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effd60c878
monitor_qmp_dispatcher_co() runs in the iohandler AioContext that is not
polled during nested event loops. The coroutine currently reschedules
itself in the main loop's qemu_aio_context AioContext, which is polled
during nested event loops. One known problem is that QMP device-add
calls drain_call_rcu(), which temporarily drops the BQL, leading to all
sorts of havoc like other vCPU threads re-entering device emulation code
while another vCPU thread is waiting in device emulation code with
aio_poll().
Paolo Bonzini suggested running non-coroutine QMP handlers in the
iohandler AioContext. This avoids trouble with nested event loops. His
original idea was to move coroutine rescheduling to
monitor_qmp_dispatch(), but I resorted to moving it to qmp_dispatch()
because we don't know if the QMP handler needs to run in coroutine
context in monitor_qmp_dispatch(). monitor_qmp_dispatch() would have
been nicer since it's associated with the monitor implementation and not
as general as qmp_dispatch(), which is also used by qemu-ga.
A number of qemu-iotests need updated .out files because the order of
QMP events vs QMP responses has changed.
Solves Issue #1933.
Cc: qemu-stable@nongnu.org
Fixes: 7bed89958b ("device_core: use drain_call_rcu in in qmp_device_add")
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2215192
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2214985
Buglink: https://issues.redhat.com/browse/RHEL-17369
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20240118144823.1497953-4-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
59 lines
1.8 KiB
Plaintext
59 lines
1.8 KiB
Plaintext
QA output created by 182
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432
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Starting QEMU
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Starting a second QEMU using the same image should fail
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QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=none,id=drive0,file.locking=on: Failed to get "write" lock
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Is another process using the image [TEST_DIR/t.qcow2]?
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=== Testing reopen ===
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{'execute': 'qmp_capabilities'}
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{"return": {}}
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{'execute': 'blockdev-add',
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'arguments': {
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'node-name': 'node0',
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'driver': 'file',
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'filename': 'TEST_DIR/t.IMGFMT',
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'locking': 'on'
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} }
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{"return": {}}
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{'execute': 'blockdev-snapshot-sync',
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'arguments': {
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'node-name': 'node0',
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'snapshot-file': 'TEST_DIR/t.IMGFMT.overlay',
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'snapshot-node-name': 'node1'
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} }
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Formatting 'TEST_DIR/t.qcow2.overlay', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=197120 backing_file=TEST_DIR/t.qcow2 backing_fmt=file lazy_refcounts=off refcount_bits=16
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{"return": {}}
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{'execute': 'blockdev-add',
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'arguments': {
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'node-name': 'node1',
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'driver': 'file',
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'filename': 'TEST_DIR/t.IMGFMT',
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'locking': 'on'
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} }
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{"return": {}}
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{'execute': 'nbd-server-start',
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'arguments': {
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'addr': {
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'type': 'unix',
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'data': {
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'path': 'SOCK_DIR/nbd.socket'
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} } } }
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{"return": {}}
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{'execute': 'nbd-server-add',
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'arguments': {
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'device': 'node1'
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} }
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{"return": {}}
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=== Testing failure to loosen restrictions ===
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{'execute': 'qmp_capabilities'}
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{"return": {}}
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{'execute': 'quit'}
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{"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
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{"return": {}}
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*** done
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