Make sure that we're not being tested with MLFQS on.

[pintos-anon] / doc / threads.texi

diff --git a/doc/threads.texi b/doc/threads.texi
index f219db44fd800b94370d6ad2a978aa36f60517b7..e5b087ba349a69f9d5e7f4b02a9fe463033ab878 100644 (file)
--- a/doc/threads.texi
+++ b/doc/threads.texi
@@ -447,9 +447,9 @@ Implement priority scheduling in Pintos.  Priority scheduling is a key
 building block for real-time systems.  Implement functions
 @func{thread_set_priority} to set the priority of the running thread
 and @func{thread_get_priority} to get the running thread's priority.
 building block for real-time systems.  Implement functions
 @func{thread_set_priority} to set the priority of the running thread
 and @func{thread_get_priority} to get the running thread's priority.

-(A thread can examine and modify only its own priority.)  There are
-already prototypes for these functions in @file{threads/thread.h},
-which you should not change.
+(This API only allows a thread to examine and modify its own
+priority.)  There are already prototypes for these functions in
+@file{threads/thread.h}, which you should not change.

 
 Thread priority ranges from @code{PRI_MIN} (0) to @code{PRI_MAX} (59).
 The initial thread priority is passed as an argument to
 
 Thread priority ranges from @code{PRI_MIN} (0) to @code{PRI_MAX} (59).
 The initial thread priority is passed as an argument to


@@ -462,9 +462,8 @@ When a thread is added to the ready list that has a higher priority
 than the currently running thread, the current thread should
 immediately yield the processor to the new thread.  Similarly, when
 threads are waiting for a lock, semaphore or condition variable, the
 than the currently running thread, the current thread should
 immediately yield the processor to the new thread.  Similarly, when
 threads are waiting for a lock, semaphore or condition variable, the

-highest priority waiting thread should be woken up first.  A thread's
-priority may be set at any time, including while the thread is waiting
-on a lock, semaphore, or condition variable.
+highest priority waiting thread should be woken up first.  A thread
+may set its priority at any time.

 
 One issue with priority scheduling is ``priority inversion'': if a
 high priority thread needs to wait for a low priority thread (for
 
 One issue with priority scheduling is ``priority inversion'': if a
 high priority thread needs to wait for a low priority thread (for


@@ -647,6 +646,34 @@ integers? Do I need to check for that?}
 Don't worry about the possibility of timer values overflowing.  Timer
 values are expressed as signed 63-bit numbers, which at 100 ticks per
 second should be good for almost 2,924,712,087 years.
 Don't worry about the possibility of timer values overflowing.  Timer
 values are expressed as signed 63-bit numbers, which at 100 ticks per
 second should be good for almost 2,924,712,087 years.

+
+@item
+@b{The test program mostly works but reports a few out-of-order
+wake ups.  I think it's a problem in the test program.  What gives?}
+
+This test is inherently full of race conditions.  On a real system it
+wouldn't work perfectly all the time either.  However, you can help it
+work more reliably:
+
+@itemize @bullet
+@item
+Make time slices longer by increasing @code{TIME_SLICE} in
+@file{timer.c} to a large value, such as 100.
+
+@item
+Make the timer tick more slowly by decreasing @code{TIMER_FREQ} in
+@file{timer.h} to its minimum value of 19.
+
+@item
+Increase the serial output speed to the maximum of 115,200 bps by
+modifying the call to @func{set_serial} in @func{serial_init_poll} in
+@file{devices/serial.c}.
+@end itemize
+
+The former two changes are only desirable for testing problem 1-1.  You
+should revert them before working on other parts of the project or turn
+in the project.  The latter is harmless, so you can retain it or revert
+it at your option.

 @end enumerate
 
 @node Problem 1-2 Join FAQ
 @end enumerate
 
 @node Problem 1-2 Join FAQ