/* The main thread acquires locks A and B, then it creates three
higher-priority threads. The first two of these threads block
acquiring one of the locks and thus donate their priority to
the main thread. The main thread releases the locks in turn
and relinquishes its donated priorities, allowing the third thread
to run.
In this test, the main thread releases the locks in a different
order compared to priority-donate-multiple.c.
Written by Godmar Back
Based on a test originally submitted for Stanford’s CS 140 in
winter 1999 by Matt Franklin
Greg Hutchins
#include
#include “tests/threads/tests.h”
#include “threads/init.h”
#include “threads/lock.h”
#include “threads/thread.h”
static thread_func a_thread_func;
static thread_func b_thread_func;
static thread_func c_thread_func;
void
test_priority_donate_multiple2 (void)
{
struct lock a, b;
/* This test does not work with the MLFQS. */
ASSERT (!thread_mlfqs);
/* Make sure our priority is the default. */
ASSERT (thread_get_priority () == PRI_DEFAULT);
lock_init (&a);
lock_init (&b);
lock_acquire (&a);
lock_acquire (&b);
thread_create (“a”, PRI_DEFAULT + 3, a_thread_func, &a);
msg (“Main thread should have priority %d. Actual priority: %d.”,
PRI_DEFAULT + 3, thread_get_priority ());
thread_create (“c”, PRI_DEFAULT + 1, c_thread_func, NULL);
thread_create (“b”, PRI_DEFAULT + 5, b_thread_func, &b);
msg (“Main thread should have priority %d. Actual priority: %d.”,
PRI_DEFAULT + 5, thread_get_priority ());
lock_release (&a);
msg (“Main thread should have priority %d. Actual priority: %d.”,
PRI_DEFAULT + 5, thread_get_priority ());
lock_release (&b);
msg (“Threads b, a, c should have just finished, in that order.”);
msg (“Main thread should have priority %d. Actual priority: %d.”,
PRI_DEFAULT, thread_get_priority ());
}
static void
a_thread_func (void *lock_)
{
struct lock *lock = lock_;
lock_acquire (lock);
msg (“Thread a acquired lock a.”);
lock_release (lock);
msg (“Thread a finished.”);
}
static void
b_thread_func (void *lock_)
{
struct lock *lock = lock_;
lock_acquire (lock);
msg (“Thread b acquired lock b.”);
lock_release (lock);
msg (“Thread b finished.”);
}
static void
c_thread_func (void *a_ UNUSED)
{
msg (“Thread c finished.”);
}