qemu /
qemu /
6910f04aa646f63a0257f77201ad8ea15992b816 hw/scsi: avoid deadlock upon TMF request cancelling with VirtIO
When scsi_req_dequeue() is reached via
scsi_req_cancel_async()
virtio_scsi_tmf_cancel_req()
virtio_scsi_do_tmf_aio_context(),
there is a deadlock when trying to acquire the SCSI device's requests
lock, because it was already acquired in
virtio_scsi_do_tmf_aio_context().
In particular, the issue happens with a FreeBSD guest (13, 14, 15,
maybe more), when it cancels SCSI requests, because of timeout.
This is a regression caused by commit da6eebb33b ("virtio-scsi:
perform TMFs in appropriate AioContexts") and the introduction of the
requests_lock earlier.
To fix the issue, only cancel the requests after releasing the
requests_lock. For this, the SCSI device's requests are iterated while
holding the requests_lock and the requests to be cancelled are
collected in a list. Then, the collected requests are cancelled
one by one while not holding the requests_lock. This is safe, because
only requests from the current AioContext are collected and acted
upon.
Originally reported by Proxmox VE users:
https://bugzilla.proxmox.com/show_bug.cgi?id=6810
https://forum.proxmox.com/threads/173914/
Fixes: da6eebb33b ("virtio-scsi: perform TMFs in appropriate AioContexts")
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-id: 20251017094518.328905-1-f.ebner@proxmox.com
[Changed g_list_append() to g_list_prepend() to avoid traversing the
list each time.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 file changed
