From: Paul Mackerras <paulus@samba.org>
To: Liu Ping Fan <qemulist@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, Alexander Graf <agraf@suse.de>,
kvm-ppc@vger.kernel.org
Subject: Re: [PATCH v4] powerpc: kvm: fix rare but potential deadlock scene
Date: Sat, 16 Nov 2013 17:55:17 +1100 [thread overview]
Message-ID: <20131116065517.GA18339@iris.ozlabs.ibm.com> (raw)
In-Reply-To: <1384504501-19348-1-git-send-email-pingfank@linux.vnet.ibm.com>
On Fri, Nov 15, 2013 at 04:35:00PM +0800, Liu Ping Fan wrote:
> Since kvmppc_hv_find_lock_hpte() is called from both virtmode and
> realmode, so it can trigger the deadlock.
>
> Suppose the following scene:
>
> Two physical cpuM, cpuN, two VM instances A, B, each VM has a group of
> vcpus.
>
> If on cpuM, vcpu_A_1 holds bitlock X (HPTE_V_HVLOCK), then is switched
> out, and on cpuN, vcpu_A_2 try to lock X in realmode, then cpuN will be
> caught in realmode for a long time.
>
> What makes things even worse if the following happens,
> On cpuM, bitlockX is hold, on cpuN, Y is hold.
> vcpu_B_2 try to lock Y on cpuM in realmode
> vcpu_A_2 try to lock X on cpuN in realmode
>
> Oops! deadlock happens
>
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
Reviewed-by: Paul Mackerras <paulus@samba.org>
next prev parent reply other threads:[~2013-11-16 6:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-15 8:35 [PATCH v4] powerpc: kvm: fix rare but potential deadlock scene Liu Ping Fan
2013-11-15 8:35 ` [PATCH v2] powerpc: kvm: optimize "sc 1" as fast return Liu Ping Fan
2013-11-16 7:00 ` Paul Mackerras
2013-11-18 1:06 ` liu ping fan
2013-11-16 6:55 ` Paul Mackerras [this message]
2013-11-18 21:32 ` [PATCH v4] powerpc: kvm: fix rare but potential deadlock scene Alexander Graf
2013-11-18 21:43 ` Alexander Graf
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