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Date: Fri, 14 Nov 2014 13:54:49 -0800
Message-ID: <CAHTgTXVVN7wFdD5eJXs-gpoiEHrqcpeEx39Yetru1Mbvo0enWg@mail.gmail.com>
Subject: Re: x86 math_error warning in Linux kernel 3.10
From: Vinson Lee <vlee@twopensource.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@suse.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Fenghua Yu <fenghua.yu@intel.com>,
        Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
        Suresh Siddha <sbsiddha@gmail.com>,
        Matt Fleming <matt.fleming@intel.com>, Oleg Nesterov <oleg@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Nov 14, 2014 at 12:39 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Fri, 14 Nov 2014, Borislav Petkov wrote:
>> On Fri, Nov 14, 2014 at 12:19:16PM -0800, Vinson Lee wrote:
>> > Hi.
>> >
>> > We hit this x86 math_error warning in Linux kernel 3.10.
>> >
>> > ------------[ cut here ]------------
>> > WARNING: at arch/x86/include/asm/fpu-internal.h:524 math_error+0xd1/0x219()
>> > Modules linked in: cls_basic act_mirred cls_u32 veth sch_ingress
>> > netconsole configfs ipv6 dm_multipath scsi_dh video sbs sbshc hed
>> > acpi_pad acpi_ipmi acpi_i2c parport_pc lp parport tcp_diag inet_diag
>> > ipmi_si ipmi_devintf ipmi_msghandler dell_rbu sg iTCO_wdt
>> > iTCO_vendor_support dcdbas igb i2c_algo_bit ptp pps_core shpchp
>> > lpc_ich i2c_i801 mfd_core i2c_core ioatdma dca i7core_edac edac_core
>> > microcode freq_table mperf ahci libahci libata sd_mod scsi_mod
>> > CPU: 2 PID: 53182 Comm: java Not tainted 3.10.50 #1
>> >  0000000000000000 ffff8808e1f5be38 ffffffff8146cb74 ffff8808e1f5be70
>> >  ffffffff8103cbf9 0000000000000000 ffff88090b2c9730 ffff8808e1f5bf58
>> >  0000000000000010 0000000000000000 ffff8808e1f5be80 ffffffff8103ccbf
>> > Call Trace:
>> >  [<ffffffff8146cb74>] dump_stack+0x19/0x1b
>> >  [<ffffffff8103cbf9>] warn_slowpath_common+0x65/0x7d
>> >  [<ffffffff8103ccbf>] warn_slowpath_null+0x1a/0x1c
>> >  [<ffffffff8100317b>] math_error+0xd1/0x219
>> >  [<ffffffff81007f6c>] ? read_tsc+0x9/0x19
>> >  [<ffffffff8107bab8>] ? timekeeping_get_ns.constprop.10+0x11/0x36
>> >  [<ffffffff8107bf32>] ? ktime_get+0x68/0x76
>> >  [<ffffffff81007f6c>] ? read_tsc+0x9/0x19
>> >  [<ffffffff8107bab8>] ? timekeeping_get_ns.constprop.10+0x11/0x36
>> >  [<ffffffff810032d6>] do_coprocessor_error+0x13/0x15
>> >  [<ffffffff81478a38>] coprocessor_error+0x18/0x20
>> > ---[ end trace 3e4a6532a67ba6d3 ]---
>>
>> AFAICT, you're getting an FPU exception for a task which hasn't used the
>> FPU or current is somehow pointing to the wrong task.
>>
>> Can you trigger this with the latest kernel too, i.e., say, 3.18-rc4?
>
> Also Vinson forgot to mention HOW that is triggered. Without an
> explanation of the reproducer it's hard to tell what's going wrong.
>
> Thanks,
>
>         tglx


Thanks for the quick responses. This is an infrequent warning. We have
yet to reliably reproduce it or narrow down to a test case.

Thanks.
Vinson
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