From: Ben Pfaff <blp@cs.stanford.edu>
Date: Thu, 18 May 2006 19:37:03 +0000 (+0000)
Subject: Test interaction between priority donation and thread_set_priority().
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commitdiff_plain;h=c75a1a1b7c79c1a516256b8cf072631a7aa575eb

Test interaction between priority donation and thread_set_priority().
Suggestion from Godmar Back.
---

diff --git a/doc/threads.texi b/doc/threads.texi
index f5e6058..eeb17ee 100644
--- a/doc/threads.texi
+++ b/doc/threads.texi
@@ -714,9 +714,11 @@ preempting whatever thread is currently running.
 
 @item How does @func{thread_set_priority} affect a thread receiving donations?
 
-It should do something sensible, but no particular behavior is
-required.  None of the test cases call @func{thread_set_priority} from a
-thread while it is receiving a priority donation.
+It sets the thread's base priority.  The thread's effective priority
+becomes the higher of the newly set priority or the highest donated
+priority.  When the donations are released, the thread's priority
+becomes the one set through the function call.  This behavior is checked
+by the @code{priority-donate-lower} test.
 
 @item Calling @func{printf} in @func{sema_up} or @func{sema_down} reboots!
 
diff --git a/src/tests/threads/Make.tests b/src/tests/threads/Make.tests
index 3b6bfd7..f1e239e 100644
--- a/src/tests/threads/Make.tests
+++ b/src/tests/threads/Make.tests
@@ -5,10 +5,10 @@ tests/threads_TESTS = $(addprefix tests/threads/,alarm-single		\
 alarm-multiple alarm-simultaneous alarm-priority alarm-zero		\
 alarm-negative priority-change priority-donate-one			\
 priority-donate-multiple priority-donate-multiple2			\
-priority-donate-nest priority-donate-sema priority-fifo			\
-priority-preempt priority-sema priority-condvar mlfqs-load-1		\
-mlfqs-load-60 mlfqs-load-avg mlfqs-recent-1 mlfqs-fair-2 mlfqs-fair-20	\
-mlfqs-nice-2 mlfqs-nice-10 mlfqs-block)
+priority-donate-nest priority-donate-sema priority-donate-lower		\
+priority-fifo priority-preempt priority-sema priority-condvar		\
+mlfqs-load-1 mlfqs-load-60 mlfqs-load-avg mlfqs-recent-1 mlfqs-fair-2	\
+mlfqs-fair-20 mlfqs-nice-2 mlfqs-nice-10 mlfqs-block)
 
 # Sources for tests.
 tests/threads_SRC  = tests/threads/tests.c
@@ -23,6 +23,7 @@ tests/threads_SRC += tests/threads/priority-donate-multiple.c
 tests/threads_SRC += tests/threads/priority-donate-multiple2.c
 tests/threads_SRC += tests/threads/priority-donate-nest.c
 tests/threads_SRC += tests/threads/priority-donate-sema.c
+tests/threads_SRC += tests/threads/priority-donate-lower.c
 tests/threads_SRC += tests/threads/priority-fifo.c
 tests/threads_SRC += tests/threads/priority-preempt.c
 tests/threads_SRC += tests/threads/priority-sema.c
diff --git a/src/tests/threads/priority-donate-lower.c b/src/tests/threads/priority-donate-lower.c
new file mode 100644
index 0000000..3f63db8
--- /dev/null
+++ b/src/tests/threads/priority-donate-lower.c
@@ -0,0 +1,51 @@
+/* The main thread acquires a lock.  Then it creates a
+   higher-priority thread that blocks acquiring the lock, causing
+   it to donate their priorities to the main thread.  The main
+   thread attempts to lower its priority, which should not take
+   effect until the donation is released. */
+
+#include <stdio.h>
+#include "tests/threads/tests.h"
+#include "threads/init.h"
+#include "threads/synch.h"
+#include "threads/thread.h"
+
+static thread_func acquire_thread_func;
+
+void
+test_priority_donate_lower (void) 
+{
+  struct lock lock;
+
+  /* This test does not work with the MLFQS. */
+  ASSERT (!enable_mlfqs);
+
+  /* Make sure our priority is the default. */
+  ASSERT (thread_get_priority () == PRI_DEFAULT);
+
+  lock_init (&lock);
+  lock_acquire (&lock);
+  thread_create ("acquire", PRI_DEFAULT + 10, acquire_thread_func, &lock);
+  msg ("Main thread should have priority %d.  Actual priority: %d.",
+       PRI_DEFAULT + 10, thread_get_priority ());
+
+  msg ("Lowering base priority...");
+  thread_set_priority (PRI_DEFAULT - 10);
+  msg ("Main thread should have priority %d.  Actual priority: %d.",
+       PRI_DEFAULT + 10, thread_get_priority ());
+  lock_release (&lock);
+  msg ("acquire must already have finished.");
+  msg ("Main thread should have priority %d.  Actual priority: %d.",
+       PRI_DEFAULT - 10, thread_get_priority ());
+}
+
+static void
+acquire_thread_func (void *lock_) 
+{
+  struct lock *lock = lock_;
+
+  lock_acquire (lock);
+  msg ("acquire: got the lock");
+  lock_release (lock);
+  msg ("acquire: done");
+}
diff --git a/src/tests/threads/priority-donate-lower.ck b/src/tests/threads/priority-donate-lower.ck
new file mode 100644
index 0000000..b009fd8
--- /dev/null
+++ b/src/tests/threads/priority-donate-lower.ck
@@ -0,0 +1,15 @@
+# -*- perl -*-
+use strict;
+use warnings;
+use tests::tests;
+check_expected ([<<'EOF']);
+(priority-donate-lower) begin
+(priority-donate-lower) Main thread should have priority 41.  Actual priority: 41.
+(priority-donate-lower) Lowering base priority...
+(priority-donate-lower) Main thread should have priority 41.  Actual priority: 41.
+(priority-donate-lower) acquire: got the lock
+(priority-donate-lower) acquire: done
+(priority-donate-lower) acquire must already have finished.
+(priority-donate-lower) Main thread should have priority 21.  Actual priority: 21.
+(priority-donate-lower) end
+EOF
diff --git a/src/tests/threads/tests.c b/src/tests/threads/tests.c
index b515372..3f0327f 100644
--- a/src/tests/threads/tests.c
+++ b/src/tests/threads/tests.c
@@ -23,6 +23,7 @@ static const struct test tests[] =
     {"priority-donate-multiple2", test_priority_donate_multiple2},
     {"priority-donate-nest", test_priority_donate_nest},
     {"priority-donate-sema", test_priority_donate_sema},
+    {"priority-donate-lower", test_priority_donate_lower},
     {"priority-fifo", test_priority_fifo},
     {"priority-preempt", test_priority_preempt},
     {"priority-sema", test_priority_sema},
diff --git a/src/tests/threads/tests.h b/src/tests/threads/tests.h
index 1fe839e..81e9663 100644
--- a/src/tests/threads/tests.h
+++ b/src/tests/threads/tests.h
@@ -17,6 +17,7 @@ extern test_func test_priority_donate_multiple;
 extern test_func test_priority_donate_multiple2;
 extern test_func test_priority_donate_sema;
 extern test_func test_priority_donate_nest;
+extern test_func test_priority_donate_lower;
 extern test_func test_priority_fifo;
 extern test_func test_priority_preempt;
 extern test_func test_priority_sema;