linux-kernel - Re: [kvm.git & 2.6.37-rc1] KVM deadlock with CONFIG

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Date:	Tue, 09 Nov 2010 12:38:19 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>
CC:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	kvm <kvm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [kvm.git & 2.6.37-rc1] KVM deadlock with CONFIG_PREEMPT host

On 11/08/2010 12:28 PM, Jan Kiszka wrote:
> Am 08.11.2010 10:18, Markus Trippelsdorf wrote:
> >  On Mon, Nov 08, 2010 at 10:04:00AM +0100, Jan Kiszka wrote:
> >>  Hi,
> >>
> >>  I'm seeing lock-ups of the QEMU process on kvm.git as well as current
> >>  upstream kernels. This is a backtrace of the hanging VCPU thread:
> >>
> >>  [<ffffffff810a27bc>] __stop_cpus+0x184/0x1a7
> >>  [<ffffffff810a286f>] try_stop_cpus+0x40/0x59
> >>  [<ffffffff8103a30c>] synchronize_sched_expedited+0x84/0x9d
> >>  [<ffffffff810715a3>] __synchronize_srcu+0x33/0x72
> >>  [<ffffffff810715f7>] synchronize_srcu_expedited+0x15/0x17
> >>  [<ffffffffa06602ae>] __kvm_set_memory_region+0x6a3/0x782 [kvm]
> >>  [<ffffffffa06603c4>] kvm_set_memory_region+0x37/0x50 [kvm]
> >>  [<ffffffffa0661c30>] kvm_vm_ioctl_set_memory_region+0x18/0x1a [kvm]
> >>  [<ffffffffa0661e5f>] kvm_vm_ioctl+0x22d/0x3b1 [kvm]
> >>  [<ffffffff81143c26>] do_vfs_ioctl+0x5a1/0x5e2
> >>  [<ffffffff81143cbd>] sys_ioctl+0x56/0x79
> >>  [<ffffffff81002df2>] system_call_fastpath+0x16/0x1b
> >>  [<ffffffffffffffff>] 0xffffffffffffffff
> >>
> >>  This issue disappears when disabling CONFIG_PREEMPT on the host.
> >>  According to some rough bisecting, it was imported into kvm.git with
> >>  merge 146d3bb06b. Given that RCU is involved, I also tried
> >>  force-enabling non-preemptible CONFIG_TREE_RCU again, but that made no
> >>  difference as long as PREEMPT is on.
> >>
> >>  Can anyone confirm this or does someone have an idea what goes wrong? Of
> >>  course, .config will be provided if required.
> >
> >  This patch should help (,it fixes the problem in my case):
> >  http://article.gmane.org/gmane.linux.kernel/1058018
>
> Yeah, that works here as well.
>
> Would be a nice-to-have in kvm.git until it's pull via the next upstream
> merge. At least for me this bug triggers at every VM boot.
>

I just did so.  Testing with CONFIG_PREEMPT is important.

-- 
error compiling committee.c: too many arguments to function

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