kernel, xtensa: Switch-specific thread return value

When using _arch_switch() context switching, the thread return value
is a generic hook and not provided by the architecture.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>

arch/xtensa/include/kernel_arch_func.h

@@ -78,11 +78,13 @@ static ALWAYS_INLINE void kernel_arch_init(void)
  *
  * @return N/A
  */
+#if !CONFIG_USE_SWITCH
 static ALWAYS_INLINE void
 _set_thread_return_value(struct k_thread *thread, unsigned int value)
 {
 	thread->callee_saved.retval = value;
 }
+#endif
 
 extern void k_cpu_atomic_idle(unsigned int imask);
 

kernel/include/kernel_internal.h

@@ -75,6 +75,7 @@ extern void _check_stack_sentinel(void);
 static inline unsigned int _Swap(unsigned int key)
 {
 	struct k_thread *new_thread, *old_thread;
+	int ret;
 
 	old_thread = _kernel.current;
 
@@ -89,9 +90,11 @@ static inline unsigned int _Swap(unsigned int key)
 	_arch_switch(new_thread->switch_handle,
 		     &old_thread->switch_handle);
 
+	ret = _kernel.current->swap_retval;
+
 	irq_unlock(key);
 
-	return _kernel.current->swap_retval;
+	return ret;
 }
 
 #else /* !CONFIG_USE_SWITCH */

kernel/include/kernel_structs.h

@@ -138,6 +138,17 @@ extern struct _kernel _kernel;
 
 #include <kernel_arch_func.h>
 
+#if CONFIG_USE_SWITCH
+/* This is a arch function traditionally, but when the switch-based
+ * _Swap() is in use it's a simple inline provided by the kernel.
+ */
+static ALWAYS_INLINE void
+_set_thread_return_value(struct k_thread *thread, unsigned int value)
+{
+	thread->swap_retval = value;
+}
+#endif
+
 static ALWAYS_INLINE void
 _set_thread_return_value_with_data(struct k_thread *thread,
 				   unsigned int value,