[Devel] [PATCH v2 vz8] kernel/sched/fair.c: Add missing update_rq_clock() calls

[Andrey Ryabinin]

We've got a hard lockup which seems to be caused by mgag200
console printk code calling to schedule_work from scheduler
with rq->lock held:
  #5 [ffffb79e034239a8] native_queued_spin_lock_slowpath at ffffffff8b50c6c6
  #6 [ffffb79e034239a8] _raw_spin_lock at ffffffff8bc96e5c
  #7 [ffffb79e034239b0] try_to_wake_up at ffffffff8b4e26ff
  #8 [ffffb79e03423a10] __queue_work at ffffffff8b4ce3f3
  #9 [ffffb79e03423a58] queue_work_on at ffffffff8b4ce714
 #10 [ffffb79e03423a68] mga_imageblit at ffffffffc026d666 [mgag200]
 #11 [ffffb79e03423a80] soft_cursor at ffffffff8b8a9d84
 #12 [ffffb79e03423ad8] bit_cursor at ffffffff8b8a99b2
 #13 [ffffb79e03423ba0] hide_cursor at ffffffff8b93bc7a
 #14 [ffffb79e03423bb0] vt_console_print at ffffffff8b93e07d
 #15 [ffffb79e03423c18] console_unlock at ffffffff8b518f0e
 #16 [ffffb79e03423c68] vprintk_emit_log at ffffffff8b51acf7
 #17 [ffffb79e03423cc0] vprintk_default at ffffffff8b51adcd
 #18 [ffffb79e03423cd0] printk at ffffffff8b51b3d6
 #19 [ffffb79e03423d30] __warn_printk at ffffffff8b4b13a0
 #20 [ffffb79e03423d98] assert_clock_updated at ffffffff8b4dd293
 #21 [ffffb79e03423da0] deactivate_task at ffffffff8b4e12d1
 #22 [ffffb79e03423dc8] move_task_group at ffffffff8b4eaa5b
 #23 [ffffb79e03423e00] cpulimit_balance_cpu_stop at ffffffff8b4f02f3
 #24 [ffffb79e03423eb0] cpu_stopper_thread at ffffffff8b576b67
 #25 [ffffb79e03423ee8] smpboot_thread_fn at ffffffff8b4d9125
 #26 [ffffb79e03423f10] kthread at ffffffff8b4d4fc2
 #27 [ffffb79e03423f50] ret_from_fork at ffffffff8be00255

The printk called because assert_clock_updated() triggered
	SCHED_WARN_ON(rq->clock_update_flags < RQCF_ACT_SKIP);

This means that we missing necessary update_rq_clock() call.
Add one to cpulimit_balance_cpu_stop() to fix the warning.
Also add one in load_balance() before move_task_groups() call.
It seems to be another place missing this call.

https://jira.sw.ru/browse/PSBM-108013
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5d3556b15e70..e6dc21d5fa03 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7816,6 +7816,7 @@ static int cpulimit_balance_cpu_stop(void *data)
 
 		schedstat_inc(sd->clb_count);
 
+		update_rq_clock(rq);
 		if (do_cpulimit_balance(&env))
 			schedstat_inc(sd->clb_pushed);
 		else
@@ -9176,6 +9177,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 			env.loop = 0;
 			local_irq_save(rf.flags);
 			double_rq_lock(env.dst_rq, busiest);
+			update_rq_clock(env.dst_rq);
 			cur_ld_moved = ld_moved = move_task_groups(&env);
 			double_rq_unlock(env.dst_rq, busiest);
 			local_irq_restore(rf.flags);
-- 
2.26.2