added some thoughts on TODO items

diff --git a/TODO b/TODO
index 9d3d6c23509adc26cbb2b97ceb88e5e4c873e6de..017db82200fa63932869c6b92a4ddfc323714196 100644 (file)
--- a/TODO
+++ b/TODO
@@ -1,5 +1,34 @@
 -*- text -*-
 
+Godmar says:
+
+- In Project 2, we're missing tests that pass arguments to system calls
+that span multiple pages, where some are mapped and some are not. 
+An implementation that only checks the first page, rather than all pages 
+that can be touched during a call to read()/write() passes all tests.
+
+- In Project 2, we're missing a test that would fail if they assumed
+that contiguous user-virtual addresses are laid out contiguously 
+in memory.  The loading code should ensure that non-contiguous 
+physical pages are allocated for the data segment (at least.)
+
+- Need some tests that test that illegal accesses lead to process
+termination. I have written some, will add them. In P2, obviously, 
+this would require that the students break this functionality since 
+the page directory is initialized for them, still it would be good 
+to have.
+
+- There does not appear to be a test that checks that they close all
+fd's on exit.  Idea: add statistics & self-diagnostics code to palloc.c
+and malloc.c.  Self-diagnostics code could be used for debugging.
+The statistics code would report how much kernel memory is free.
+Add a system call "get_kernel_memory_information".  User programs
+could engage in a variety of activities and notice leaks by checking
+the kernel memory statistics.
+
+---
+
+
 From: "Godmar Back" <godmar@gmail.com>
 Subject: priority donation tests
 To: "Ben Pfaff" <blp@cs.stanford.edu>
@@ -68,6 +97,12 @@ immediately, forcing the scheduler to switch to the other
 equal-priority thread. Both wake-up times must be the same (and match
 the planned wake-up time.)
 
+PS:
+I actually tested it and it's hard to pass with the current ips setting.
+The bounds on how quickly a thread would need to be able to return after
+sleep appear too tight.  Need another idea.
+
+---
 From: "Waqar Mohsin" <wmohsin@gmail.com>
 Subject: 3 questions about switch_threads() in switch.S
 To: blp@cs.stanford.edu, joshwise@stanford.edu
@@ -286,6 +321,11 @@ via Godmar Back:
 
 * lock_acquire(), lock_release() don't need additional intr_dis/enable
   calls, because the semaphore protects lock->holder.
+  [ Think this over: is this really true when priority donation is 
+    implemented?  intr_dis/enable prevents the race with thread_set_priority. 
+    Leaving it there could help the students getting the correct synchronization
+    right.
+  ]