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>
81 lines
1.5 KiB
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81 lines
1.5 KiB
Plaintext
QA output created by 195
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Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
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Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
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Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
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Change backing file of mid (opened read-only)
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Testing: -drive if=none,file=TEST_DIR/t.IMGFMT,backing.node-name=mid
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{
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QMP_VERSION
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}
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{
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"return": {
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}
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}
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{
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"return": {
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}
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}
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{
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"timestamp": {
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"seconds": TIMESTAMP,
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"microseconds": TIMESTAMP
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},
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"event": "SHUTDOWN",
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"data": {
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"guest": false,
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"reason": "host-qmp-quit"
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}
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}
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{
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"return": {
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}
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}
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image: TEST_DIR/t.IMGFMT.mid
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file format: IMGFMT
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virtual size: 64 MiB (67108864 bytes)
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cluster_size: 65536
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backing file: /dev/null
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backing file format: IMGFMT
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Change backing file of top (opened writable)
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Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
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Testing: -drive if=none,file=TEST_DIR/t.IMGFMT,node-name=top
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{
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QMP_VERSION
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}
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{
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"return": {
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}
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}
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{
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"return": {
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}
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}
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{
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"timestamp": {
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"seconds": TIMESTAMP,
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"microseconds": TIMESTAMP
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},
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"event": "SHUTDOWN",
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"data": {
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"guest": false,
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"reason": "host-qmp-quit"
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}
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}
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{
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"return": {
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}
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}
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image: TEST_DIR/t.IMGFMT
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file format: IMGFMT
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virtual size: 64 MiB (67108864 bytes)
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cluster_size: 65536
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backing file: /dev/null
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backing file format: IMGFMT
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*** done
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