explicitly described below.
 
 Each process has an independent set of file descriptors.  File
 descriptors are not inherited by child processes.
 
 Each process has an independent set of file descriptors.  File
 descriptors are not inherited by child processes.

+
+When a single file is opened more than once, whether by a single
+process or different processes, each @code{open} returns a new file
+descriptor.  Different file descriptors for a single file are closed
+independently in separate calls to @code{close} and they do not share
+a file position.

 @end deftypefn
 
 @deftypefn {System Call} int filesize (int @var{fd})
 @end deftypefn
 
 @deftypefn {System Call} int filesize (int @var{fd})