Re: [Xen-devel] Re: A race condition introduced by changeset 15175: Re-init hypercall stubs page after HVM save/restore

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 21/10/08 04:38, "Mukesh" <mukesh.rathor@xxxxxxxxxx> wrote:

>> Hi Dexuan,
>> 
>> Are you really sure that this is the problem? The suspend_lock was
>> introduced specifically to solve this problem. Note that the BSP takes this
>> lock before messing with the hypercall page.
>> 
>>  -- Keir
> 
> I'm also looking at this now (I'm on 3.1.4 BTW). I see both hang and panic. it
> appears I see the hang because the "master" vcpu is trying to catch other
> vcpus
> right at the cpu_relax so it can grab the lock in write mode. With many VCPUs
> it's just not happening..... Not sure i like the design of this very much...
> i'm
> gonna try to modify it a bit ....

Hmmm, yes, agreed. We need a completely different approach, or a lock which
doesn't allow in more readers when there is a waiting writer. I'll look into
it.

 -- Keir



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