[patch 17/18] sched: Enable might_sleep() checks early

[Thomas Gleixner]

might_sleep() checks are enabled after the boot process is done. That hides
bugs in the smp bringup and driver initialization code.

Enable it right when the scheduler starts working, i.e. when init task and
kthreadd have been created and right before the idle task enables
preemption.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 init/main.c         |    2 ++
 kernel/sched/core.c |    4 +++-
 2 files changed, 5 insertions(+), 1 deletion(-)

--- a/init/main.c
+++ b/init/main.c
@@ -410,6 +410,8 @@ static noinline void __ref rest_init(voi
 	 * at least once to get things moving:
 	 */
 	init_idle_bootup_task(current);
+	/* Enable might_sleep() checks */
+	system_state = SYSTEM_BOOTING_UP;
 	schedule_preempt_disabled();
 	/* Call into cpu_idle with preempt disabled */
 	cpu_startup_entry(CPUHP_ONLINE);
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6226,8 +6226,10 @@ void ___might_sleep(const char *file, in
 
 	if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
 	     !is_idle_task(current)) ||
-	    system_state != SYSTEM_RUNNING || oops_in_progress)
+	    system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
+	    oops_in_progress)
 		return;
+
 	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
 		return;
 	prev_jiffy = jiffies;