Re: [Qemu-block] [Questions] NBD issue or CoMutex->holder issue?

[Changlong Xie]

On 10/11/2016 06:47 PM, Paolo Bonzini wrote:
> > the free_sema->queue head, so set free_sema->holder as
> > >revelant coroutine.
> NBD is using the CoMutex in a way that wasn't anticipated.  The simplest
> fix is to change it to CoQueue, which is like a condition variable.
> Instead of locking if in_flight >= MAX_NBD_REQUESTS - 1, wait on the
> queue while in_flight == MAX_NBD_REQUESTS.  Instead of unlocking, use
> qemu_co_queue_next to wake up one request.

Thanks for your explanation! will send out a patch later.


Thanks
        -Xie

> Thanks for the report!
>
> Paolo
>
> > >For example if there are N(N=26 and MAX_NBD_REQUESTS=16) nbd write
> > >requests, so we'll invoke nbd_client_co_pwritev 26 times.
> > >time     request No   Actions
> > >1         1           in_flight=1, Coroutine=C1
> > >2         2           in_flight=2, Coroutine=C2