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Date:	Thu, 27 Sep 2012 10:59:16 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	paulmck@...ux.vnet.ibm.com, Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	Peter Zijlstra <peterz@...radead.org>,
	Tejun Heo <tj@...nel.org>,
	"Liu, Chuansheng" <chuansheng.liu@...el.com>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...64.org>,
	Fengguang Wu <fengguang.wu@...el.com>, hpa@...or.com,
	x86@...nel.org
Subject: Re: WARNING: at kernel/rcutree.c:1558 rcu_do_batch+0x386/0x3a0(),
 during CPU hotplug

On 09/26/2012 05:35 PM, Srivatsa S. Bhat wrote:
> On 09/13/2012 06:17 PM, Srivatsa S. Bhat wrote:
>> On 09/13/2012 12:00 PM, Michael Wang wrote:
>>> On 09/12/2012 11:31 PM, Paul E. McKenney wrote:
>>>> On Wed, Sep 12, 2012 at 06:06:20PM +0530, Srivatsa S. Bhat wrote:
>>>>> On 07/19/2012 10:45 PM, Paul E. McKenney wrote:
>>>>>> On Thu, Jul 19, 2012 at 05:39:30PM +0530, Srivatsa S. Bhat wrote:
>>>>>>> Hi Paul,
>>>>>>>
>>>>>>> While running a CPU hotplug stress test on v3.5-rc7+
>>>>>>> (mainline commit 8a7298b7805ab) I hit this warning.
>>>>>>> I haven't tried to debug this yet...
>>>>>>>
>>>>>>> Line number 1550 maps to:
>>>>>>>
>>>>>>> WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
>>>>>>>
>>>>>>> inside rcu_do_batch().
>>>>>>
>>>>>> Hello, Srivatsa,
>>>>>>
>>>>>> I believe that you need commit a16b7a69 (Prevent __call_rcu() from
>>>>>> invoking RCU core on offline CPUs), which is currently in -tip, queued
>>>>>> for 3.6.  Please see below for the patch.
>>>>>>
>>>>>> Does this help?
>>>>>>
>>>>>
>>>>> Hi Paul,
>>>>>
>>>>> I am hitting the cpu_is_offline() warning in rcu_do_batch() (see 2 of the
>>>>> examples below) occasionally while testing CPU hotplug on Thomas' smp/hotplug
>>>>> branch in -tip. It does contain the commit that you had mentioned above.
>>>>>
>>>>> The stack trace suggests that we are not hitting this from the __call_rcu()
>>>>> path. So I guess this needs a different fix?
>>>>
>>>> So there was an interrupt from stop_machine_stop().  Because RCU complained
>>>> about offline, I presume that this was on exit from stop_machine_stop().
>>>> (Otherwise, on entry to stop_machine_stop(), the CPU has not yet marked
>>>> itself offline, right?)
>>>>
>>
>> Yes, that's my understanding too.
>>
>>>> So my question is:  Why didn't the CPU shut off all interrupts before
>>>> coming out of stop_machine_stop()?
>>>>
>>>> Or am I confused about what is really happening here?
>>>
> 
> The interesting thing is that in every single instance of an interrupt hitting
> an offline CPU, the IP points to the statement : local_irq_restore(flags)
> in stop_machine_cpu_stop(). And the most common case of such an interrupt is the
> APIC timer interrupt (though I have also seen a few instances of do_IRQ() (device
> interrupts) in some of my stacktraces).
> 
> So, I'm inclined to conclude that the functions responsible for clearing interrupts
> during CPU offline, such as clear_local_APIC() and friends are not doing their
> job properly..

Agree, "we try to shut down apic but failed", that's may be the reason.

I think we need some help from the experts on apic code now(or don't do
any job in do_IRQ if cpu is offline, but a bad solution)...

Regards,
Michael Wang

> 
> Below are results from some of my CPU hotplug tests, in which I had added debug
> print statements and WARN_ON()s to catch situations where interrupts hit offline
> CPUs.
> (Address <ffffffff810cf8aa> corresponds to line no. 481 in kernel/stop_machine.c,
> ie., local_irq_restore(flags) in stop_machine_cpu_stop()).
> 
> Regards,
> Srivatsa S. Bhat
> 
> ---------------
> 
> [ 4730.906259] smpboot: Booting Node 1 Processor 6 APIC 0x14
> [ 4731.018008] SMP alternatives: lockdep: fixing up alternatives
> [ 4731.023811] smpboot: Booting Node 1 Processor 7 APIC 0x16
> [ 4731.132009] SMP Apic timer interrupt to offline CPU! 8
> [ 4731.132009] ------------[ cut here ]------------
> [ 4731.132009] WARNING: at arch/x86/kernel/apic/apic.c:904 smp_apic_timer_interrupt+0xc9/0xd0()
> [ 4731.132009] Hardware name: IBM System x -[7870C4Q]-
> [ 4731.132009] Modules linked in: ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf fuse loop dm_mod iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm cdc_ether crc32c_intel i7core_edac shpchp usbnet pcspkr edac_core microcode tpm_tis mii bnx2 serio_raw lpc_ich mfd_core i2c_i801 pci_hotplug i2c_core tpm ioatdma dca tpm_bios sg button rtc_cmos uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif edd ext3 mbcache jbd fan processor mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
> [ 4731.132009] Pid: 12843, comm: migration/8 Not tainted 3.6.0-rc7-warn-cpu-interrupt-0.0.0.28.36b5ec9-default #3
> [ 4731.132009] Call Trace:
> [ 4731.132009]  <IRQ>  [<ffffffff81028f99>] ? smp_apic_timer_interrupt+0xc9/0xd0
> [ 4731.132009]  [<ffffffff81028f99>] ? smp_apic_timer_interrupt+0xc9/0xd0
> [ 4731.132009]  [<ffffffff810433ea>] warn_slowpath_common+0x7a/0xb0
> [ 4731.132009]  [<ffffffff81043435>] warn_slowpath_null+0x15/0x20
> [ 4731.132009]  [<ffffffff81028f99>] smp_apic_timer_interrupt+0xc9/0xd0
> [ 4731.132009]  [<ffffffff814c662f>] apic_timer_interrupt+0x6f/0x80
> [ 4731.132009]  <EOI>  [<ffffffff810cf8aa>] ? stop_machine_cpu_stop+0xda/0x130
> [ 4731.132009]  [<ffffffff810cf7d0>] ? stop_one_cpu_nowait+0x50/0x50
> [ 4731.132009]  [<ffffffff810cf4e9>] cpu_stopper_thread+0xd9/0x1b0
> [ 4731.132009]  [<ffffffff814bc98f>] ? _raw_spin_unlock_irqrestore+0x3f/0x80
> [ 4731.132009]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4731.132009]  [<ffffffff810ac36d>] ? trace_hardirqs_on_caller+0x12d/0x1b0
> [ 4731.132009]  [<ffffffff810ac3fd>] ? trace_hardirqs_on+0xd/0x10
> [ 4731.132009]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4731.132009]  [<ffffffff8106df0e>] kthread+0x9e/0xb0
> [ 4731.132009]  [<ffffffff814c6cc4>] kernel_thread_helper+0x4/0x10
> [ 4731.132009]  [<ffffffff814bcd30>] ? retint_restore_args+0x13/0x13
> [ 4731.132009]  [<ffffffff8106de70>] ? __init_kthread_worker+0x70/0x70
> [ 4731.132009]  [<ffffffff814c6cc0>] ? gs_change+0x13/0x13
> [ 4731.132009] ---[ end trace 4591bad96b0e5f4b ]---
> [ 4731.440036] smpboot: CPU 8 is now offline
> [ 4731.485506] smpboot: CPU 9 is now offline
> [ 4731.533459] smpboot: CPU 10 is now offline
> [ 4731.591316] smpboot: CPU 11 is now offline
> [ 4731.616017] CPU 3 MCA banks CMCI:2 CMCI:3 CMCI:5
> [ 4731.729817] smpboot: CPU 12 is now offline
> [ 4731.748034] CPU 4 MCA banks CMCI:2 CMCI:3 CMCI:5 CMCI:6 CMCI:8
> [ 4731.800110] smpboot: CPU 13 is now offline
> 
> 
> [ 4909.232645] SMP alternatives: lockdep: fixing up alternatives
> [ 4909.238633] smpboot: Booting Node 1 Processor 7 APIC 0x16
> [ 4909.350250] smpboot: CPU 8 is now offline
> [ 4909.395118] Broke affinity for irq 3
> [ 4909.400743] smpboot: CPU 9 is now offline
> [ 4909.444681] smpboot: CPU 10 is now offline
> [ 4909.496011] SMP Apic timer interrupt to offline CPU! 11
> [ 4909.496011] ------------[ cut here ]------------
> [ 4909.496011] WARNING: at arch/x86/kernel/apic/apic.c:904 smp_apic_timer_interrupt+0xc9/0xd0()
> [ 4909.496011] Hardware name: IBM System x -[7870C4Q]-
> [ 4909.496011] Modules linked in: ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf fuse loop dm_mod iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm cdc_ether crc32c_intel i7core_edac shpchp usbnet pcspkr edac_core microcode tpm_tis mii bnx2 serio_raw lpc_ich mfd_core i2c_i801 pci_hotplug i2c_core tpm ioatdma dca tpm_bios sg button rtc_cmos uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif edd ext3 mbcache jbd fan processor mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
> [ 4909.496011] Pid: 10241, comm: migration/11 Tainted: G        W    3.6.0-rc7-warn-cpu-interrupt-0.0.0.28.36b5ec9-default #3
> [ 4909.496011] Call Trace:
> [ 4909.496011]  <IRQ>  [<ffffffff81028f99>] ? smp_apic_timer_interrupt+0xc9/0xd0
> [ 4909.496011]  [<ffffffff81028f99>] ? smp_apic_timer_interrupt+0xc9/0xd0
> [ 4909.496011]  [<ffffffff810433ea>] warn_slowpath_common+0x7a/0xb0
> [ 4909.496011]  [<ffffffff81043435>] warn_slowpath_null+0x15/0x20
> [ 4909.496011]  [<ffffffff81028f99>] smp_apic_timer_interrupt+0xc9/0xd0
> [ 4909.496011]  [<ffffffff814c662f>] apic_timer_interrupt+0x6f/0x80
> [ 4909.496011]  <EOI>  [<ffffffff810cf8aa>] ? stop_machine_cpu_stop+0xda/0x130
> [ 4909.496011]  [<ffffffff810cf7d0>] ? stop_one_cpu_nowait+0x50/0x50
> [ 4909.496011]  [<ffffffff810cf4e9>] cpu_stopper_thread+0xd9/0x1b0
> [ 4909.496011]  [<ffffffff814bc98f>] ? _raw_spin_unlock_irqrestore+0x3f/0x80
> [ 4909.496011]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4909.496011]  [<ffffffff810ac36d>] ? trace_hardirqs_on_caller+0x12d/0x1b0
> [ 4909.496011]  [<ffffffff810ac3fd>] ? trace_hardirqs_on+0xd/0x10
> [ 4909.496011]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4909.496011]  [<ffffffff8106df0e>] kthread+0x9e/0xb0
> [ 4909.496011]  [<ffffffff814c6cc4>] kernel_thread_helper+0x4/0x10
> [ 4909.496011]  [<ffffffff814bcd30>] ? retint_restore_args+0x13/0x13
> [ 4909.496011]  [<ffffffff8106de70>] ? __init_kthread_worker+0x70/0x70
> [ 4909.496011]  [<ffffffff814c6cc0>] ? gs_change+0x13/0x13
> [ 4909.496011] ---[ end trace 4591bad96b0e5f4c ]---
> [ 4909.703691] ------------[ cut here ]------------
> [ 4909.708124] WARNING: at kernel/rcutree.c:1560 rcu_do_batch+0x386/0x3a0()
> [ 4909.708124] Hardware name: IBM System x -[7870C4Q]-
> [ 4909.708124] Modules linked in: ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf fuse loop dm_mod iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm cdc_ether crc32c_intel i7core_edac shpchp usbnet pcspkr edac_core microcode tpm_tis mii bnx2 serio_raw lpc_ich mfd_core i2c_i801 pci_hotplug i2c_core tpm ioatdma dca tpm_bios sg button rtc_cmos uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif edd ext3 mbcache jbd fan processor mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
> [ 4909.708124] Pid: 10241, comm: migration/11 Tainted: G        W    3.6.0-rc7-warn-cpu-interrupt-0.0.0.28.36b5ec9-default #3
> [ 4909.708124] Call Trace:
> [ 4909.708124]  <IRQ>  [<ffffffff810e7336>] ? rcu_do_batch+0x386/0x3a0
> [ 4909.708124]  [<ffffffff810e7336>] ? rcu_do_batch+0x386/0x3a0
> [ 4909.708124]  [<ffffffff810433ea>] warn_slowpath_common+0x7a/0xb0
> [ 4909.708124]  [<ffffffff81043435>] warn_slowpath_null+0x15/0x20
> [ 4909.708124]  [<ffffffff810e7336>] rcu_do_batch+0x386/0x3a0
> [ 4909.708124]  [<ffffffff810ac2b0>] ? trace_hardirqs_on_caller+0x70/0x1b0
> [ 4909.708124]  [<ffffffff810ac3fd>] ? trace_hardirqs_on+0xd/0x10
> [ 4909.708124]  [<ffffffff810e8c73>] __rcu_process_callbacks+0x1a3/0x200
> [ 4909.708124]  [<ffffffff810e8d58>] rcu_process_callbacks+0x88/0x240
> [ 4909.708124]  [<ffffffff8104dcb9>] __do_softirq+0x159/0x400
> [ 4909.708124]  [<ffffffff814c6dbc>] call_softirq+0x1c/0x30
> [ 4909.708124]  [<ffffffff81004525>] do_softirq+0x95/0xd0
> [ 4909.708124]  [<ffffffff8104d785>] irq_exit+0xe5/0x100
> [ 4909.708124]  [<ffffffff81028f51>] smp_apic_timer_interrupt+0x81/0xd0
> [ 4909.708124]  [<ffffffff814c662f>] apic_timer_interrupt+0x6f/0x80
> [ 4909.708124]  <EOI>  [<ffffffff810cf8aa>] ? stop_machine_cpu_stop+0xda/0x130
> [ 4909.708124]  [<ffffffff810cf7d0>] ? stop_one_cpu_nowait+0x50/0x50
> [ 4909.708124]  [<ffffffff810cf4e9>] cpu_stopper_thread+0xd9/0x1b0
> [ 4909.708124]  [<ffffffff814bc98f>] ? _raw_spin_unlock_irqrestore+0x3f/0x80
> [ 4909.708124]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4909.708124]  [<ffffffff810ac36d>] ? trace_hardirqs_on_caller+0x12d/0x1b0
> [ 4909.708124]  [<ffffffff810ac3fd>] ? trace_hardirqs_on+0xd/0x10
> [ 4909.708124]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4909.708124]  [<ffffffff8106df0e>] kthread+0x9e/0xb0
> [ 4909.708124]  [<ffffffff814c6cc4>] kernel_thread_helper+0x4/0x10
> [ 4909.708124]  [<ffffffff814bcd30>] ? retint_restore_args+0x13/0x13
> [ 4909.708124]  [<ffffffff8106de70>] ? __init_kthread_worker+0x70/0x70
> [ 4909.708124]  [<ffffffff814c6cc0>] ? gs_change+0x13/0x13
> [ 4909.708124] ---[ end trace 4591bad96b0e5f4d ]---
> [ 4909.812522] smpboot: CPU 11 is now offline
> 
> 
> [ 4974.727112] smpboot: CPU 12 is now offline
> [ 4974.737763] CPU 4 MCA banks CMCI:2 CMCI:3 CMCI:5 CMCI:6 CMCI:8
> [ 4974.896043] smpboot: CPU 13 is now offline
> [ 4974.903566] CPU 5 MCA banks CMCI:2 CMCI:3 CMCI:5
> [ 4974.968010] SMP Apic timer interrupt to offline CPU! 14
> [ 4974.968010] ------------[ cut here ]------------
> [ 4974.968010] WARNING: at arch/x86/kernel/apic/apic.c:904 smp_apic_timer_interrupt+0xc9/0xd0()
> [ 4974.968010] Hardware name: IBM System x -[7870C4Q]-
> [ 4974.968010] Modules linked in: ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf fuse loop dm_mod iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm cdc_ether crc32c_intel i7core_edac shpchp usbnet pcspkr edac_core microcode tpm_tis mii bnx2 serio_raw lpc_ich mfd_core i2c_i801 pci_hotplug i2c_core tpm ioatdma dca tpm_bios sg button rtc_cmos uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif edd ext3 mbcache jbd fan processor mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
> [ 4974.968010] Pid: 20651, comm: migration/14 Tainted: G        W    3.6.0-rc7-warn-cpu-interrupt-0.0.0.28.36b5ec9-default #3
> [ 4974.968010] Call Trace:
> [ 4974.968010]  <IRQ>  [<ffffffff81028f99>] ? smp_apic_timer_interrupt+0xc9/0xd0
> [ 4974.968010]  [<ffffffff81028f99>] ? smp_apic_timer_interrupt+0xc9/0xd0
> [ 4974.968010]  [<ffffffff810433ea>] warn_slowpath_common+0x7a/0xb0
> [ 4974.968010]  [<ffffffff81043435>] warn_slowpath_null+0x15/0x20
> [ 4974.968010]  [<ffffffff81028f99>] smp_apic_timer_interrupt+0xc9/0xd0
> [ 4974.968010]  [<ffffffff814c662f>] apic_timer_interrupt+0x6f/0x80
> [ 4974.968010]  <EOI>  [<ffffffff810cf8aa>] ? stop_machine_cpu_stop+0xda/0x130
> [ 4974.968010]  [<ffffffff810cf7d0>] ? stop_one_cpu_nowait+0x50/0x50
> [ 4974.968010]  [<ffffffff810cf4e9>] cpu_stopper_thread+0xd9/0x1b0
> [ 4974.968010]  [<ffffffff814bc98f>] ? _raw_spin_unlock_irqrestore+0x3f/0x80
> [ 4974.968010]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4974.968010]  [<ffffffff810ac36d>] ? trace_hardirqs_on_caller+0x12d/0x1b0
> [ 4974.968010]  [<ffffffff810ac3fd>] ? trace_hardirqs_on+0xd/0x10
> [ 4974.968010]  [<ffffffff810cf410>] ? res_counter_init+0x50/0x50
> [ 4974.968010]  [<ffffffff8106df0e>] kthread+0x9e/0xb0
> [ 4974.968010]  [<ffffffff814c6cc4>] kernel_thread_helper+0x4/0x10
> [ 4974.968010]  [<ffffffff814bcd30>] ? retint_restore_args+0x13/0x13
> [ 4974.968010]  [<ffffffff8106de70>] ? __init_kthread_worker+0x70/0x70
> [ 4974.968010]  [<ffffffff814c6cc0>] ? gs_change+0x13/0x13
> [ 4974.968010] ---[ end trace 4591bad96b0e5f4e ]---
> [ 4975.179145] smpboot: CPU 14 is now offline
> 
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