From: Ben Pfaff <blp@cs.stanford.edu>
Date: Mon, 24 Jul 2006 18:32:38 +0000 (+0000)
Subject: Improvements.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=56f9bd996902d8e8f83688903bf81ccc5dc4bc7e;p=pintos-anon

Improvements.
---

diff --git a/ta-advice/HW2 b/ta-advice/HW2
index 3e9b4ac..7a79395 100644
--- a/ta-advice/HW2
+++ b/ta-advice/HW2
@@ -657,3 +657,30 @@ B11:
     Take off points if an answer assumes that there can be more than
     one thread per process and doesn't mention that this would be an
     extension to the Pintos design.
+
+Check the submitted code, by hand, for the following:
+
+  1. That the system call handler, which is probably in
+     userprog/syscall.c in syscall_handler(), is reasonably
+     abstracted.  It should not all be in one function as one huge
+     switch statement, for example.  The code that accesses user
+     memory should be separated into specialized functions.  If either
+     of these is not the case, or if the code is otherwise difficult
+     to read, take off points.
+
+  2. The "Source Code" section in the Introduction to the Pintos
+     manual says, "Update existing comments as you modify code."  Most
+     students ignore this.  Check whether the comment on
+     process_wait() in process.c has been updated.  At a minimum, the
+     two final sentences ("This function will be implemented in
+     problem 2-2.  For now, it does nothing.") should have been
+     deleted.
+
+  3. Find the implementation of the "open" system call.  Verify that
+     all resources are released in error cases and that errors are
+     properly handled.  One particular problem can be malloc() failure
+     after a file is successfully opened--is the return value checked?
+     If so, is the file closed before returning an error?
+
+     (Failure to check malloc() is in the OVERALL section of the grade
+     report, under DESIGN.)
diff --git a/ta-advice/hw2.txt b/ta-advice/hw2.txt
index f5aab65..f2764a9 100644
--- a/ta-advice/hw2.txt
+++ b/ta-advice/hw2.txt
@@ -101,5 +101,8 @@ PROBLEM 2: SYSTEM CALLS
      -5 Added big array (>= 512 bytes) to struct thread without justifying
     -10 Added big array (>= 1024 bytes) to struct thread
      -5 Superfluous locking on per-thread data structure [which]
+    -10 System call handler is poorly abstracted or unreadable
+     -5 Failed to update comment on process_wait() function after implementing
+     -5 "open" system call fails to release all resources in error cases
 
 Subtotal: /60 (capped at 0)