Re: [PATCH 01/12] virtio-scsi: replace AioContext lock with tmf_bh_lock

[Stefan Hajnoczi]

On Mon, Dec 04, 2023 at 01:46:13PM +0100, Kevin Wolf wrote:
> Am 29.11.2023 um 20:55 hat Stefan Hajnoczi geschrieben:
> > Protect the Task Management Function BH state with a lock. The TMF BH
> > runs in the main loop thread. An IOThread might process a TMF at the
> > same time as the TMF BH is running. Therefore tmf_bh_list and tmf_bh
> > must be protected by a lock.
> > 
> > Run TMF request completion in the IOThread using aio_wait_bh_oneshot().
> > This avoids more locking to protect the virtqueue and SCSI layer state.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> 
> The second part reminds me that the implicit protection of the virtqueue
> and SCSI data structures by having all accesses in a single thread is
> hard to review and I think we wanted to put some assertions there to
> check that we're really running in the right thread. I don't think we
> have done that so far, so I suppose after this patch would be the place
> in the series to add them, before we remove the protection by the
> AioContext lock?

Thanks for reminding me. I will add assertions in the next revision of
this series.

Stefan

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