p4wq: Add Kconfig to perform early init on threads

In order to make them functional for devices during init. Default
behavior is to keep late initialization, as before.

Signed-off-by: Luis Ubieda <luisf@croxel.com>

lib/os/Kconfig

@@ -106,6 +106,16 @@ config MPSC_CLEAR_ALLOCATED
 	  When enabled packet space is zeroed before returning from allocation.
 endif
 
+if SCHED_DEADLINE
+
+config P4WQ_INIT_STAGE_EARLY
+	bool "Early initialization of P4WQ threads"
+	help
+	  Initialize P4WQ threads early so that the P4WQ can be used on devices
+	  initialization sequence.
+
+endif
+
 config REBOOT
 	bool "Reboot functionality"
 	help

lib/os/p4wq.c

@@ -218,7 +218,11 @@ void k_p4wq_enable_static_thread(struct k_p4wq *queue, struct k_thread *thread,
  * so they can initialize in parallel instead of serially on the main
  * CPU.
  */
+#if defined(CONFIG_P4WQ_INIT_STAGE_EARLY)
+SYS_INIT(static_init, POST_KERNEL, 1);
+#else
 SYS_INIT(static_init, APPLICATION, 99);
+#endif
 
 void k_p4wq_submit(struct k_p4wq *queue, struct k_p4wq_work *item)
 {