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Re: [Qemu-block] [PATCH v3] virtio-blk: schedule virtio_notify_config to
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH v3] virtio-blk: schedule virtio_notify_config to run on main context |
Date: |
Fri, 20 Sep 2019 10:14:48 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
On Mon, Sep 16, 2019 at 01:24:12PM +0200, Sergio Lopez wrote:
> virtio_notify_config() needs to acquire the global mutex, which isn't
> allowed from an iothread, and may lead to a deadlock like this:
>
> - main thead
> * Has acquired: qemu_global_mutex.
> * Is trying the acquire: iothread AioContext lock via
> AIO_WAIT_WHILE (after aio_poll).
>
> - iothread
> * Has acquired: AioContext lock.
> * Is trying to acquire: qemu_global_mutex (via
> virtio_notify_config->prepare_mmio_access).
>
> If virtio_blk_resize() is called from an iothread, schedule
> virtio_notify_config() to be run in the main context BH.
>
> Signed-off-by: Sergio Lopez <address@hidden>
> ---
> Changelog
>
> v3:
> - Unconditionally schedule the work to be done in the main context BH
> (thanks John Snow and Kevin Wolf).
>
> v2:
> - Use aio_bh_schedule_oneshot instead of scheduling a coroutine
> (thanks Kevin Wolf).
> - Switch from RFC to v2 patch.
> ---
> hw/block/virtio-blk.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block
Stefan
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