Revamp the mthread library and update test59

Before, the 'main thread' of a process was never taken into account anywhere in
the library, causing mutexes not to work properly (and consequently, neither
did the condition variables). For example, if the 'main thread' (that is, the
thread which is started at the beginning of a process; not a spawned thread by
the library) would lock a mutex, it wasn't actually locked.

lib/libmthread/queue.c

@@ -1,5 +1,6 @@
 #include <minix/mthread.h>
 #include "global.h"
+#include "proto.h"
 
 /*===========================================================================*
  *				mthread_queue_add			     *
@@ -12,12 +13,18 @@ mthread_thread_t thread;
  * only one queue at the same time, we can use the threads array's 'next'
  * pointer to point to the next thread on the queue.
  */
+  mthread_tcb_t *last;
+
+  if (!isokthreadid(thread))
+  	mthread_panic("Can't append invalid thread ID to a queue");
+
+  last = mthread_find_tcb(thread);
 
   if (mthread_queue_isempty(queue)) {
-	queue->head = queue->tail = thread;
-  } else {
-	threads[queue->tail].m_next = thread;
-	queue->tail = thread; /* 'thread' is the new last in line */
+  	queue->head = queue->tail = last;
+  } else  {
+	queue->tail->m_next = last;
+	queue->tail = last;	/* 'last' is the new last in line */
   }
 }
 
@@ -30,7 +37,7 @@ mthread_queue_t *queue;		/* Queue that has to be initialized */
 {
 /* Initialize queue to a known state */
 
-  queue->head = queue->tail = NO_THREAD;
+  queue->head = queue->tail = NULL;
 }
 
 
@@ -40,7 +47,7 @@ mthread_queue_t *queue;		/* Queue that has to be initialized */
 PUBLIC int mthread_queue_isempty(queue)
 mthread_queue_t *queue;
 {
-  return(queue->head == NO_THREAD);
+  return(queue->head == NULL);
 }
 
 
@@ -51,23 +58,28 @@ PUBLIC void mthread_dump_queue(queue)
 mthread_queue_t *queue;
 {
   int threshold, count = 0;
-  mthread_thread_t t;
+  mthread_tcb_t *t;
+  mthread_thread_t tid;
   threshold = no_threads;
 #ifdef MDEBUG
   printf("Dumping queue: ");
 #endif
-  if(queue->head != NO_THREAD) {
+  if(queue->head != NULL) {
   	t = queue->head;
+	if (t == &mainthread) tid = MAIN_THREAD;
+	else tid = t->m_tid;
 #ifdef MDEBUG
-	printf("%d ", t);
+	printf("%d ", tid);
 #endif
 	count++;
-	t = threads[t].m_next;
-	while (t != NO_THREAD) {
+	t = t->m_next; 
+	while (t != NULL) {
+		if (t == &mainthread) tid = MAIN_THREAD;
+		else tid = t->m_tid;
 #ifdef MDEBUG
-		printf("%d ", t);
+		printf("%d ", tid);
 #endif
-		t = threads[t].m_next;
+		t = t->m_next; 
 		count++;
 		if (count > threshold) break;
 	}
@@ -90,14 +102,25 @@ PUBLIC mthread_thread_t mthread_queue_remove(queue)
 mthread_queue_t *queue;		/* Queue we want a thread from */
 {
 /* Get the first thread in this queue, if there is one. */
-  mthread_thread_t thread = queue->head;
+  mthread_thread_t thread;
+  mthread_tcb_t *tcb;
+
+  /* Calculate thread id from queue head */
+  if (queue->head == NULL) thread = NO_THREAD;
+  else if (queue->head == &mainthread) thread = MAIN_THREAD;
+  else thread = (queue->head->m_tid);
 
   if (thread != NO_THREAD) { /* i.e., this queue is not empty */
-	if (queue->head == queue->tail) /* Queue holds only one thread */
-		queue->head = queue->tail = NO_THREAD; /*So mark thread empty*/
-	else
+  	tcb = queue->head;
+	if (queue->head == queue->tail) {
+		/* Queue holds only one thread */
+		queue->head = queue->tail = NULL; /* So mark thread empty */
+	} else {
 		/* Second thread in line is the new first */
-		queue->head = threads[thread].m_next;
+		queue->head = queue->head->m_next;
+	}
+
+	tcb->m_next = NULL; /* This thread is no longer part of a queue */
   }
 
   return(thread);