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Date: Thu, 08 Jan 2015 19:12:07 +0100
From: Gerhard Wiesinger <lists@wiesinger.com>
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Subject: Re: [Qemu-devel] Fedora FC21 - Bug: 100% CPU and hangs in
 gettimeofday(&tp, NULL); forever
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To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org

On 08.01.2015 18:24, Paolo Bonzini wrote:
>
> On 08/01/2015 14:36, Gerhard Wiesinger wrote:
>> Quitting and reattaching gdb also hangs here, so gettimeofday takes 100%
>> CPU and never ends!
>>
>> Therefore I guess this is a problem either in the Linux kernel or in
>> QEMU/KVM.
> What kernel are you running on (and were you running on)?
>
> Can you try F20 host and F21 guest or vice versa?

Hello Paolo,

Always latest available stable versions (kernel/qemu-kvm):
F20: 3.17.6-200.fc20.x86_64 on guest/host, qemu-kvm-1.6.2-10.fc20.x86_64 
on host
F21: 3.17.7-300.fc21.x86_64 on guest/host, qemu-kvm-2.1.2-7.fc21.x86_64 
on host
(I had also 3.17.6-300.fc21.x86_64 and it happended there, too).

The topic is: it happens after some time (e.g. hours to days)
It is production environment running around 10VMs and I want to avoid 
many experiments there. Since kernels were the same on FC20/F21 and 
qemu/kvm changed from 1.6.2 to 2.1.2 I guess the topic seems to be 
there. Also newer gcc might be a topic.

https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/kernel/time/timekeeping.c?id=refs/tags/v3.17.7#n695
I guess it hangs in the do/while loop here:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/kernel/time/timekeeping.c?id=refs/tags/v3.17.7#n493

Ciao,
Gerhard