[PATCH RESEND v4] powerpc: kvm: fix rare but potential deadlock scene

[Alexander Graf]

On 19.11.2013, at 07:12, Liu Ping Fan <kernelfans at gmail.com> 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 at linux.vnet.ibm.com>

Any particular reason for the resend? The patch is already applied, no?


Alex