Am 24.08.2018 um 09:22 hat Fam Zheng geschrieben:
> On Fri, 08/17 19:02, Kevin Wolf wrote:
> > Simimlar to AIO_WAIT_WHILE(), job_finish_sync() needs to release the
> > AioContext lock of the job before calling aio_poll(). Otherwise,
> > callbacks called by aio_poll() would possibly take the lock a second
> > time and run into a deadlock with a nested AIO_WAIT_WHILE() call.
> >
> > Signed-off-by: Kevin Wolf <kw...@redhat.com>
> > ---
> > job.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/job.c b/job.c
> > index a746bfe70b..6acf55bceb 100644
> > --- a/job.c
> > +++ b/job.c
> > @@ -1016,7 +1016,10 @@ int job_finish_sync(Job *job, void (*finish)(Job *,
> > Error **errp), Error **errp)
> > job_drain(job);
> > }
> > while (!job_is_completed(job)) {
> > + AioContext *aio_context = job->aio_context;
> > + aio_context_release(aio_context);
> > aio_poll(qemu_get_aio_context(), true);
> > + aio_context_acquire(aio_context);
> > }
> > ret = (job_is_cancelled(job) && job->ret == 0) ? -ECANCELED : job->ret;
> > job_unref(job);
>
> Why doesn't this function just use AIO_WAIT_WHILE()?
I don't have an AioWait here, so this seemed the simplest way. But
thinking more about it, a dummy AioWait should do because otherwise the
code would already hang as it is.
Of course, we need to #include "block/aio-wait.h", which doesn't feel
completely right outside the block layer. But maybe that just means that
the header should be moved somewhere else.
Kevin
