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Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH] block: fix bdrv_ioctl called from coroutine |
Date: |
Fri, 18 Dec 2015 09:17:16 +0800 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, 12/17 13:51, Paolo Bonzini wrote:
>
>
> 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.
>
Looking at bdrv_flush again I see what you mean. Thanks for explaining!
Reviewed-by: Fam Zheng <address@hidden>