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This fixes devices like IDE that can still start new requests from I/O handlers in the CPU thread while the block backend is drained. The basic assumption is that in a drain section, no new requests should be allowed through a BlockBackend (blk_drained_begin/end don't exist, we get drain sections only on the node level). However, there are two special cases where requests should not be queued: 1. Block jobs: We already make sure that block jobs are paused in a drain section, so they won't start new requests. However, if the drain_begin is called on the job's BlockBackend first, it can happen that we deadlock because the job stays busy until it reaches a pause point - which it can't if its requests aren't processed any more. The proper solution here would be to make all requests through the job's filter node instead of using a BlockBackend. For now, just disabling request queuing on the job BlockBackend is simpler. 2. In test cases where making requests through bdrv_* would be cumbersome because we'd need a BdrvChild. As we already got the functionality to disable request queuing from 1., use it in tests, too, for convenience. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> |
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| authz | ||
| block | ||
| chardev | ||
| crypto | ||
| disas | ||
| exec | ||
| fpu | ||
| hw | ||
| io | ||
| libdecnumber | ||
| migration | ||
| monitor | ||
| net | ||
| qapi | ||
| qemu | ||
| qom | ||
| scsi | ||
| standard-headers | ||
| sysemu | ||
| ui | ||
| elf.h | ||
| glib-compat.h | ||
| qemu-common.h | ||
| qemu-io.h | ||
| trace-tcg.h | ||