kernel: fix race conditions with z_ready_thread

Several internal APIs wrote thread attributes (return value, mainly)
_after_ calling `z_ready_thread`. This is unsafe, at least in SMP,
because another core could have already picked up and run the thread.

Fixes zephyrproject-rtos#32800.

Signed-off-by: James Harris <james.harris@intel.com>

Author: jharris-intel

kernel/condvar.c

@@ -64,9 +64,9 @@ int z_impl_k_condvar_broadcast(struct k_condvar *condvar)
 	/* wake up any threads that are waiting to write */
 	while ((pending_thread = z_unpend_first_thread(&condvar->wait_q)) !=
 	       NULL) {
+		woken++;
 		arch_thread_return_value_set(pending_thread, 0);
 		z_ready_thread(pending_thread);
-		woken++;
 	}
 
 	z_reschedule(&lock, key);

kernel/futex.c

@@ -41,9 +41,9 @@ int z_impl_k_futex_wake(struct k_futex *futex, bool wake_all)
 	do {
 		thread = z_unpend_first_thread(&futex_data->wait_q);
 		if (thread) {
-			z_ready_thread(thread);
-			arch_thread_return_value_set(thread, 0);
 			woken++;
+			arch_thread_return_value_set(thread, 0);
+			z_ready_thread(thread);
 		}
 	} while (thread && wake_all);
 

kernel/stack.c

@@ -108,10 +108,10 @@ int z_impl_k_stack_push(struct k_stack *stack, stack_data_t data)
 	first_pending_thread = z_unpend_first_thread(&stack->wait_q);
 
 	if (first_pending_thread != NULL) {
-		z_ready_thread(first_pending_thread);
-
 		z_thread_return_value_set_with_data(first_pending_thread,
 						   0, (void *)data);
+
+		z_ready_thread(first_pending_thread);
 		z_reschedule(&stack->lock, key);
 		goto end;
 	} else {

kernel/timer.c

@@ -82,9 +82,9 @@ void z_timer_expiration_handler(struct _timeout *t)
 	 */
 	z_unpend_thread_no_timeout(thread);
 
-	z_ready_thread(thread);
-
 	arch_thread_return_value_set(thread, 0);
+
+	z_ready_thread(thread);
 }
 
 

lib/posix/pthread_mutex.c

@@ -142,8 +142,8 @@ int pthread_mutex_unlock(pthread_mutex_t *m)
 		if (thread) {
 			m->owner = (pthread_t)thread;
 			m->lock_count++;
-			z_ready_thread(thread);
 			arch_thread_return_value_set(thread, 0);
+			z_ready_thread(thread);
 			z_reschedule_irqlock(key);
 			return 0;
 		}