Allow .png as alternate for ASCII art.

[pintos-anon] / doc / threads.texi

diff --git a/doc/threads.texi b/doc/threads.texi
index 314ee61ca865aef58c4cb51cc4260eea8a965001..40565994f536bbbec06e7a9beb25ae494cd4a60a 100644 (file)
--- a/doc/threads.texi
+++ b/doc/threads.texi
@@ -591,6 +591,34 @@ to cause many of the tests to fail.
 @item How do I run the tests?
 
 @xref{Testing}.
 @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


@@ -689,4 +717,12 @@ 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