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When the backend domain crashes, coordinated device cleanup is not possible (as it involves waiting for the backend state change). In that case, toolstack forcefully removes frontend xenstore entries. xenbus_dev_changed() handles this case, and triggers device cleanup. It's possible that toolstack manages to connect new device in that place, before xenbus_dev_changed() notices the old one is missing. If that happens, new one won't be probed and will forever remain in XenbusStateInitialising. Fix this by checking the frontend's state in Xenstore. In case it has been reset to XenbusStateInitialising by Xen tools, consider this being the result of an unplug+plug operation. It's important that cleanup on such unplug doesn't modify Xenstore entries (especially the "state" key) as it belong to the new device to be probed - changing it would derail establishing connection to the new backend (most likely, closing the device before it was even connected). Handle this case by setting new xenbus_device->vanished flag to true, and check it before changing state entry. And even if xenbus_dev_changed() correctly detects the device was forcefully removed, the cleanup handling is still racy. Since this whole handling doesn't happened in a single Xenstore transaction, it's possible that toolstack might put a new device there already. Avoid re-creating the state key (which in the case of loosing the race would actually close newly attached device). The problem does not apply to frontend domain crash, as this case involves coordinated cleanup. Problem originally reported at https://lore.kernel.org/xen-devel/aOZvivyZ9YhVWDLN@mail-itl/T/#t, including reproduction steps. Based-on-patch-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20260218095205.453657-3-jgross@suse.com> |
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| .. | ||
| arm | ||
| interface | ||
| acpi.h | ||
| balloon.h | ||
| events.h | ||
| features.h | ||
| grant_table.h | ||
| hvc-console.h | ||
| hvm.h | ||
| mem-reservation.h | ||
| page.h | ||
| pci.h | ||
| platform_pci.h | ||
| swiotlb-xen.h | ||
| xen-front-pgdir-shbuf.h | ||
| xen-ops.h | ||
| xen.h | ||
| xenbus.h | ||
| xenbus_dev.h | ||