linux-kernel - Re: [PATCH] KVM: X86: Fix softlockup when get the current kvmclock timestamp

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Date:   Mon, 6 Nov 2017 10:29:40 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH] KVM: X86: Fix softlockup when get the current kvmclock
 timestamp

On 06/11/2017 01:55, Wanpeng Li wrote:
> This can be reproduced when running kvm-unit-tests/hyperv_stimer.flat and 
> cpu-hotplug stress simultaneously. kvm_get_time_scale() takes too long which 
> results in softlockup.

Apart from the pr_debug, kvm_get_time_scale should take less than a
microsecond.  The patch is fine, but can you confirm that pr_debug is
the culprit?

Thanks,

Paolo