v4.11-rc0: WARNING at kernel/sched/sched.h:812 set_next_entity on cpu hot(un)plug

[Christian Borntraeger]

While doing cpu hotunplug on s390 I got the following warning which indicates that
Matts new check is either broken or finds real bugs.


[  190.608421] rq->clock_update_flags < RQCF_ACT_SKIP
[  190.608427] ------------[ cut here ]------------
[  190.608434] WARNING: CPU: 29 PID: 153 at kernel/sched/sched.h:812 set_next_entity+0xc5e/0xc98
[  190.608435] Kernel panic - not syncing: panic_on_warn set ...

[  190.608437] CPU: 29 PID: 153 Comm: migration/29 Not tainted 4.10.0+ #377
[  190.608437] Hardware name: IBM              2964 NC9              704              (LPAR)
[  190.608438] Stack:
[  190.608438]        000000fb8ab875b8 000000fb8ab87648 0000000000000003 0000000000000000
[  190.608439]        000000fb8ab876e8 000000fb8ab87660 000000fb8ab87660 0000000000000020
[  190.608441]        000000000069dc1e 0000000000000020 000000000000000a 000000000000000a
[  190.608442]        000000000000000c 000000fb8ab876b0 0000000000000000 0000000000000000
[  190.608443]        0000000000935d60 00000000001125ec 000000fb8ab87648 000000fb8ab876a0
[  190.608444] Call Trace:
[  190.608448] ([<00000000001124a2>] show_trace+0x62/0x78)
[  190.608449]  [<0000000000112590>] show_stack+0x68/0xe0 
[  190.608453]  [<0000000000666c0e>] dump_stack+0x7e/0xb0 
[  190.608456]  [<000000000027c704>] panic+0x104/0x240 
[  190.608457]  [<0000000000140cd8>] cpuhp_invoke_callback+0x0/0x578 
[  190.608458]  [<0000000000666376>] report_bug+0xce/0x150 
[  190.608459]  [<0000000000100b10>] do_report_trap+0xf0/0x108 
[  190.608460]  [<0000000000100c7e>] illegal_op+0xc6/0x160 
[  190.608464]  [<000000000092bbfc>] pgm_check_handler+0x150/0x1a4 
[  190.608465]  [<0000000000184906>] set_next_entity+0xc5e/0xc98 
[  190.608466] ([<0000000000184902>] set_next_entity+0xc5a/0xc98)
[  190.608467]  [<000000000018a278>] pick_next_task_fair+0xa8/0x5b8 
[  190.608468]  [<0000000000176ba8>] sched_cpu_dying+0x260/0x380 
[  190.608469]  [<0000000000140d96>] cpuhp_invoke_callback+0xbe/0x578 
[  190.608470]  [<0000000000141b70>] take_cpu_down+0x88/0xe0 
[  190.608472]  [<00000000002015d6>] multi_cpu_stop+0x106/0x130 
[  190.608473]  [<000000000020188c>] cpu_stopper_thread+0xf4/0x198 
[  190.608475]  [<000000000016a754>] smpboot_thread_fn+0x134/0x1d0 
[  190.608478]  [<00000000001658ea>] kthread+0x13a/0x158 
[  190.608479]  [<000000000092baa6>] kernel_thread_starter+0x6/0xc 
[  190.608480]  [<000000000092baa0>] kernel_thread_starter+0x0/0xc 


Any immediate idea?

Christian