114 lines
3.4 KiB
C
Executable file
114 lines
3.4 KiB
C
Executable file
/* The main thread set its priority to PRI_MIN and creates 7 threads
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(thread 1..7) with priorities PRI_MIN + 3, 6, 9, 12, ...
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The main thread initializes 8 locks: lock 0..7 and acquires lock 0.
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When thread[i] starts, it first acquires lock[i] (unless i == 7.)
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Subsequently, thread[i] attempts to acquire lock[i-1], which is held by
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thread[i-1], except for lock[0], which is held by the main thread.
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Because the lock is held, thread[i] donates its priority to thread[i-1],
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which donates to thread[i-2], and so on until the main thread
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receives the donation.
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After threads[1..7] have been created and are blocked on locks[0..7],
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the main thread releases lock[0], unblocking thread[1], and being
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preempted by it.
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Thread[1] then completes acquiring lock[0], then releases lock[0],
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then releases lock[1], unblocking thread[2], etc.
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Thread[7] finally acquires & releases lock[7] and exits, allowing
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thread[6], then thread[5] etc. to run and exit until finally the
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main thread exits.
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In addition, interloper threads are created at priority levels
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p = PRI_MIN + 2, 5, 8, 11, ... which should not be run until the
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corresponding thread with priority p + 1 has finished.
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Written by Godmar Back <gback@cs.vt.edu> */
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#include <stdio.h>
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#include "tests/threads/tests.h"
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#include "threads/init.h"
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#include "threads/synch.h"
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#include "threads/thread.h"
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#define NESTING_DEPTH 8
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struct lock_pair
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{
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struct lock *second;
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struct lock *first;
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};
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static thread_func donor_thread_func;
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static thread_func interloper_thread_func;
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void
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test_priority_donate_chain (void)
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{
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int i;
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struct lock locks[NESTING_DEPTH - 1];
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struct lock_pair lock_pairs[NESTING_DEPTH];
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/* This test does not work with the MLFQS. */
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ASSERT (!thread_mlfqs);
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thread_set_priority (PRI_MIN);
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for (i = 0; i < NESTING_DEPTH - 1; i++)
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lock_init (&locks[i]);
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lock_acquire (&locks[0]);
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msg ("%s got lock.", thread_name ());
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for (i = 1; i < NESTING_DEPTH; i++)
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{
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char name[16];
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int thread_priority;
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snprintf (name, sizeof name, "thread %d", i);
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thread_priority = PRI_MIN + i * 3;
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lock_pairs[i].first = i < NESTING_DEPTH - 1 ? locks + i: NULL;
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lock_pairs[i].second = locks + i - 1;
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thread_create (name, thread_priority, donor_thread_func, lock_pairs + i);
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msg ("%s should have priority %d. Actual priority: %d.",
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thread_name (), thread_priority, thread_get_priority ());
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snprintf (name, sizeof name, "interloper %d", i);
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thread_create (name, thread_priority - 1, interloper_thread_func, NULL);
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}
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lock_release (&locks[0]);
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msg ("%s finishing with priority %d.", thread_name (),
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thread_get_priority ());
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}
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static void
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donor_thread_func (void *locks_)
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{
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struct lock_pair *locks = locks_;
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if (locks->first)
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lock_acquire (locks->first);
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lock_acquire (locks->second);
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msg ("%s got lock", thread_name ());
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lock_release (locks->second);
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msg ("%s should have priority %d. Actual priority: %d",
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thread_name (), (NESTING_DEPTH - 1) * 3,
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thread_get_priority ());
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if (locks->first)
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lock_release (locks->first);
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msg ("%s finishing with priority %d.", thread_name (),
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thread_get_priority ());
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}
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static void
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interloper_thread_func (void *arg_ UNUSED)
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{
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msg ("%s finished.", thread_name ());
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}
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// vim: sw=2
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