implement child tid behavior

so3/include/thread.h

@@ -80,7 +80,7 @@ struct tcb {
 	pcb_t *pcb;
 
 	int exit_status;
-	addr_t child_clear_tid;
+	int *clear_child_tid;
 
 	struct list_head list; /* List of threads belonging to a process */
 
@@ -119,6 +119,7 @@ typedef struct {
 void threads_init(void);
 
 SYSCALL_DECLARE(exit, int exit_status);
+SYSCALL_DECLARE(set_tid_address, int *tidptr);
 
 tcb_t *kernel_thread(th_fn_t start_routine, const char *name, void *arg, uint32_t prio);
 tcb_t *user_thread(clone_args_t *args);

so3/kernel/thread.c

@@ -266,12 +266,19 @@ void thread_exit(int exit_status)
 				complete(&pcb->threads_active);
 		}
 
+		/* If clear child tid is set, inform waiting thread */
+		if (pcb && current() != pcb->main_thread) {
+			if (current()->clear_child_tid) {
+				*(current()->clear_child_tid) = 0;
+				do_futex(current()->clear_child_tid, FUTEX_WAKE, 1, NULL, NULL, 0, 0);
+			}
+		}
+
 		/* Check if this is a kernel thread OR a main thread before a image replacement (during exec()).
 		 * In this case, we do not leave the thread in zombie since we assume that no other threads are joining on it.
 		 * (This is currently a limitation: kernel threads can not join other threads).
 		 */
 #warning Kernel threads cannot join other threads!
-#warning TODO: check for clear_child_tid usage
 
 		if (current()->pcb != NULL)
 			zombie();
@@ -359,7 +366,7 @@ tcb_t *thread_create(clone_args_t *args)
 
 	flags = local_irq_save();
 
-	tcb = (tcb_t *) malloc(sizeof(tcb_t));
+	tcb = (tcb_t *) calloc(1, sizeof(tcb_t));
 
 	if (tcb == NULL) {
 		printk("%s: failed to alloc memory.\n", __func__);
@@ -405,7 +412,7 @@ tcb_t *thread_create(clone_args_t *args)
 	}
 
 	if (args->flags & CLONE_CHILD_CLEARTID)
-		tcb->child_clear_tid = (addr_t) args->child_tid;
+		tcb->clear_child_tid = args->child_tid;
 
 	local_irq_restore(flags);
 
@@ -589,6 +596,12 @@ SYSCALL_DEFINE1(exit, int, exit_status)
 	return 0;
 }
 
+SYSCALL_DEFINE1(set_tid_address, int *, tidptr)
+{
+	current()->clear_child_tid = tidptr;
+	return current()->tid;
+}
+
 void threads_init(void)
 {
 	int i;

so3/syscall.tbl

@@ -48,6 +48,7 @@ getpid                  MMU
 execve                  MMU
 fork                    MMU
 clone                   MMU
+set_tid_address         MMU
 exit                    MMU
 exit_group              MMU
 wait4                   MMU