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If a BDS gets deleted during blk_drain_all(), it might miss a call to bdrv_do_drained_end(). This means missing a call to aio_enable_external() and the AIO context remains disabled for ever. This can cause a device to become irresponsive and to disrupt the guest execution, ie. hang, loop forever or worse. This scenario is quite easy to encounter with virtio-scsi on POWER when punching multiple blockdev-create QMP commands while the guest is booting and it is still running the SLOF firmware. This happens because SLOF disables/re-enables PCI devices multiple times via IO/MEM/MASTER bits of PCI_COMMAND register after the initial probe/feature negotiation, as it tends to work with a single device at a time at various stages like probing and running block/network bootloaders without doing a full reset in-between. This naturally generates many dataplane stops and starts, and thus many drain sections that can race with blockdev_create_run(). In the end, SLOF bails out. It is somehow reproducible on x86 but it requires to generate articial dataplane start/stop activity with stop/cont QMP commands. In this case, seabios ends up looping for ever, waiting for the virtio-scsi device to send a response to a command it never received. Add a helper that pairs all previously called bdrv_do_drained_begin() with a bdrv_do_drained_end() and call it from bdrv_close(). While at it, update the "/bdrv-drain/graph-change/drain_all" test in test-bdrv-drain so that it can catch the issue. BugId: https://bugzilla.redhat.com/show_bug.cgi?id=1874441 Signed-off-by: Greg Kurz <groug@kaod.org> Message-Id: <160346526998.272601.9045392804399803158.stgit@bahia.lan> Signed-off-by: Kevin Wolf <kwolf@redhat.com> |
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| .. | ||
| accounting.h | ||
| aio_task.h | ||
| aio-wait.h | ||
| aio.h | ||
| block_backup.h | ||
| block_int.h | ||
| block-copy.h | ||
| block-hmp-cmds.h | ||
| block.h | ||
| blockjob_int.h | ||
| blockjob.h | ||
| dirty-bitmap.h | ||
| export.h | ||
| nbd.h | ||
| nvme.h | ||
| qapi.h | ||
| qdict.h | ||
| raw-aio.h | ||
| snapshot.h | ||
| thread-pool.h | ||
| throttle-groups.h | ||
| write-threshold.h | ||