kernel/thread: Must always initialize is_idle field

Our thread struct gets initialized piecewise in a bunch of locations
(this is sort of a design flaw).  The is_idle field, which was
introduced to identify idle threads in SMP (where there can be more
than one), was correctly set for idle threads but was being left
uninitialized elsewhere, and in a tiny handful of cases was turning up
nonzero.

The case in pipes. was particularly vexsome, as that isn't a thread at
all but one of the "dummy" threads used for timeouts (another design
flaw IMHO).

Get this right everywhere.

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

kernel/init.c

@@ -310,14 +310,14 @@ void __weak main(void)
 #if defined(CONFIG_MULTITHREADING)
 static void init_idle_thread(struct k_thread *thr, k_thread_stack_t *stack)
 {
-#ifdef CONFIG_SMP
-	thr->base.is_idle = 1U;
-#endif
-
 	z_setup_new_thread(thr, stack,
 			  IDLE_STACK_SIZE, idle, NULL, NULL, NULL,
 			  K_LOWEST_THREAD_PRIO, K_ESSENTIAL, IDLE_THREAD_NAME);
 	z_mark_thread_as_started(thr);
+
+#ifdef CONFIG_SMP
+	thr->base.is_idle = 1U;
+#endif
 }
 #endif /* CONFIG_MULTITHREADING */
 

kernel/pipes.c

@@ -767,6 +767,9 @@ void k_pipe_block_put(struct k_pipe *pipe, struct k_mem_block *block,
 	async_desc->desc.copy_block = *block;
 	async_desc->desc.sem = sem;
 	async_desc->thread.prio = k_thread_priority_get(_current);
+#ifdef CONFIG_SMP
+	async_desc->thread.is_idle = 0;
+#endif
 
 	(void) z_pipe_put_internal(pipe, async_desc, block->data,
 				    bytes_to_write, &dummy_bytes_written,

kernel/thread.c

@@ -775,6 +775,10 @@ void z_init_thread_base(struct _thread_base *thread_base, int priority,
 
 	thread_base->sched_locked = 0U;
 
+#ifdef CONFIG_SMP
+	thread_base->is_idle = 0;
+#endif
+
 	/* swap_data does not need to be initialized */
 
 	z_init_thread_timeout(thread_base);