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.. 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
