linux-kernel - Re: CPU softlockup due to smp_call

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Date:	Thu, 5 Apr 2012 10:25:39 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Milton Miller <miltonm@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Avi Kivity <avi@...hat.com>, Dave Jones <davej@...hat.com>,
	kvm@...r.kernel.org,
	"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: CPU softlockup due to smp_call_function()

On Thu, Apr 5, 2012 at 6:06 AM, Milton Miller <miltonm@....com> wrote:
>
> On Wed, 4 Apr 2012 about 22:12:36 +0200, Sasha Levin wrote:
>> I've starting seeing soft lockups resulting from smp_call_function()
>> calls. I've attached two different backtraces of this happening with
>> different code paths.
>>
>> This is running inside a KVM guest with the trinity fuzzer, using
>> today's linux-next kernel.
>
> Hi Sasha.
>
> You have two different call sites (arch/x86/mm/pageattr.c
> cpa_flush_range and net/core/dev.c netdev_run_todo), and both use
> call on_each_cpu with wait=1.
>
> I tried a few options but can't get close enough to your compiled
> length of 2a0 to know if the code is spinning on the first
> csd_lock_wait in csd_lock or in the second csd_lock_wait after the
> call to arch_send_call_function_ipi_mask (aka smp_ops + 0x44 in my
> x86_64 compile).  Please check your disassembly and report.

Hi Milton,

# addr2line -i -e /usr/src/linux/vmlinux ffffffff8111f30e
/usr/src/linux/kernel/smp.c:102
/usr/src/linux/kernel/smp.c:554

So It's the 2nd lock.

I'll work on adding the debug code mentioned in your mail.
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