-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>
-Date: Fri, 3 Mar 2006 11:02:08 -0500
-
-Ben,
-
-it seems the priority donation tests are somewhat incomplete and allow
-incorrect implementations to pass with a perfect score.
-
-We are seeing the following wrong implementations pass all tests:
-
-- Implementations that assume locks are released in the opposite order
-in which they're acquired. The students implement this by
-popping/pushing on the donation list.
-
-- Implementations that assume that the priority of a thread waiting on
-a semaphore or condition variable cannot change between when the
-thread was blocked and when it is unblocked. The students implement
-this by doing an insert into an ordered list on block, rather than
-picking the maximum thread on unblock.
-
-Neither of these two cases is detected; do you currently check for
-these mistakes manually?
-
-I wrote a test that checks for the first case; it is here:
-http://people.cs.vt.edu/~gback/pintos/priority-donate-multiple-2.patch
-
-[...]
-
-I also wrote a test case for the second scenario:
-http://people.cs.vt.edu/~gback/pintos/priority-donate-sema.c
-http://people.cs.vt.edu/~gback/pintos/priority-donate-sema.ck
-
-I put the other tests up here:
-http://people.cs.vt.edu/~gback/pintos/priority-donate-multiple2.c
-http://people.cs.vt.edu/~gback/pintos/priority-donate-multiple2.ck
-
-From: "Godmar Back" <godmar@gmail.com>
-Subject: multiple threads waking up at same clock tick
-To: "Ben Pfaff" <blp@cs.stanford.edu>
-Date: Wed, 1 Mar 2006 08:14:47 -0500
-
-Greg Benson points out another potential TODO item for P1.
-
-----
-One thing I recall:
-
-The alarm tests do not test to see if multiple threads are woken up if
-their timers have expired. That is, students can write a solution
-that just wakes up the first thread on the sleep queue rather than
-check for additional threads. Of course, the next thread will be
-woken up on the next tick. Also, this might be hard to test.
-
----
-Way to test this: (from Godmar Back)
-
-Thread A with high priority spins until 'ticks' changes, then calls to
-timer_sleep(X), Thread B with lower priority is then resumed, calls
-set_priority to make its priority equal to that of thread A, then
-calls timer_sleep(X), all of that before the next clock interrupt
-arrives.
-
-On wakeup, each thread records wake-up time and calls yield
-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: "Godmar Back" <godmar@gmail.com>
-
-For reasons I don't currently understand, some of our students seem
-hesitant to include each thread in a second "all-threads" list and are
-looking for ways to implement the advanced scheduler without one.
-
-Currently, I believe, all tests for the mlfqs are such that all
-threads are either ready or sleeping in timer_sleep(). This allows for
-an incorrect implementation in which recent-cpu and priorities are
-updated only for those threads that are on the alarm list or the ready
-list.
-
-The todo item would be a test where a thread is blocked on a
-semaphore, lock or condition variable and have its recent_cpu decay to
-zero, and check that it's scheduled right after the unlock/up/signal.
-
-From: "Godmar Back" <godmar@gmail.com>
-Subject: set_priority & donation - a TODO item
-To: "Ben Pfaff" <blp@cs.stanford.edu>
-Date: Mon, 20 Feb 2006 22:20:26 -0500
-
-Ben,
-
-it seems that there are currently no tests that check the proper
-behavior of thread_set_priority() when called by a thread that is
-running under priority donation. The proper behavior, I assume, is to
-temporarily drop the donation if the set priority is higher, and to
-reassume the donation should the thread subsequently set its own
-priority again to a level that's lower than a still active donation.
-
- - Godmar