waitpid: use event instead of busy loop when waiting for threads to die

kernel-src/include/kernel/proc.h

@@ -36,6 +36,7 @@ typedef struct proc_t {
 	cred_t cred;
 	spinlock_t threadlistlock;
 	thread_t *threadlist;
+	eventheader_t thread_exit_event;
 	bool nomorethreads;
 	size_t runningthreadcount;
 	size_t fdcount;

kernel-src/sys/proc.c

@@ -107,6 +107,7 @@ proc_t *proc_create() {
 	itimer_init(&proc->timer.profiling, profdpc, proc);
 	SPINLOCK_INIT(proc->threadlistlock);
 	EVENT_INITHEADER(&proc->child_exit_event);
+	EVENT_INITHEADER(&proc->thread_exit_event);
 
 	proc->fd = alloc(sizeof(fd_t) * 3);
 	if (proc->fd == NULL) {
@@ -173,10 +174,18 @@ void proc_stop_other_threads() {
 		threadlist = threadlist->procnext;
 	}
 
-	while (__atomic_load_n(&proc->runningthreadcount, __ATOMIC_SEQ_CST) > 1) {
-		arch_e9_puts("proc_stop_other_threads\n");
-		sched_yield();
+	eventlistener_t listener;
+	EVENT_INITLISTENER(&listener);
+	for (;;) {
+		EVENT_ATTACH(&listener, &proc->thread_exit_event);
+		if (__atomic_load_n(&proc->runningthreadcount, __ATOMIC_SEQ_CST) == 1)
+			break;
+
+		EVENT_WAIT(&listener, 0);
+		EVENT_DETACHALL(&listener);
 	}
+	EVENT_DETACHALL(&listener);
+
 
 	proc->nomorethreads = false;
 }

kernel-src/sys/syscalls/waitpid.c

@@ -132,10 +132,19 @@ syscallret_t syscall_waitpid(context_t *context, pid_t pid, int *status, int opt
 		while (threadlist) {
 			thread_t *freethread = threadlist;
 			threadlist = threadlist->procnext;
-			volatile int *flags = (volatile int *)(&freethread->flags);
 			// wait until the thread can actually be unallocated
-			while ((*flags & THREAD_FLAGS_DEAD) == 0)
-				sched_yield();
+			eventlistener_t listener;
+			EVENT_INITLISTENER(&listener);
+			for (;;) {
+				EVENT_ATTACH(&listener, &iterator->thread_exit_event);
+				if (freethread->flags & THREAD_FLAGS_DEAD) {
+					EVENT_DETACHALL(&listener);
+					break;
+				}
+
+				EVENT_WAIT(&listener, 0);
+				EVENT_DETACHALL(&listener);
+			}
 
 			sched_destroythread(freethread);
 		}

kernel-src/sys/thread.c

@@ -70,6 +70,8 @@ static void threadexit_internal(context_t *, void *) {
 	current_cpu()->thread = NULL;
 
 	thread->flags |= THREAD_FLAGS_DEAD;
+	if (thread->proc)
+		EVENT_SIGNAL(&thread->proc->thread_exit_event);
 
 	// because a thread deallocating its own data is a nightmare, thread deallocation and such will be left to whoever frees the proc it's tied to
 	// (likely an exit(2) call)