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Date: Fri, 30 Mar 2012 11:25:24 +0100
Message-ID: <CAJSP0QV52+JJXzBK+01JQOmZcm1n0eRsusUBMeApmBbirM4sYQ@mail.gmail.com>
From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] block: fix streaming/closing race
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@linux.vnet.ibm.com

On Fri, Mar 30, 2012 at 9:31 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 30/03/2012 09:19, Stefan Hajnoczi ha scritto:
>>> > +void block_job_cancel_sync(BlockJob *job)
>>> > +{
>>> > + =A0 =A0BlockDriverState *bs =3D job->bs;
>>> > +
>>> > + =A0 =A0assert(bs->job =3D=3D job);
>>> > + =A0 =A0block_job_cancel(job);
>>> > + =A0 =A0while (bs->job !=3D NULL && bs->job->busy) {
>> It's not clear to me why we have a busy flag.
>
> Because the coroutine does not restart if you do qemu_aio_wait and the
> coroutine is waiting in co_sleep. =A0So the busy flag communicates that
> the coroutine is quiescent and, when cancelled, will not issue any new I/=
O.

Ah, yes.  This is tricky, a comment would be nice.

Stefan