Update Intel architecture guide references to latest.

[pintos-anon] / doc / threads.texi

diff --git a/doc/threads.texi b/doc/threads.texi
index 6b93dbb0badbdd7cab26cb02e6ecee2826248167..8f07bb792ff461e512c770818efc7bfb11550a17 100644 (file)
--- a/doc/threads.texi
+++ b/doc/threads.texi
@@ -185,8 +185,8 @@ project 3.  For now, you can ignore it.
 
 @item flags.h
 Macros that define a few bits in the 80@var{x}86 ``flags'' register.
 
 @item flags.h
 Macros that define a few bits in the 80@var{x}86 ``flags'' register.

-Probably of no interest.  See @bibref{IA32-v1}, section 3.4.3, for more
-information.
+Probably of no interest.  See @bibref{IA32-v1}, section 3.4.3, ``EFLAGS
+Register,'' for more information.

 @end table
 
 @menu
 @end table
 
 @menu


@@ -464,7 +464,8 @@ multiple donations, in which multiple priorities are donated to a single
 thread.  You must also handle nested donation: if @var{H} is waiting on
 a lock that @var{M} holds and @var{M} is waiting on a lock that @var{L}
 holds, then both @var{M} and @var{L} should be boosted to @var{H}'s
 thread.  You must also handle nested donation: if @var{H} is waiting on
 a lock that @var{M} holds and @var{M} is waiting on a lock that @var{L}
 holds, then both @var{M} and @var{L} should be boosted to @var{H}'s

-priority.
+priority.  If necessary, you may impose a reasonable limit on depth of
+nested priority donation, such as 8 levels.

 
 You must implement priority donation for locks.  You need not
 implement priority donation for semaphores or condition variables
 
 You must implement priority donation for locks.  You need not
 implement priority donation for semaphores or condition variables


@@ -496,14 +497,15 @@ The priority scheduler is not used in any later project.
 Implement a multilevel feedback queue scheduler similar to the
 4.4@acronym{BSD} scheduler to
 reduce the average response time for running jobs on your system.
 Implement a multilevel feedback queue scheduler similar to the
 4.4@acronym{BSD} scheduler to
 reduce the average response time for running jobs on your system.

-@xref{4.4BSD Scheduler}, for a detailed description of
-the MLFQS requirements.
+@xref{4.4BSD Scheduler}, for detailed requirements.

 
 

-The advanced scheduler builds on the priority scheduler.  You should
-have the priority scheduler working, except possibly for priority
-donation, before you start work on the advanced scheduler.
+Like the priority scheduler, the advanced scheduler chooses the thread
+to run based on priorities.  However, the advanced scheduler does not do
+priority donation.  Thus, we recommend that you have the priority
+scheduler working, except possibly for priority donation, before you
+start work on the advanced scheduler.

 
 

-You must write your code so that we can choose a scheduling algorithm
+You must write your code to allow us to choose a scheduling algorithm

 policy at Pintos startup time.  By default, the priority scheduler
 must be active, but we must be able to choose the 4.4@acronym{BSD}
 scheduler
 policy at Pintos startup time.  By default, the priority scheduler
 must be active, but we must be able to choose the 4.4@acronym{BSD}
 scheduler


@@ -517,8 +519,6 @@ directly control their own priorities.  The @var{priority} argument to
 @func{thread_set_priority}, and @func{thread_get_priority} should return
 the thread's current priority as set by the scheduler.
 
 @func{thread_set_priority}, and @func{thread_get_priority} should return
 the thread's current priority as set by the scheduler.
 

-The 4.4@acronym{BSD} scheduler does not implement priority donation.
-

 The advanced scheduler is not used in any later project.
 
 @node Project 1 FAQ
 The advanced scheduler is not used in any later project.
 
 @node Project 1 FAQ


@@ -531,6 +531,12 @@ Here's a summary of our reference solution, produced by the
 @command{diffstat} program.  The final row gives total lines inserted
 and deleted; a changed line counts as both an insertion and a deletion.
 
 @command{diffstat} program.  The final row gives total lines inserted
 and deleted; a changed line counts as both an insertion and a deletion.
 

+The reference solution represents just one possible solution.  Many
+other solutions are also possible and many of those differ greatly from
+the reference solution.  Some excellent solutions may not modify all the
+files modified by the reference solution, and some may modify files not
+modified by the reference solution.
+

 @verbatim
  devices/timer.c       |   42 +++++-
  threads/fixed-point.h |  120 ++++++++++++++++++
 @verbatim
  devices/timer.c       |   42 +++++-
  threads/fixed-point.h |  120 ++++++++++++++++++


@@ -585,8 +591,40 @@ to cause many of the tests to fail.
 There are @code{TIME_SLICE} ticks per time slice.  This macro is
 declared in @file{threads/thread.c}.  The default is 4 ticks.
 
 There are @code{TIME_SLICE} ticks per time slice.  This macro is
 declared in @file{threads/thread.c}.  The default is 4 ticks.
 

-We don't recommend changing this values, because any changes are likely
+We don't recommend changing this value, because any changes are likely

 to cause many of the tests to fail.
 to cause many of the tests to fail.

+
+@item How do I run the tests?
+
+@xref{Testing}.
+
+@item Why do I get a test failure in @func{pass}?
+
+@anchor{The pass function fails}
+You are probably looking at a backtrace that looks something like this:
+
+@example
+0xc0108810: debug_panic (../../lib/kernel/debug.c:32)
+0xc010a99f: pass (../../tests/threads/tests.c:93)
+0xc010bdd3: test_mlfqs_load_1 (../../tests/threads/mlfqs-load-1.c:33)
+0xc010a8cf: run_test (../../tests/threads/tests.c:51)
+0xc0100452: run_task (../../threads/init.c:283)
+0xc0100536: run_actions (../../threads/init.c:333)
+0xc01000bb: main (../../threads/init.c:137)
+@end example
+
+This is just confusing output from the @command{backtrace} program.  It
+does not actually mean that @func{pass} called @func{debug_panic}.  In
+fact, @func{fail} called @func{debug_panic} (via the @func{PANIC}
+macro).  GCC knows that @func{debug_panic} does not return, because it
+is declared @code{NO_RETURN} (@pxref{Function and Parameter
+Attributes}), so it doesn't include any code in @func{pass} to take
+control when @func{debug_panic} returns.  This means that the return
+address on the stack looks like it is at the beginning of the function
+that happens to follow @func{fail} in memory, which in this case happens
+to be @func{pass}.
+
+@xref{Backtraces}, for more information.

 @end table
 
 @menu
 @end table
 
 @menu


@@ -643,8 +681,8 @@ If multiple threads have the same highest priority,
 
 Priority donation only changes the priority of the donee
 thread.  The donor thread's priority is unchanged.  
 
 Priority donation only changes the priority of the donee
 thread.  The donor thread's priority is unchanged.  

-Priority donation is not additive: if thread @var{A} (with priority 5) donates
-to thread @var{B} (with priority 3), then @var{B}'s new priority is 5, not 8.
+Priority donation is not additive: if thread @var{A} (with priority 3) donates
+to thread @var{B} (with priority 5), then @var{B}'s new priority is 3, not 8.

 
 @item Can a thread's priority change while it is on the ready queue?
 
 
 @item Can a thread's priority change while it is on the ready queue?
 


@@ -685,4 +723,12 @@ just before the first @func{printf} in @func{main}.  Then modify
 
 It doesn't have to.  We won't test priority donation and the advanced
 scheduler at the same time.
 
 It doesn't have to.  We won't test priority donation and the advanced
 scheduler at the same time.

+
+@item Can I use one queue instead of 64 queues?
+
+Yes, that's fine.  It's easiest to describe the algorithm in terms of 64
+separate queues, but that doesn't mean you have to implement it that
+way.
+
+If you use a single queue, it should probably be sorted.

 @end table
 @end table