linux-kernel - Re: WARNING: kernel/smp.c:292 smp_call_function_single [Was: mmotm 2009-11-24-16-47 uploaded]

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Date:	Fri, 27 Nov 2009 16:17:16 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mm-commits@...r.kernel.org, Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	the arch/x86 maintainers <x86@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: WARNING: kernel/smp.c:292 smp_call_function_single [Was: mmotm
 2009-11-24-16-47 uploaded]

On Fri, 2009-11-27 at 16:03 +0100, Jiri Slaby wrote:
> On 11/25/2009 01:47 AM, akpm@...ux-foundation.org wrote:
> > The mm-of-the-moment snapshot 2009-11-24-16-47 has been uploaded to
> 
> Hi, when executing qemu-kvm I often get following warning and a hard lockup.
> 
> WARNING: at kernel/smp.c:292 smp_call_function_single+0xbd/0x140()
> Hardware name: To Be Filled By O.E.M.
> Modules linked in: kvm_intel kvm fuse ath5k ath
> Pid: 3265, comm: qemu-kvm Not tainted 2.6.32-rc8-mm1_64 #912
> Call Trace:
>  [<ffffffff81039678>] warn_slowpath_common+0x78/0xb0
>  [<ffffffffa007fd50>] ? __vcpu_clear+0x0/0xd0 [kvm_intel]
>  [<ffffffff810396bf>] warn_slowpath_null+0xf/0x20
>  [<ffffffff8106410d>] smp_call_function_single+0xbd/0x140
>  [<ffffffffa0080af6>] vmx_vcpu_load+0x46/0x170 [kvm_intel]
>  [<ffffffffa004dd94>] kvm_arch_vcpu_load+0x24/0x60 [kvm]
>  [<ffffffffa0047a8d>] kvm_sched_in+0xd/0x10 [kvm]
>  [<ffffffff8102de37>] finish_task_switch+0x67/0xc0
>  [<ffffffff814699f8>] schedule+0x2f8/0x9c0

> 
> It is a regression against 2009-11-13-19-59.
> 
> Any ideas?

Looks like kvm is trying to send an IPI from the preempt notifiers,
which are called with IRQs disabled, not a sane thing to do.

If they really want that, they'll have to use a pre-allocated struct
call_single_data and use __smp_call_function_single.

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