Re: WARNING: at arch/x86/kernel/kvmclock.c:127

[Eric B Munson <emunson@mgebm.net>]

On Tue, 5 Jun 2012 20:20:59 +0200, Frank Arnold wrote:
> Hi all,
>
> I observed the following warning during testing of 3.5-rc1, involving
> some intensive and random CPU online state toggling through sysfs. It
> only shows up about 1 out of 500 times. Also, there was no KVM guest
> running on the system.
>

This warning kicks off if the watchdog_timer_fn function is called 
outside of an
atomic context, the warning itself is not re

> ------------[ cut here ]------------
> WARNING: at arch/x86/kernel/kvmclock.c:127
> kvm_check_and_clear_guest_paused+0x52/0x60()
> Hardware name: Dinar
> Modules linked in: nfs lockd fscache auth_rpcgss nfs_acl sunrpc ipv6
> ext4 jbd2 dm_mod powernow_k8 freq_table mperf kvm_amd kvm 
> crc32c_intel
> ghash_clmulni_intel aesni_intel cryptd aes_x86_64 aes_generic 
> microcode
> serio_raw pcspkr k10temp amd64_edac_mod edac_core edac_mce_amd 
> i2c_piix4
> sg bnx2 ext3 jbd mbcache sr_mod cdrom sd_mod crc_t10dif ata_generic
> pata_acpi pata_atiixp ahci libahci usb_storage radeon ttm 
> drm_kms_helper
> drm i2c_algo_bit i2c_core [last unloaded: scsi_wait_scan]
> Pid: 3593, comm: py_topology Not tainted 3.5.0-rc1+ #1
> Call Trace:
>  [<ffffffff8104fd7f>] warn_slowpath_common+0x7f/0xc0
>  [<ffffffff8104fdda>] warn_slowpath_null+0x1a/0x20
>  [<ffffffff8103f252>] kvm_check_and_clear_guest_paused+0x52/0x60
>  [<ffffffff810d29f7>] watchdog_timer_fn+0x97/0x1b0
>  [<ffffffff81077743>] __run_hrtimer+0x83/0x1d0
>  [<ffffffff810d2960>] ? touch_softlockup_watchdog_sync+0x40/0x40
>  [<ffffffff81077b26>] hrtimer_interrupt+0x106/0x240
>  [<ffffffff81077d98>] migrate_hrtimers+0x138/0x1a0
>  [<ffffffff8150eb76>] hrtimer_cpu_notify+0xe4/0xeb
>  [<ffffffff8151a655>] notifier_call_chain+0x55/0x80
>  [<ffffffff8107961e>] __raw_notifier_call_chain+0xe/0x10
>  [<ffffffff81052e50>] __cpu_notify+0x20/0x40
>  [<ffffffff81052e85>] cpu_notify_nofail+0x15/0x30
>  [<ffffffff814fc6bd>] _cpu_down+0x12d/0x270
>  [<ffffffff814fc836>] cpu_down+0x36/0x50
>  [<ffffffff814feeb4>] store_online+0x74/0xd0
>  [<ffffffff8133e8a0>] dev_attr_store+0x20/0x30
>  [<ffffffff811e0d5f>] sysfs_write_file+0xef/0x170
>  [<ffffffff81171708>] vfs_write+0xc8/0x190
>  [<ffffffff811718d1>] sys_write+0x51/0x90
>  [<ffffffff8151eba9>] system_call_fastpath+0x16/0x1b
> ---[ end trace 574db9e069f4f35e ]---
>
> This is a regression introduced by the following commit:
>
> commit 3b5d56b9317fa7b5407dff1aa7b115bf6cdbd494
> Author: Eric B Munson <emunson@mgebm.net>
> Date:   Sat Mar 10 14:37:26 2012 -0500
>
>     kvmclock: Add functions to check if the host has stopped the vm
>
>     When a host stops or suspends a VM it will set a flag to show 
> this.  The
>     watchdog will use these functions to determine if a softlockup is
> real, or the
>     result of a suspended VM.
>
>     Signed-off-by: Eric B Munson <emunson@mgebm.net>
>     asm-generic changes Acked-by: Arnd Bergmann <arnd@arndb.de>
>     Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>     Signed-off-by: Avi Kivity <avi@redhat.com>