workqueue: mark init_workqueues() as early_initcall()

Mark init_workqueues() as early_initcall() and thus it will be initialized
before smp bringup. init_workqueues() registers for the hotcpu notifier
and thus it should cope with the processors that are brought online after
the workqueues are initialized.

x86 smp bringup code uses workqueues and uses a workaround for the
cold boot process (as the workqueues are initialized post smp_init()).
Marking init_workqueues() as early_initcall() will pave the way for
cleaning up this code.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>

include/linux/workqueue.h

@@ -327,7 +327,6 @@ extern int schedule_delayed_work_on(int cpu, struct delayed_work *work,
 extern int schedule_on_each_cpu(work_func_t func);
 extern int keventd_up(void);
 
-extern void init_workqueues(void);
 int execute_in_process_context(work_func_t fn, struct execute_work *);
 
 extern int flush_work(struct work_struct *work);

init/main.c

@@ -32,7 +32,6 @@
 #include <linux/start_kernel.h>
 #include <linux/security.h>
 #include <linux/smp.h>
-#include <linux/workqueue.h>
 #include <linux/profile.h>
 #include <linux/rcupdate.h>
 #include <linux/moduleparam.h>
@@ -786,7 +785,6 @@ static void __init do_initcalls(void)
  */
 static void __init do_basic_setup(void)
 {
-	init_workqueues();
 	cpuset_init_smp();
 	usermodehelper_init();
 	init_tmpfs();

kernel/workqueue.c

@@ -3507,7 +3507,7 @@ out_unlock:
 }
 #endif /* CONFIG_FREEZER */
 
-void __init init_workqueues(void)
+static int __init init_workqueues(void)
 {
 	unsigned int cpu;
 	int i;
@@ -3559,4 +3559,6 @@ void __init init_workqueues(void)
 	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
 					    WQ_UNBOUND_MAX_ACTIVE);
 	BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq);
+	return 0;
 }
+early_initcall(init_workqueues);