Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine

[Paolo Bonzini <pbonzini@redhat.com>]

On 17/12/2015 13:33, Fam Zheng wrote:
> > In the coroutine case, the yield is hidden in the drivers, and it may or
> > may not happen.  For example, qcow2_co_flush_to_os starts with
> > 
> >     qemu_co_mutex_lock(&s->lock);
> > 
> > which can yield.
> 
> bdrv_ioctl, on the contrary, is emulated with .bdrv_aio_ioctl, so it always
> yields (unless -ENOTSUP), that's why I think aio_poll() is necessary in both
> branches.

But why should it yield, if called in coroutine context?  bdrv_flush
doesn't yield if emulated with .bdrv_aio_flush *and* called in coroutine
context.  bdrv_ioctl should do the same, I think.

Paolo