WARNING: at /home/konrad/ssd/linux/kernel/rcutree.c:1547 __rcu_process_callbacks+0x42e/0x440()
I've been getting this when booting a Xen PV guest with 3 CPUs (of which two are online). Any thoughts?
Using config file "/test.xm". Started domain latest (id=6)
[ 0.000000] console [hvc0] enabled, bootconsole disabled [ 0.000000] Xen: using vcpuop timer interface [ 0.000000] installing Xen timer for CPU 0 [ 0.000000] Detected 3093.036 MHz processor. [ 0.000999] Calibrating delay loop (skipped), value calculated using timer frequency.. 6186.07 BogoMIPS (lpj=3093036) [ 0.000999] pid_max: default: 32768 minimum: 301 [ 0.000999] Security Framework initialized [ 0.000999] SELinux: Initializing. [ 0.000999] SELinux: Starting in permissive mode [ 0.000999] Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes) [ 0.000999] Inode-cache hash table entries: 65536 (order: 7, 524288 bytes) [ 0.000999] Mount-cache hash table entries: 256 [ 0.000999] Initializing cgroup subsys cpuacct [ 0.000999] Initializing cgroup subsys freezer [ 0.000999] ENERGY_PERF_BIAS: Set to 'normal', was 'performance' [ 0.000999] ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8) [ 0.000999] CPU: Physical Processor ID: 0 [ 0.000999] CPU: Processor Core ID: 0 [ 0.000999] SMP alternatives: switching to UP code [ 0.026357] cpu 0 spinlock event irq 17 [ 0.026377] Performance Events: unsupported p6 CPU model 42 no PMU driver, software events only. [ 0.026462] NMI watchdog: disabled (cpu0): hardware events not enabled [ 0.026567] installing Xen timer for CPU 1 [ 0.026580] cpu 1 spinlock event irq 24 [ 0.026603] SMP alternatives: switching to SMP code [ 0.049557] NMI watchdog: disabled (cpu1): hardware events not enabled [ 0.049756] installing Xen timer for CPU 2 [ 0.049786] cpu 2 spinlock event irq 31 [ 0.049996] NMI watchdog: disabled (cpu2): hardware events not enabled [ 0.049996] Brought up 3 CPUs [ 0.050313] kworker/u:0 (20) used greatest stack depth: 6000 bytes left [ 0.051028] Grant tables using version 2 layout. [ 0.051065] Grant table initialized [ 0.069993] RTC time: 165:165:165, date: 165/165/65 [ 0.070103] NET: Registered protocol family 16 [ 0.070141] kworker/u:0 (24) used greatest stack depth: 5544 bytes left [ 0.073000] ------------[ cut here ]------------ [ 0.073006] WARNING: at /home/konrad/ssd/linux/kernel/rcutree.c:1547 __rcu_process_callbacks+0x42e/0x440() [ 0.073008] Modules linked in: [ 0.073010] Pid: 12, comm: migration/2 Not tainted 3.5.0-rc2 #2 [ 0.073011] Call Trace: [ 0.073017] <IRQ> [<ffffffff810718ea>] warn_slowpath_common+0x7a/0xb0 [ 0.073019] [<ffffffff81071935>] warn_slowpath_null+0x15/0x20 [ 0.073021] [<ffffffff810edb1e>] __rcu_process_callbacks+0x42e/0x440 [ 0.073023] [<ffffffff810edb50>] rcu_process_callbacks+0x20/0x40 [ 0.073025] [<ffffffff810792c9>] __do_softirq+0xa9/0x160 [ 0.073028] [<ffffffff810a1065>] ? sched_clock_local+0x25/0x90 [ 0.073030] [<ffffffff810d7201>] ? queue_stop_cpus_work+0x51/0xf0 [ 0.073033] [<ffffffff815cee1c>] call_softirq+0x1c/0x30 [ 0.073034] [<ffffffff81039435>] do_softirq+0x65/0xa0 [ 0.073036] [<ffffffff810790c5>] irq_exit+0xd5/0xf0 [ 0.073039] [<ffffffff8132347f>] xen_evtchn_do_upcall+0x2f/0x40 [ 0.073040] [<ffffffff815cee6e>] xen_do_hypervisor_callback+0x1e/0x30 [ 0.073042] <EOI> [<ffffffff810d7201>] ? queue_stop_cpus_work+0x51/0xf0 [ 0.073044] [<ffffffff8100122a>] ? hypercall_page+0x22a/0x1000 [ 0.073045] [<ffffffff8100122a>] ? hypercall_page+0x22a/0x1000 [ 0.073048] [<ffffffff8103361d>] ? xen_force_evtchn_callback+0xd/0x10 [ 0.073049] [<ffffffff81033ed2>] ? check_events+0x12/0x20 [ 0.073051] [<ffffffff81033ebf>] ? xen_restore_fl_direct_reloc+0x4/0x4 [ 0.073053] [<ffffffff810d73aa>] ? stop_machine_cpu_stop+0xba/0xf0 [ 0.073054] [<ffffffff810d72f0>] ? stop_one_cpu_nowait+0x50/0x50 [ 0.073055] [<ffffffff810d7021>] ? cpu_stopper_thread+0xf1/0x1c0 [ 0.073058] [<ffffffff815c5d7e>] ? __schedule+0x3be/0x760 [ 0.073060] [<ffffffff815c6d59>] ? _raw_spin_unlock_irqrestore+0x19/0x30 [ 0.073061] [<ffffffff810d6f30>] ? res_counter_charge+0x10/0x10 [ 0.073064] [<ffffffff81090c46>] ? kthread+0x96/0xa0 [ 0.073065] [<ffffffff815ced24>] ? kernel_thread_helper+0x4/0x10 [ 0.073067] [<ffffffff815c72b8>] ? retint_restore_args+0x5/0x6 [ 0.073069] [<ffffffff815ced20>] ? gs_change+0x13/0x13 [ 0.073073] ---[ end trace 4eaa2a86a8e2da22 ]--- [ 0.073075] dca service started, version 1.12.1 [ 0.074006] PCI: setting up Xen PCI frontend stub [ 0.074015] PCI: pci_cache_line_size set to 64 bytes [ 0.088093] bio: create slab <bio-0> at 0 [ 0.089051] ACPI: Interpreter disabled. [ 0.089063] xen/balloon: Initialising balloon driver. [ 0.091124] xen-balloon: Initialising balloon driver. [ 0.092068] vgaarb: loaded [ 0.092068] usbcore: registered new interface driver usbfs [ 0.092087] usbcore: registered new interface driver hub [ 0.093027] usbcore: registered new device driver usb [ 0.093039] PCI: System does not support PCI [ 0.093039] PCI: System does not support PCI [ 0.094043] NetLabel: Initializing [ 0.094052] NetLabel: domain hash size = 128 [ 0.094057] NetLabel: protocols = UNLABELED CIPSOv4 [ 0.094077] NetLabel: unlabeled traffic allowed by default [ 0.094099] Switching to clocksource xen [ 0.094160] pnp: PnP ACPI: disabled [ 0.101664] NET: Registered protocol family 2 [ 0.101866] IP route cache hash table entries: 32768 (order: 6, 262144 bytes) [ 0.102859] TCP established hash table entries: 131072 (order: 9, 2097152 bytes) [ 0.103661] TCP bind hash table entries: 65536 (order: 8, 1048576 bytes) [ 0.103849] TCP: Hash tables configured (established 131072 bind 65536) [ 0.103858] TCP: reno registered [ 0.103873] UDP hash table entries: 512 (order: 2, 16384 bytes) [ 0.103891] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes) [ 0.104035] NET: Registered protocol family 1 [ 0.104333] RPC: Registered named UNIX socket transport module. [ 0.104347] RPC: Registered udp transport module. [ 0.104356] RPC: Registered tcp transport module. [ 0.104362] RPC: Registered tcp NFSv4.1 backchannel transport module. [ 0.104371] PCI: CLS 0 bytes, default 64 [ 0.104511] Trying to unpack rootfs image as initramfs... [ 0.337888] Freeing initrd memory: 273152k freed [ 0.383239] platform rtc_cmos: registered platform RTC device (no PNP device found) [ 0.383418] Machine check injector initialized [ 0.384702] microcode: CPU0 sig=0x206a7, pf=0x2, revision=0x12 [ 0.384730] microcode: CPU1 sig=0x206a7, pf=0x2, revision=0x12 [ 0.384859] microcode: Microcode Update Driver: v2.00 <[email protected]>, Peter Oruba [ 0.385589] audit: initializing netlink socket (disabled) [ 0.385612] type=2000 audit(1340130254.678:1): initialized [ 0.403267] HugeTLB registered 2 MB page size, pre-allocated 0 pages [ 0.403508] VFS: Disk quotas dquot_6.5.2 [ 0.403552] Dquot-cache hash table entries: 512 (order 0, 4096 bytes) [ 0.403720] NFS: Registering the id_resolver key type [ 0.403739] Key type id_resolver registered [ 0.403882] NTFS driver 2.1.30 [Flags: R/W]. [ 0.403981] msgmni has been set to 1986 [ 0.404021] SELinux: Registering netfilter hooks [ 0.404794] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) [ 0.404806] io scheduler noop registered [ 0.404812] io scheduler deadline registered [ 0.404843] io scheduler cfq registered (default) [ 0.404993] pci_hotplug: PCI Hot Plug PCI Core version: 0.5 [ 0.405260] ioatdma: Intel(R) QuickData Technology Driver 4.00 [ 0.451143] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled [ 0.452662] Non-volatile memory driver v1.3 [ 0.452673] Linux agpgart interface v0.103 [ 0.453294] [drm] Initialized drm 1.1.0 20060810 [ 0.457300] brd: module loaded [ 0.459306] loop: module loaded [ 0.459798] Fixed MDIO Bus: probed [ 0.459807] tun: Universal TUN/TAP device driver, 1.6 [ 0.459813] tun: (C) 1999-2004 Max Krasnyansky <[email protected]> [ 0.459986] ixgbevf: Intel(R) 10 Gigabit PCI Express Virtual Function Network Driver - version 2.6.0-k [ 0.459998] ixgbevf: Copyright (c) 2009 - 2012 Intel Corporation. [ 0.460777] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver [ 0.460788] ehci_hcd: block sizes: qh 112 qtd 96 itd 192 sitd 96 [ 0.460891] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver [ 0.460901] ohci_hcd: block sizes: ed 80 td 96 [ 0.461001] uhci_hcd: USB Universal Host Controller Interface driver [ 0.461293] usbcore: registered new interface driver usblp [ 0.461392] usbcore: registered new interface driver libusual [ 0.461734] i8042: PNP: No PS/2 controller found. Probing ports directly. [ 0.462609] i8042: No controller found [ 0.462737] mousedev: PS/2 mouse device common for all mice [ 0.523312] rtc_cmos rtc_cmos: rtc core: registered rtc_cmos as rtc0 [ 0.523440] rtc_cmos: probe of rtc_cmos failed with error -38 [ 0.523679] EFI Variables Facility v0.08 2004-May-17 [ 0.523734] zram: num_devices not specified. Using default: 1 [ 0.523739] zram: Creating 1 devices ... [ 0.523980] xenoprofile_init: ret 0, events 4, xenoprof_is_primary 0 [ 0.524019] Netfilter messages via NETLINK v0.30. [ 0.524035] nf_conntrack version 0.5.0 (7944 buckets, 31776 max) [ 0.524099] ctnetlink v0.93: registering with nfnetlink. [ 0.524262] ip_tables: (C) 2000-2006 Netfilter Core Team [ 0.524293] TCP: cubic registered [ 0.524298] Initializing XFRM netlink socket [ 0.524346] NET: Registered protocol family 10 [ 0.524486] ip6_tables: (C) 2000-2006 Netfilter Core Team [ 0.524675] sit: IPv6 over IPv4 tunneling driver [ 0.524866] NET: Registered protocol family 17 [ 0.524902] Key type dns_resolver registered [ 0.525076] PM: Hibernation image not present or could not be loaded. [ 0.525094] registered taskstats version 1 [ 0.525121] XENBUS: Device with no driver: device/vkbd/0 [ 0.525127] XENBUS: Device with no driver: device/vfb/0 [ 0.525132] XENBUS: Device with no driver: device/vif/0 [ 0.525191] Magic number: 1:252:3141 [ 0.525898] Freeing unused kernel memory: 716k freed [ 0.526109] Write protecting the kernel read-only data: 8192k [ 0.530939] Freeing unused kernel memory: 172k freed [ 0.531314] Freeing unused kernel memory: 356k freed init started: BusyBox v1.14.3 (2012-06-19 13:33:49 EDT) [ 0.536840] consoletype (1049) used greatest stack depth: 5304 bytes left Mounting directories [ OK ] mount: mount point /proc/bus/usb does not exist [ 0.723241] modprobe (1078) used greatest stack depth: 5064 bytes left mount: mount point /sys/kernel/config does not exist [ 0.731128] core_filesystem (1050) used greatest stack depth: 4984 bytes left [ 0.744953] input: Xen Virtual Keyboard as /devices/virtual/input/input0 [ 0.745268] input: Xen Virtual Pointer as /devices/virtual/input/input1 [ 0.963843] Initialising Xen virtual ethernet driver. [ 1.085463] udevd (1114): /proc/1114/oom_adj is deprecated, please use /proc/1114/oom_score_adj instead.
udevd-work[1125]: error opening ATTR{/sys/devices/system/cpu/cpu0/online} for writing: No such file or directory
Waiting for devices [ OK ]
[ 1.247709] ip (1927) used greatest stack depth: 3768 bytes left
Waiting for init.pre_custom [ OK ] Waiting for fb [ OK ] Starting..[/dev/fb0]/dev/fb0: len:0/dev/fb0: bits/pixel32 (7f69b03c2000): Writting .. [800:600] Done!
.. blah blah
Quoted 3 lines · Konrad Rzeszutek Wilk
I've been getting this when booting a Xen PV guest with 3 CPUs (of which two are online). Any thoughts?
Maybe... I am assuming that your kernel/rcutree.c:1547 is this line of code:
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
This is line 1549 in current mainline.
If my guess is correct, my question is "why on earth is a CPU that has marked itself offline taking a timer interrupt???"
I could provide a patch to make RCU work around this problem from its viewpoint, but taking timer interrupts on an offline CPU is an extremely bad idea. It would be good to fix the underlying problem instead of silencing RCU's warning.
If my guess on what line is warning you is wrong, please do let me know what the line really is -- or even better, the corresponding mainline git commit ID.
Thanx, Paul
Quoted 200 lines
Using config file "/test.xm". Started domain latest (id=6)
[ 0.000000] console [hvc0] enabled, bootconsole disabled [ 0.000000] Xen: using vcpuop timer interface [ 0.000000] installing Xen timer for CPU 0 [ 0.000000] Detected 3093.036 MHz processor. [ 0.000999] Calibrating delay loop (skipped), value calculated using timer frequency.. 6186.07 BogoMIPS (lpj=3093036) [ 0.000999] pid_max: default: 32768 minimum: 301 [ 0.000999] Security Framework initialized [ 0.000999] SELinux: Initializing. [ 0.000999] SELinux: Starting in permissive mode [ 0.000999] Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes) [ 0.000999] Inode-cache hash table entries: 65536 (order: 7, 524288 bytes) [ 0.000999] Mount-cache hash table entries: 256 [ 0.000999] Initializing cgroup subsys cpuacct [ 0.000999] Initializing cgroup subsys freezer [ 0.000999] ENERGY_PERF_BIAS: Set to 'normal', was 'performance' [ 0.000999] ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8) [ 0.000999] CPU: Physical Processor ID: 0 [ 0.000999] CPU: Processor Core ID: 0 [ 0.000999] SMP alternatives: switching to UP code [ 0.026357] cpu 0 spinlock event irq 17 [ 0.026377] Performance Events: unsupported p6 CPU model 42 no PMU driver, software events only. [ 0.026462] NMI watchdog: disabled (cpu0): hardware events not enabled [ 0.026567] installing Xen timer for CPU 1 [ 0.026580] cpu 1 spinlock event irq 24 [ 0.026603] SMP alternatives: switching to SMP code [ 0.049557] NMI watchdog: disabled (cpu1): hardware events not enabled [ 0.049756] installing Xen timer for CPU 2 [ 0.049786] cpu 2 spinlock event irq 31 [ 0.049996] NMI watchdog: disabled (cpu2): hardware events not enabled [ 0.049996] Brought up 3 CPUs [ 0.050313] kworker/u:0 (20) used greatest stack depth: 6000 bytes left [ 0.051028] Grant tables using version 2 layout. [ 0.051065] Grant table initialized [ 0.069993] RTC time: 165:165:165, date: 165/165/65 [ 0.070103] NET: Registered protocol family 16 [ 0.070141] kworker/u:0 (24) used greatest stack depth: 5544 bytes left [ 0.073000] ------------[ cut here ]------------ [ 0.073006] WARNING: at /home/konrad/ssd/linux/kernel/rcutree.c:1547 __rcu_process_callbacks+0x42e/0x440() [ 0.073008] Modules linked in: [ 0.073010] Pid: 12, comm: migration/2 Not tainted 3.5.0-rc2 #2 [ 0.073011] Call Trace: [ 0.073017] <IRQ> [<ffffffff810718ea>] warn_slowpath_common+0x7a/0xb0 [ 0.073019] [<ffffffff81071935>] warn_slowpath_null+0x15/0x20 [ 0.073021] [<ffffffff810edb1e>] __rcu_process_callbacks+0x42e/0x440 [ 0.073023] [<ffffffff810edb50>] rcu_process_callbacks+0x20/0x40 [ 0.073025] [<ffffffff810792c9>] __do_softirq+0xa9/0x160 [ 0.073028] [<ffffffff810a1065>] ? sched_clock_local+0x25/0x90 [ 0.073030] [<ffffffff810d7201>] ? queue_stop_cpus_work+0x51/0xf0 [ 0.073033] [<ffffffff815cee1c>] call_softirq+0x1c/0x30 [ 0.073034] [<ffffffff81039435>] do_softirq+0x65/0xa0 [ 0.073036] [<ffffffff810790c5>] irq_exit+0xd5/0xf0 [ 0.073039] [<ffffffff8132347f>] xen_evtchn_do_upcall+0x2f/0x40 [ 0.073040] [<ffffffff815cee6e>] xen_do_hypervisor_callback+0x1e/0x30 [ 0.073042] <EOI> [<ffffffff810d7201>] ? queue_stop_cpus_work+0x51/0xf0 [ 0.073044] [<ffffffff8100122a>] ? hypercall_page+0x22a/0x1000 [ 0.073045] [<ffffffff8100122a>] ? hypercall_page+0x22a/0x1000 [ 0.073048] [<ffffffff8103361d>] ? xen_force_evtchn_callback+0xd/0x10 [ 0.073049] [<ffffffff81033ed2>] ? check_events+0x12/0x20 [ 0.073051] [<ffffffff81033ebf>] ? xen_restore_fl_direct_reloc+0x4/0x4 [ 0.073053] [<ffffffff810d73aa>] ? stop_machine_cpu_stop+0xba/0xf0 [ 0.073054] [<ffffffff810d72f0>] ? stop_one_cpu_nowait+0x50/0x50 [ 0.073055] [<ffffffff810d7021>] ? cpu_stopper_thread+0xf1/0x1c0 [ 0.073058] [<ffffffff815c5d7e>] ? __schedule+0x3be/0x760 [ 0.073060] [<ffffffff815c6d59>] ? _raw_spin_unlock_irqrestore+0x19/0x30 [ 0.073061] [<ffffffff810d6f30>] ? res_counter_charge+0x10/0x10 [ 0.073064] [<ffffffff81090c46>] ? kthread+0x96/0xa0 [ 0.073065] [<ffffffff815ced24>] ? kernel_thread_helper+0x4/0x10 [ 0.073067] [<ffffffff815c72b8>] ? retint_restore_args+0x5/0x6 [ 0.073069] [<ffffffff815ced20>] ? gs_change+0x13/0x13 [ 0.073073] ---[ end trace 4eaa2a86a8e2da22 ]--- [ 0.073075] dca service started, version 1.12.1 [ 0.074006] PCI: setting up Xen PCI frontend stub [ 0.074015] PCI: pci_cache_line_size set to 64 bytes [ 0.088093] bio: create slab <bio-0> at 0 [ 0.089051] ACPI: Interpreter disabled. [ 0.089063] xen/balloon: Initialising balloon driver. [ 0.091124] xen-balloon: Initialising balloon driver. [ 0.092068] vgaarb: loaded [ 0.092068] usbcore: registered new interface driver usbfs [ 0.092087] usbcore: registered new interface driver hub [ 0.093027] usbcore: registered new device driver usb [ 0.093039] PCI: System does not support PCI [ 0.093039] PCI: System does not support PCI [ 0.094043] NetLabel: Initializing [ 0.094052] NetLabel: domain hash size = 128 [ 0.094057] NetLabel: protocols = UNLABELED CIPSOv4 [ 0.094077] NetLabel: unlabeled traffic allowed by default [ 0.094099] Switching to clocksource xen [ 0.094160] pnp: PnP ACPI: disabled [ 0.101664] NET: Registered protocol family 2 [ 0.101866] IP route cache hash table entries: 32768 (order: 6, 262144 bytes) [ 0.102859] TCP established hash table entries: 131072 (order: 9, 2097152 bytes) [ 0.103661] TCP bind hash table entries: 65536 (order: 8, 1048576 bytes) [ 0.103849] TCP: Hash tables configured (established 131072 bind 65536) [ 0.103858] TCP: reno registered [ 0.103873] UDP hash table entries: 512 (order: 2, 16384 bytes) [ 0.103891] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes) [ 0.104035] NET: Registered protocol family 1 [ 0.104333] RPC: Registered named UNIX socket transport module. [ 0.104347] RPC: Registered udp transport module. [ 0.104356] RPC: Registered tcp transport module. [ 0.104362] RPC: Registered tcp NFSv4.1 backchannel transport module. [ 0.104371] PCI: CLS 0 bytes, default 64 [ 0.104511] Trying to unpack rootfs image as initramfs... [ 0.337888] Freeing initrd memory: 273152k freed [ 0.383239] platform rtc_cmos: registered platform RTC device (no PNP device found) [ 0.383418] Machine check injector initialized [ 0.384702] microcode: CPU0 sig=0x206a7, pf=0x2, revision=0x12 [ 0.384730] microcode: CPU1 sig=0x206a7, pf=0x2, revision=0x12 [ 0.384859] microcode: Microcode Update Driver: v2.00 <[email protected]>, Peter Oruba [ 0.385589] audit: initializing netlink socket (disabled) [ 0.385612] type=2000 audit(1340130254.678:1): initialized [ 0.403267] HugeTLB registered 2 MB page size, pre-allocated 0 pages [ 0.403508] VFS: Disk quotas dquot_6.5.2 [ 0.403552] Dquot-cache hash table entries: 512 (order 0, 4096 bytes) [ 0.403720] NFS: Registering the id_resolver key type [ 0.403739] Key type id_resolver registered [ 0.403882] NTFS driver 2.1.30 [Flags: R/W]. [ 0.403981] msgmni has been set to 1986 [ 0.404021] SELinux: Registering netfilter hooks [ 0.404794] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) [ 0.404806] io scheduler noop registered [ 0.404812] io scheduler deadline registered [ 0.404843] io scheduler cfq registered (default) [ 0.404993] pci_hotplug: PCI Hot Plug PCI Core version: 0.5 [ 0.405260] ioatdma: Intel(R) QuickData Technology Driver 4.00 [ 0.451143] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled [ 0.452662] Non-volatile memory driver v1.3 [ 0.452673] Linux agpgart interface v0.103 [ 0.453294] [drm] Initialized drm 1.1.0 20060810 [ 0.457300] brd: module loaded [ 0.459306] loop: module loaded [ 0.459798] Fixed MDIO Bus: probed [ 0.459807] tun: Universal TUN/TAP device driver, 1.6 [ 0.459813] tun: (C) 1999-2004 Max Krasnyansky <[email protected]> [ 0.459986] ixgbevf: Intel(R) 10 Gigabit PCI Express Virtual Function Network Driver - version 2.6.0-k [ 0.459998] ixgbevf: Copyright (c) 2009 - 2012 Intel Corporation. [ 0.460777] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver [ 0.460788] ehci_hcd: block sizes: qh 112 qtd 96 itd 192 sitd 96 [ 0.460891] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver [ 0.460901] ohci_hcd: block sizes: ed 80 td 96 [ 0.461001] uhci_hcd: USB Universal Host Controller Interface driver [ 0.461293] usbcore: registered new interface driver usblp [ 0.461392] usbcore: registered new interface driver libusual [ 0.461734] i8042: PNP: No PS/2 controller found. Probing ports directly. [ 0.462609] i8042: No controller found [ 0.462737] mousedev: PS/2 mouse device common for all mice [ 0.523312] rtc_cmos rtc_cmos: rtc core: registered rtc_cmos as rtc0 [ 0.523440] rtc_cmos: probe of rtc_cmos failed with error -38 [ 0.523679] EFI Variables Facility v0.08 2004-May-17 [ 0.523734] zram: num_devices not specified. Using default: 1 [ 0.523739] zram: Creating 1 devices ... [ 0.523980] xenoprofile_init: ret 0, events 4, xenoprof_is_primary 0 [ 0.524019] Netfilter messages via NETLINK v0.30. [ 0.524035] nf_conntrack version 0.5.0 (7944 buckets, 31776 max) [ 0.524099] ctnetlink v0.93: registering with nfnetlink. [ 0.524262] ip_tables: (C) 2000-2006 Netfilter Core Team [ 0.524293] TCP: cubic registered [ 0.524298] Initializing XFRM netlink socket [ 0.524346] NET: Registered protocol family 10 [ 0.524486] ip6_tables: (C) 2000-2006 Netfilter Core Team [ 0.524675] sit: IPv6 over IPv4 tunneling driver [ 0.524866] NET: Registered protocol family 17 [ 0.524902] Key type dns_resolver registered [ 0.525076] PM: Hibernation image not present or could not be loaded. [ 0.525094] registered taskstats version 1 [ 0.525121] XENBUS: Device with no driver: device/vkbd/0 [ 0.525127] XENBUS: Device with no driver: device/vfb/0 [ 0.525132] XENBUS: Device with no driver: device/vif/0 [ 0.525191] Magic number: 1:252:3141 [ 0.525898] Freeing unused kernel memory: 716k freed [ 0.526109] Write protecting the kernel read-only data: 8192k [ 0.530939] Freeing unused kernel memory: 172k freed [ 0.531314] Freeing unused kernel memory: 356k freed init started: BusyBox v1.14.3 (2012-06-19 13:33:49 EDT) [ 0.536840] consoletype (1049) used greatest stack depth: 5304 bytes left Mounting directories [ OK ] mount: mount point /proc/bus/usb does not exist [ 0.723241] modprobe (1078) used greatest stack depth: 5064 bytes left mount: mount point /sys/kernel/config does not exist [ 0.731128] core_filesystem (1050) used greatest stack depth: 4984 bytes left [ 0.744953] input: Xen Virtual Keyboard as /devices/virtual/input/input0 [ 0.745268] input: Xen Virtual Pointer as /devices/virtual/input/input1 [ 0.963843] Initialising Xen virtual ethernet driver. [ 1.085463] udevd (1114): /proc/1114/oom_adj is deprecated, please use /proc/1114/oom_score_adj instead.udevd-work[1125]: error opening ATTR{/sys/devices/system/cpu/cpu0/online} for writing: No such file or directory
Waiting for devices [ OK ]
[ 1.247709] ip (1927) used greatest stack depth: 3768 bytes leftWaiting for init.pre_custom [ OK ] Waiting for fb [ OK ] Starting..[/dev/fb0]
/dev/fb0: len:0/dev/fb0: bits/pixel32 (7f69b03c2000): Writting .. [800:600] Done!
.. blah blah
Quoted 11 lines · Paul E. McKenney
Quoted 3 lines · Konrad Rzeszutek Wilk
I've been getting this when booting a Xen PV guest with 3 CPUs (of which two are online). Any thoughts?
Maybe... I am assuming that your
kernel/rcutree.c:1547is this line of code:WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));This is line 1549 in current mainline.
Quoted 7 lines
If my guess is correct, my question is "why on earth is a CPU that has marked itself offline taking a timer interrupt???"
I could provide a patch to make RCU work around this problem from its viewpoint, but taking timer interrupts on an offline CPU is an extremely bad idea. It would be good to fix the underlying problem instead of silencing RCU's warning.
And one possible source for the problem might be if queue_stop_cpus_work() or one of its ancestors in the function-call graph incorrectly enabled interrupts.
Thanx, Paul
Quoted 206 lines
If my guess on what line is warning you is wrong, please do let me know what the line really is -- or even better, the corresponding mainline git commit ID.
Thanx, Paul
Quoted 200 lines
Using config file "/test.xm". Started domain latest (id=6)
[ 0.000000] console [hvc0] enabled, bootconsole disabled [ 0.000000] Xen: using vcpuop timer interface [ 0.000000] installing Xen timer for CPU 0 [ 0.000000] Detected 3093.036 MHz processor. [ 0.000999] Calibrating delay loop (skipped), value calculated using timer frequency.. 6186.07 BogoMIPS (lpj=3093036) [ 0.000999] pid_max: default: 32768 minimum: 301 [ 0.000999] Security Framework initialized [ 0.000999] SELinux: Initializing. [ 0.000999] SELinux: Starting in permissive mode [ 0.000999] Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes) [ 0.000999] Inode-cache hash table entries: 65536 (order: 7, 524288 bytes) [ 0.000999] Mount-cache hash table entries: 256 [ 0.000999] Initializing cgroup subsys cpuacct [ 0.000999] Initializing cgroup subsys freezer [ 0.000999] ENERGY_PERF_BIAS: Set to 'normal', was 'performance' [ 0.000999] ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8) [ 0.000999] CPU: Physical Processor ID: 0 [ 0.000999] CPU: Processor Core ID: 0 [ 0.000999] SMP alternatives: switching to UP code [ 0.026357] cpu 0 spinlock event irq 17 [ 0.026377] Performance Events: unsupported p6 CPU model 42 no PMU driver, software events only. [ 0.026462] NMI watchdog: disabled (cpu0): hardware events not enabled [ 0.026567] installing Xen timer for CPU 1 [ 0.026580] cpu 1 spinlock event irq 24 [ 0.026603] SMP alternatives: switching to SMP code [ 0.049557] NMI watchdog: disabled (cpu1): hardware events not enabled [ 0.049756] installing Xen timer for CPU 2 [ 0.049786] cpu 2 spinlock event irq 31 [ 0.049996] NMI watchdog: disabled (cpu2): hardware events not enabled [ 0.049996] Brought up 3 CPUs [ 0.050313] kworker/u:0 (20) used greatest stack depth: 6000 bytes left [ 0.051028] Grant tables using version 2 layout. [ 0.051065] Grant table initialized [ 0.069993] RTC time: 165:165:165, date: 165/165/65 [ 0.070103] NET: Registered protocol family 16 [ 0.070141] kworker/u:0 (24) used greatest stack depth: 5544 bytes left [ 0.073000] ------------[ cut here ]------------ [ 0.073006] WARNING: at /home/konrad/ssd/linux/kernel/rcutree.c:1547 __rcu_process_callbacks+0x42e/0x440() [ 0.073008] Modules linked in: [ 0.073010] Pid: 12, comm: migration/2 Not tainted 3.5.0-rc2 #2 [ 0.073011] Call Trace: [ 0.073017] <IRQ> [<ffffffff810718ea>] warn_slowpath_common+0x7a/0xb0 [ 0.073019] [<ffffffff81071935>] warn_slowpath_null+0x15/0x20 [ 0.073021] [<ffffffff810edb1e>] __rcu_process_callbacks+0x42e/0x440 [ 0.073023] [<ffffffff810edb50>] rcu_process_callbacks+0x20/0x40 [ 0.073025] [<ffffffff810792c9>] __do_softirq+0xa9/0x160 [ 0.073028] [<ffffffff810a1065>] ? sched_clock_local+0x25/0x90 [ 0.073030] [<ffffffff810d7201>] ? queue_stop_cpus_work+0x51/0xf0 [ 0.073033] [<ffffffff815cee1c>] call_softirq+0x1c/0x30 [ 0.073034] [<ffffffff81039435>] do_softirq+0x65/0xa0 [ 0.073036] [<ffffffff810790c5>] irq_exit+0xd5/0xf0 [ 0.073039] [<ffffffff8132347f>] xen_evtchn_do_upcall+0x2f/0x40 [ 0.073040] [<ffffffff815cee6e>] xen_do_hypervisor_callback+0x1e/0x30 [ 0.073042] <EOI> [<ffffffff810d7201>] ? queue_stop_cpus_work+0x51/0xf0 [ 0.073044] [<ffffffff8100122a>] ? hypercall_page+0x22a/0x1000 [ 0.073045] [<ffffffff8100122a>] ? hypercall_page+0x22a/0x1000 [ 0.073048] [<ffffffff8103361d>] ? xen_force_evtchn_callback+0xd/0x10 [ 0.073049] [<ffffffff81033ed2>] ? check_events+0x12/0x20 [ 0.073051] [<ffffffff81033ebf>] ? xen_restore_fl_direct_reloc+0x4/0x4 [ 0.073053] [<ffffffff810d73aa>] ? stop_machine_cpu_stop+0xba/0xf0 [ 0.073054] [<ffffffff810d72f0>] ? stop_one_cpu_nowait+0x50/0x50 [ 0.073055] [<ffffffff810d7021>] ? cpu_stopper_thread+0xf1/0x1c0 [ 0.073058] [<ffffffff815c5d7e>] ? __schedule+0x3be/0x760 [ 0.073060] [<ffffffff815c6d59>] ? _raw_spin_unlock_irqrestore+0x19/0x30 [ 0.073061] [<ffffffff810d6f30>] ? res_counter_charge+0x10/0x10 [ 0.073064] [<ffffffff81090c46>] ? kthread+0x96/0xa0 [ 0.073065] [<ffffffff815ced24>] ? kernel_thread_helper+0x4/0x10 [ 0.073067] [<ffffffff815c72b8>] ? retint_restore_args+0x5/0x6 [ 0.073069] [<ffffffff815ced20>] ? gs_change+0x13/0x13 [ 0.073073] ---[ end trace 4eaa2a86a8e2da22 ]--- [ 0.073075] dca service started, version 1.12.1 [ 0.074006] PCI: setting up Xen PCI frontend stub [ 0.074015] PCI: pci_cache_line_size set to 64 bytes [ 0.088093] bio: create slab <bio-0> at 0 [ 0.089051] ACPI: Interpreter disabled. [ 0.089063] xen/balloon: Initialising balloon driver. [ 0.091124] xen-balloon: Initialising balloon driver. [ 0.092068] vgaarb: loaded [ 0.092068] usbcore: registered new interface driver usbfs [ 0.092087] usbcore: registered new interface driver hub [ 0.093027] usbcore: registered new device driver usb [ 0.093039] PCI: System does not support PCI [ 0.093039] PCI: System does not support PCI [ 0.094043] NetLabel: Initializing [ 0.094052] NetLabel: domain hash size = 128 [ 0.094057] NetLabel: protocols = UNLABELED CIPSOv4 [ 0.094077] NetLabel: unlabeled traffic allowed by default [ 0.094099] Switching to clocksource xen [ 0.094160] pnp: PnP ACPI: disabled [ 0.101664] NET: Registered protocol family 2 [ 0.101866] IP route cache hash table entries: 32768 (order: 6, 262144 bytes) [ 0.102859] TCP established hash table entries: 131072 (order: 9, 2097152 bytes) [ 0.103661] TCP bind hash table entries: 65536 (order: 8, 1048576 bytes) [ 0.103849] TCP: Hash tables configured (established 131072 bind 65536) [ 0.103858] TCP: reno registered [ 0.103873] UDP hash table entries: 512 (order: 2, 16384 bytes) [ 0.103891] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes) [ 0.104035] NET: Registered protocol family 1 [ 0.104333] RPC: Registered named UNIX socket transport module. [ 0.104347] RPC: Registered udp transport module. [ 0.104356] RPC: Registered tcp transport module. [ 0.104362] RPC: Registered tcp NFSv4.1 backchannel transport module. [ 0.104371] PCI: CLS 0 bytes, default 64 [ 0.104511] Trying to unpack rootfs image as initramfs... [ 0.337888] Freeing initrd memory: 273152k freed [ 0.383239] platform rtc_cmos: registered platform RTC device (no PNP device found) [ 0.383418] Machine check injector initialized [ 0.384702] microcode: CPU0 sig=0x206a7, pf=0x2, revision=0x12 [ 0.384730] microcode: CPU1 sig=0x206a7, pf=0x2, revision=0x12 [ 0.384859] microcode: Microcode Update Driver: v2.00 <[email protected]>, Peter Oruba [ 0.385589] audit: initializing netlink socket (disabled) [ 0.385612] type=2000 audit(1340130254.678:1): initialized [ 0.403267] HugeTLB registered 2 MB page size, pre-allocated 0 pages [ 0.403508] VFS: Disk quotas dquot_6.5.2 [ 0.403552] Dquot-cache hash table entries: 512 (order 0, 4096 bytes) [ 0.403720] NFS: Registering the id_resolver key type [ 0.403739] Key type id_resolver registered [ 0.403882] NTFS driver 2.1.30 [Flags: R/W]. [ 0.403981] msgmni has been set to 1986 [ 0.404021] SELinux: Registering netfilter hooks [ 0.404794] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) [ 0.404806] io scheduler noop registered [ 0.404812] io scheduler deadline registered [ 0.404843] io scheduler cfq registered (default) [ 0.404993] pci_hotplug: PCI Hot Plug PCI Core version: 0.5 [ 0.405260] ioatdma: Intel(R) QuickData Technology Driver 4.00 [ 0.451143] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled [ 0.452662] Non-volatile memory driver v1.3 [ 0.452673] Linux agpgart interface v0.103 [ 0.453294] [drm] Initialized drm 1.1.0 20060810 [ 0.457300] brd: module loaded [ 0.459306] loop: module loaded [ 0.459798] Fixed MDIO Bus: probed [ 0.459807] tun: Universal TUN/TAP device driver, 1.6 [ 0.459813] tun: (C) 1999-2004 Max Krasnyansky <[email protected]> [ 0.459986] ixgbevf: Intel(R) 10 Gigabit PCI Express Virtual Function Network Driver - version 2.6.0-k [ 0.459998] ixgbevf: Copyright (c) 2009 - 2012 Intel Corporation. [ 0.460777] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver [ 0.460788] ehci_hcd: block sizes: qh 112 qtd 96 itd 192 sitd 96 [ 0.460891] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver [ 0.460901] ohci_hcd: block sizes: ed 80 td 96 [ 0.461001] uhci_hcd: USB Universal Host Controller Interface driver [ 0.461293] usbcore: registered new interface driver usblp [ 0.461392] usbcore: registered new interface driver libusual [ 0.461734] i8042: PNP: No PS/2 controller found. Probing ports directly. [ 0.462609] i8042: No controller found [ 0.462737] mousedev: PS/2 mouse device common for all mice [ 0.523312] rtc_cmos rtc_cmos: rtc core: registered rtc_cmos as rtc0 [ 0.523440] rtc_cmos: probe of rtc_cmos failed with error -38 [ 0.523679] EFI Variables Facility v0.08 2004-May-17 [ 0.523734] zram: num_devices not specified. Using default: 1 [ 0.523739] zram: Creating 1 devices ... [ 0.523980] xenoprofile_init: ret 0, events 4, xenoprof_is_primary 0 [ 0.524019] Netfilter messages via NETLINK v0.30. [ 0.524035] nf_conntrack version 0.5.0 (7944 buckets, 31776 max) [ 0.524099] ctnetlink v0.93: registering with nfnetlink. [ 0.524262] ip_tables: (C) 2000-2006 Netfilter Core Team [ 0.524293] TCP: cubic registered [ 0.524298] Initializing XFRM netlink socket [ 0.524346] NET: Registered protocol family 10 [ 0.524486] ip6_tables: (C) 2000-2006 Netfilter Core Team [ 0.524675] sit: IPv6 over IPv4 tunneling driver [ 0.524866] NET: Registered protocol family 17 [ 0.524902] Key type dns_resolver registered [ 0.525076] PM: Hibernation image not present or could not be loaded. [ 0.525094] registered taskstats version 1 [ 0.525121] XENBUS: Device with no driver: device/vkbd/0 [ 0.525127] XENBUS: Device with no driver: device/vfb/0 [ 0.525132] XENBUS: Device with no driver: device/vif/0 [ 0.525191] Magic number: 1:252:3141 [ 0.525898] Freeing unused kernel memory: 716k freed [ 0.526109] Write protecting the kernel read-only data: 8192k [ 0.530939] Freeing unused kernel memory: 172k freed [ 0.531314] Freeing unused kernel memory: 356k freed init started: BusyBox v1.14.3 (2012-06-19 13:33:49 EDT) [ 0.536840] consoletype (1049) used greatest stack depth: 5304 bytes left Mounting directories [ OK ] mount: mount point /proc/bus/usb does not exist [ 0.723241] modprobe (1078) used greatest stack depth: 5064 bytes left mount: mount point /sys/kernel/config does not exist [ 0.731128] core_filesystem (1050) used greatest stack depth: 4984 bytes left [ 0.744953] input: Xen Virtual Keyboard as /devices/virtual/input/input0 [ 0.745268] input: Xen Virtual Pointer as /devices/virtual/input/input1 [ 0.963843] Initialising Xen virtual ethernet driver. [ 1.085463] udevd (1114): /proc/1114/oom_adj is deprecated, please use /proc/1114/oom_score_adj instead.udevd-work[1125]: error opening ATTR{/sys/devices/system/cpu/cpu0/online} for writing: No such file or directory
Waiting for devices [ OK ]
[ 1.247709] ip (1927) used greatest stack depth: 3768 bytes leftWaiting for init.pre_custom [ OK ] Waiting for fb [ OK ] Starting..[/dev/fb0]
/dev/fb0: len:0/dev/fb0: bits/pixel32 (7f69b03c2000): Writting .. [800:600] Done!
.. blah blah
Quoted 10 lines · Paul E. McKenney
Quoted 3 lines · Konrad Rzeszutek Wilk
I've been getting this when booting a Xen PV guest with 3 CPUs (of which two are online). Any thoughts?
Maybe... I am assuming that your
kernel/rcutree.c:1547is this line of code:WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));This is line 1549 in current mainline.
<nods>
[ 0.064998] ------------[ cut here ]------------^M [ 0.065004] WARNING: at /home/konrad/linux-linus/kernel/rcutree.c:1549 __rcu_process_callbacks+0x42e/0x440()^M [ 0.065005] Modules linked in:^M [ 0.065006] Pid: 12, comm: migration/2 Not tainted 3.5.0-rc3upstream-00111-gf40759e #1^M [ 0.065007] Call Trace:^M [ 0.065011] <IRQ> [<ffffffff810718ba>] warn_slowpath_common+0x7a/0xb0^M [ 0.065013] [<ffffffff81071905>] warn_slowpath_null+0x15/0x20^M [ 0.065022] [<ffffffff810edb7e>] __rcu_process_callbacks+0x42e/0x440^M [ 0.065026] [<ffffffff810edbb0>] rcu_process_callbacks+0x20/0x40^M [ 0.065029] [<ffffffff81079299>] __do_softirq+0xa9/0x160^M [ 0.065033] [<ffffffff810a1035>] ? sched_clock_local+0x25/0x90^M [ 0.065037] [<ffffffff810d7201>] ? queue_stop_cpus_work+0x61/0xf0^M [ 0.065042] [<ffffffff815c44dc>] call_softirq+0x1c/0x30^M [ 0.065044] [<ffffffff81039435>] do_softirq+0x65/0xa0^M [ 0.065047] [<ffffffff81079095>] irq_exit+0xd5/0xf0^M [ 0.065050] [<ffffffff81322f2f>] xen_evtchn_do_upcall+0x2f/0x40^M [ 0.065054] [<ffffffff815c452e>] xen_do_hypervisor_callback+0x1e/0x30^M [ 0.065058] <EOI> [<ffffffff810d7201>] ? queue_stop_cpus_work+0x61/0xf0^M
Quoted 3 lines
If my guess is correct, my question is "why on earth is a CPU that has marked itself offline taking a timer interrupt???"
So.. part of this is that I think the CPU hotplug code is a bit brain-dead.
In the Xen side, when a guest starts - it boots all the available CPUs (in this case three), and then it brings down the one it doesn't need. How many it brings down is dependent on two simple lines in the guest config:
vcpus=2
maxvcpus=3
The "offline" CPU can be immediately brought back and its parked in the cpu_idle call. Which looking at it - means that it also hits the schedule_bug when it gets to be onlined. Grrrr..
But irregardless of that - when a CPU is brought down it does call the CPU offline notifiers - and I am not sure why the RCU isn't notified? Could it be a race perhaps?
Quoted 4 lines
I could provide a patch to make RCU work around this problem from its viewpoint, but taking timer interrupts on an offline CPU is an extremely bad idea. It would be good to fix the underlying problem instead of
Right.
Quoted 1 line
silencing RCU's warning.
Of course.
Quoted 4 lines
If my guess on what line is warning you is wrong, please do let me know what the line really is -- or even better, the corresponding mainline git commit ID.
This is f40759e but I think earlier versions of v3.5 exhibited this too.
Quoted 13 lines · Konrad Rzeszutek Wilk
Quoted 10 lines · Paul E. McKenney
Quoted 3 lines · Konrad Rzeszutek Wilk
I've been getting this when booting a Xen PV guest with 3 CPUs (of which two are online). Any thoughts?
Maybe... I am assuming that your
kernel/rcutree.c:1547is this line of code:WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));This is line 1549 in current mainline.
<nods>
Quoted 15 lines
[ 0.064998] ------------[ cut here ]------------^M [ 0.065004] WARNING: at /home/konrad/linux-linus/kernel/rcutree.c:1549 __rcu_process_callbacks+0x42e/0x440()^M [ 0.065005] Modules linked in:^M [ 0.065006] Pid: 12, comm: migration/2 Not tainted 3.5.0-rc3upstream-00111-gf40759e #1^M [ 0.065007] Call Trace:^M [ 0.065011] <IRQ> [<ffffffff810718ba>] warn_slowpath_common+0x7a/0xb0^M [ 0.065013] [<ffffffff81071905>] warn_slowpath_null+0x15/0x20^M [ 0.065022] [<ffffffff810edb7e>] __rcu_process_callbacks+0x42e/0x440^M [ 0.065026] [<ffffffff810edbb0>] rcu_process_callbacks+0x20/0x40^M [ 0.065029] [<ffffffff81079299>] __do_softirq+0xa9/0x160^M [ 0.065033] [<ffffffff810a1035>] ? sched_clock_local+0x25/0x90^M [ 0.065037] [<ffffffff810d7201>] ? queue_stop_cpus_work+0x61/0xf0^M [ 0.065042] [<ffffffff815c44dc>] call_softirq+0x1c/0x30^M [ 0.065044] [<ffffffff81039435>] do_softirq+0x65/0xa0^M [ 0.065047] [<ffffffff81079095>] irq_exit+0xd5/0xf0^M
Here is the interrupt. Why are we taking an interrupt on an offline CPU? This is very very bad.
Quoted 18 lines
[ 0.065050] [<ffffffff81322f2f>] xen_evtchn_do_upcall+0x2f/0x40^M [ 0.065054] [<ffffffff815c452e>] xen_do_hypervisor_callback+0x1e/0x30^M [ 0.065058] <EOI> [<ffffffff810d7201>] ? queue_stop_cpus_work+0x61/0xf0^MQuoted 3 lines
If my guess is correct, my question is "why on earth is a CPU that has marked itself offline taking a timer interrupt???"
So.. part of this is that I think the CPU hotplug code is a bit brain-dead.
In the Xen side, when a guest starts - it boots all the available CPUs (in this case three), and then it brings down the one it doesn't need. How many it brings down is dependent on two simple lines in the guest config:
vcpus=2
maxvcpus=3
Quoted 7 lines
The "offline" CPU can be immediately brought back and its parked in the
cpu_idlecall. Which looking at it - means that it also hits theschedule_bugwhen it gets to be onlined. Grrrr..But irregardless of that - when a CPU is brought down it does call the CPU offline notifiers - and I am not sure why the RCU isn't notified? Could it be a race perhaps?
RCU -is- being notified of the CPU going down, as near as I can tell.
As noted previously, the real question is "Why on earth is an offline CPU taking an interrupt???" RCU is complaining that it is being asked to do work while running on an offline CPU.
So, where is that interrupt coming from? It needs to not be happening.
Thanx, Paul
Quoted 20 lines
Quoted 3 lines
I could provide a patch to make RCU work around this problem from its viewpoint, but taking timer interrupts on an offline CPU is an extremely bad idea. It would be good to fix the underlying problem instead of
Right.
Quoted 1 line
silencing RCU's warning.
Of course.
Quoted 4 lines
If my guess on what line is warning you is wrong, please do let me know what the line really is -- or even better, the corresponding mainline git commit ID.
This is f40759e but I think earlier versions of v3.5 exhibited this too. --
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