Re: [PATCH v3 for-10.2 00/13] Fix deadlock with bdrv_open of self-served NBD

["Daniel P. Berrangé" <berrange@redhat.com>]

Seems you sent a v3 twice today. I reviewed the earlier v3 and
assume this v3 is an identical accident dupe. If this is actually
a v3 let me know and i'll review further...

On Wed, Nov 12, 2025 at 07:11:25PM -0600, Eric Blake wrote:
> v2 was here:
> https://lists.nongnu.org/archive/html/qemu-devel/2025-11/msg01243.html
> 
> Since then:
>  - drop patch 7/12; refcounting for GSource case is now unchanged
>  - add a couple of patches: fix a chardev leaky abstraction, and add a
>    mutex lock for cross-thread safety
>  - improve commit messages to document why NBD is safe now, even without
>    adding notify callbacks to AioContext
> 
> Now that the new behavior is opt-in rather than a change of defaults,
> and only NBD opts in, it should still be safe to include in 10.2.
> But the technical debt here means that we really should consider
> improving the AioContext API for 11.0 to allow for a notify function
> similar to what GSource provides.
> 
> Key:
> [----] : patches are identical
> [####] : number of functional differences between upstream/downstream patch
> [down] : patch is downstream-only
> The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
> 
> 001/13:[----] [--] 'iotests: Drop execute permissions on vvfat.out'
> 002/13:[----] [--] 'qio: Add trace points to net_listener'
> 003/13:[----] [--] 'qio: Unwatch before notify in QIONetListener'
> 004/13:[----] [--] 'qio: Remember context of qio_net_listener_set_client_func_full'
> 005/13:[down] 'qio: Protect NetListener callback with mutex'
> 006/13:[----] [-C] 'qio: Minor optimization when callback function is unchanged'
> 007/13:[0042] [FC] 'qio: Factor out helpers qio_net_listener_[un]watch'
> 008/13:[down] 'chardev: Reuse channel's cached local address'
> 009/13:[0053] [FC] 'qio: Provide accessor around QIONetListener->sioc'
> 010/13:[0013] [FC] 'qio: Prepare NetListener to use AioContext'
> 011/13:[0041] [FC] 'qio: Add QIONetListener API for using AioContext'
> 012/13:[----] [--] 'nbd: Avoid deadlock in client connecting to same-process server'
> 013/13:[----] [--] 'iotests: Add coverage of recent NBD qio deadlock fix'
> 
> Eric Blake (13):
>   iotests: Drop execute permissions on vvfat.out
>   qio: Add trace points to net_listener
>   qio: Unwatch before notify in QIONetListener
>   qio: Remember context of qio_net_listener_set_client_func_full
>   qio: Protect NetListener callback with mutex
>   qio: Minor optimization when callback function is unchanged
>   qio: Factor out helpers qio_net_listener_[un]watch
>   chardev: Reuse channel's cached local address
>   qio: Provide accessor around QIONetListener->sioc
>   qio: Prepare NetListener to use AioContext
>   qio: Add QIONetListener API for using AioContext
>   nbd: Avoid deadlock in client connecting to same-process server
>   iotests: Add coverage of recent NBD qio deadlock fix
> 
>  include/io/channel-socket.h                   |   2 +-
>  include/io/net-listener.h                     |  71 ++++-
>  blockdev-nbd.c                                |   4 +-
>  chardev/char-socket.c                         |   2 +-
>  io/net-listener.c                             | 300 +++++++++++++-----
>  migration/socket.c                            |   4 +-
>  ui/vnc.c                                      |  34 +-
>  io/trace-events                               |   5 +
>  tests/qemu-iotests/tests/nbd-in-qcow2-chain   |  94 ++++++
>  .../qemu-iotests/tests/nbd-in-qcow2-chain.out |  75 +++++
>  tests/qemu-iotests/tests/vvfat.out            |   0
>  11 files changed, 498 insertions(+), 93 deletions(-)
>  create mode 100755 tests/qemu-iotests/tests/nbd-in-qcow2-chain
>  create mode 100644 tests/qemu-iotests/tests/nbd-in-qcow2-chain.out
>  mode change 100755 => 100644 tests/qemu-iotests/tests/vvfat.out
> 
> -- 
> 2.51.1
> 

With regards,
Daniel
-- 
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