[tip:sched/core] sched/core: Add debugging code to catch missing update_rq_clock() calls

[Sachin Sant]

> On 02-Feb-2017, at 9:25 PM, Peter Zijlstra <peterz at infradead.org> wrote:
> 
> On Tue, Jan 31, 2017 at 10:22:47AM -0700, Ross Zwisler wrote:
>> On Tue, Jan 31, 2017 at 4:48 AM, Mike Galbraith <efault at gmx.de> wrote:
>>> On Tue, 2017-01-31 at 16:30 +0530, Sachin Sant wrote:
> 
> 
> Could some of you test this? It seems to cure things in my (very)
> limited testing.
> 

I ran few cycles of cpu hot(un)plug tests. In most cases it works except one
where I ran into rcu stall:

[  173.493453] INFO: rcu_sched detected stalls on CPUs/tasks:
[  173.493473] 	8-...: (2 GPs behind) idle=006/140000000000000/0 softirq=0/0 fqs=2996 
[  173.493476] 	(detected by 0, t=6002 jiffies, g=885, c=884, q=6350)
[  173.493482] Task dump for CPU 8:
[  173.493484] cpuhp/8         R  running task        0  3416      2 0x00000884
[  173.493489] Call Trace:
[  173.493492] [c0000004f7b834a0] [c0000004f7b83560] 0xc0000004f7b83560 (unreliable)
[  173.493498] [c0000004f7b83670] [c000000000008d28] alignment_common+0x128/0x130
[  173.493503] --- interrupt: 600 at _raw_spin_lock+0x2c/0xc0
[  173.493503]     LR = try_to_wake_up+0x204/0x5c0
[  173.493507] [c0000004f7b83960] [c0000004f4d8084c] 0xc0000004f4d8084c (unreliable)
[  173.493511] [c0000004f7b83990] [c0000000000fef54] try_to_wake_up+0x204/0x5c0
[  173.493515] [c0000004f7b83a10] [c0000000000e2b88] create_worker+0x148/0x250
[  173.493519] [c0000004f7b83ab0] [c0000000000e6e1c] alloc_unbound_pwq+0x3bc/0x4c0
[  173.493522] [c0000004f7b83b10] [c0000000000e7084] wq_update_unbound_numa+0x164/0x270
[  173.493526] [c0000004f7b83bb0] [c0000000000e8990] workqueue_online_cpu+0x250/0x3b0
[  173.493529] [c0000004f7b83c70] [c0000000000c2758] cpuhp_invoke_callback+0x148/0x5b0
[  173.493533] [c0000004f7b83ce0] [c0000000000c2df8] cpuhp_up_callbacks+0x48/0x140
[  173.493536] [c0000004f7b83d30] [c0000000000c3e98] cpuhp_thread_fun+0x148/0x180
[  173.493540] [c0000004f7b83d60] [c0000000000f3930] smpboot_thread_fn+0x290/0x2a0
[  173.493544] [c0000004f7b83dc0] [c0000000000edb3c] kthread+0x14c/0x190
[  173.493547] [c0000004f7b83e30] [c00000000000b4e8] ret_from_kernel_thread+0x5c/0x74
[  243.913715] INFO: task kworker/0:2:380 blocked for more than 120 seconds.
[  243.913732]       Not tainted 4.10.0-rc6-next-20170202 #6
[  243.913735] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  243.913738] kworker/0:2     D    0   380      2 0x00000800
[  243.913746] Workqueue: events vmstat_shepherd
[  243.913748] Call Trace:
[  243.913752] [c0000000ff07f820] [c00000000011135c] enqueue_entity+0x81c/0x1200 (unreliable)
[  243.913757] [c0000000ff07f9f0] [c00000000001a660] __switch_to+0x300/0x400
[  243.913762] [c0000000ff07fa50] [c0000000008df4f4] __schedule+0x314/0xb10
[  243.913766] [c0000000ff07fb20] [c0000000008dfd30] schedule+0x40/0xb0
[  243.913769] [c0000000ff07fb50] [c0000000008e02b8] schedule_preempt_disabled+0x18/0x30
[  243.913773] [c0000000ff07fb70] [c0000000008e1654] __mutex_lock.isra.6+0x1a4/0x660
[  243.913777] [c0000000ff07fc00] [c0000000000c3828] get_online_cpus+0x48/0x90
[  243.913780] [c0000000ff07fc30] [c00000000025fd78] vmstat_shepherd+0x38/0x150
[  243.913784] [c0000000ff07fc80] [c0000000000e5794] process_one_work+0x1a4/0x4d0
[  243.913788] [c0000000ff07fd20] [c0000000000e5b58] worker_thread+0x98/0x5a0
[  243.913791] [c0000000ff07fdc0] [c0000000000edb3c] kthread+0x14c/0x190
[  243.913795] [c0000000ff07fe30] [c00000000000b4e8] ret_from_kernel_thread+0x5c/0x74
[  243.913824] INFO: task drmgr:3413 blocked for more than 120 seconds.
[  243.913826]       Not tainted 4.10.0-rc6-next-20170202 #6
[  243.913829] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  243.913831] drmgr           D    0  3413   3114 0x00040080
[  243.913834] Call Trace:
[  243.913836] [c000000257ff3380] [c000000257ff3440] 0xc000000257ff3440 (unreliable)
[  243.913840] [c000000257ff3550] [c00000000001a660] __switch_to+0x300/0x400
[  243.913844] [c000000257ff35b0] [c0000000008df4f4] __schedule+0x314/0xb10
[  243.913847] [c000000257ff3680] [c0000000008dfd30] schedule+0x40/0xb0
[  243.913851] [c000000257ff36b0] [c0000000008e4594] schedule_timeout+0x274/0x470
[  243.913855] [c000000257ff37b0] [c0000000008e0efc] wait_for_common+0x1ac/0x2c0
[  243.913858] [c000000257ff3830] [c0000000000c50e4] bringup_cpu+0x84/0xe0
[  243.913862] [c000000257ff3860] [c0000000000c2758] cpuhp_invoke_callback+0x148/0x5b0
[  243.913865] [c000000257ff38d0] [c0000000000c2df8] cpuhp_up_callbacks+0x48/0x140
[  243.913868] [c000000257ff3920] [c0000000000c5438] _cpu_up+0xe8/0x1c0
[  243.913872] [c000000257ff3980] [c0000000000c5630] do_cpu_up+0x120/0x150
[  243.913876] [c000000257ff3a00] [c0000000005c005c] cpu_subsys_online+0x5c/0xe0
[  243.913879] [c000000257ff3a50] [c0000000005b7d84] device_online+0xb4/0x120
[  243.913883] [c000000257ff3a90] [c000000000093424] dlpar_online_cpu+0x144/0x1e0
[  243.913887] [c000000257ff3b50] [c000000000093c08] dlpar_cpu_add+0x108/0x2f0
[  243.913891] [c000000257ff3be0] [c0000000000948dc] dlpar_cpu_probe+0x3c/0x80
[  243.913894] [c000000257ff3c20] [c0000000000207a8] arch_cpu_probe+0x38/0x60
[  243.913898] [c000000257ff3c40] [c0000000005c0880] cpu_probe_store+0x40/0x70
[  243.913902] [c000000257ff3c70] [c0000000005b2e94] dev_attr_store+0x34/0x60
[  243.913906] [c000000257ff3c90] [c0000000003b0fc4] sysfs_kf_write+0x64/0xa0
[  243.913910] [c000000257ff3cb0] [c0000000003afd10] kernfs_fop_write+0x170/0x250
[  243.913914] [c000000257ff3d00] [c0000000002fb0f0] __vfs_write+0x40/0x1c0
[  243.913917] [c000000257ff3d90] [c0000000002fcba8] vfs_write+0xc8/0x240
[  243.913921] [c000000257ff3de0] [c0000000002fe790] SyS_write+0x60/0x110
[  243.913924] [c000000257ff3e30] [c00000000000b184] system_call+0x38/0xe0
[  243.913929] INFO: task ppc64_cpu:3423 blocked for more than 120 seconds.
[  243.913931]       Not tainted 4.10.0-rc6-next-20170202 #6
[  243.913933] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

Thanks
-Sachin