Re: [Qemu-devel] Re: qemu-kvm hangs if multipath device is queing

[Peter Lieven]

Am 19.05.2010 um 10:18 schrieb Peter Lieven:

> Kevin Wolf wrote:
>> Am 19.05.2010 09:29, schrieb Christoph Hellwig:
>>  
>>> On Tue, May 18, 2010 at 03:22:36PM +0200, Kevin Wolf wrote:
>>>    
>>>> I think it's stuck here in an endless loop:
>>>> 
>>>>    while (laiocb->ret == -EINPROGRESS)
>>>>        qemu_laio_completion_cb(laiocb->ctx);
>>>> 
>>>> Can you verify this by single-stepping one or two loop iterations? ret
>>>> and errno after the read call could be interesting, too.
>>>>      
>>> Maybe the compiler is just too smart.  Without some form of barrier
>>> it could just optimize the loop away as laiocb->ret couldn't change
>>> in a normal single-threaded environment.
>>>    
>> 
>> It probably could in theory, but in practice we're in a read() inside
>> qemu_laio_completion, so it didn't do it here.
>>  
> if you supply a patch that will add some usleeps at the point in
> question i'm willing to test if it solves the 100% cpu problem.

can someone help here? what would be the best option to add some
usleeps?

>> Kevin
>> 
>>  
> 
> 
>